Globally, parasitic infections hinder aquaculture productivity and sustainability. Improper water... more Globally, parasitic infections hinder aquaculture productivity and sustainability. Improper water quality parameters reduce fish immunity, make them susceptible to parasites, and enhance parasitic proliferation in culture systems. Subsequently, this study aimed to determine the prevalence and intensity of ecto-and endo-parasite infesting Oreochromis niloticus in varying water quality in aquaculture systems in Kericho, Bomet, and Nakuru counties. A total of 220 Oreochromis niloticus samples were captured from 11 liner ponds, eight earthen ponds, two concrete ponds, and one plastic tank from 22 farms in the three counties. External and internal organs were examined for parasite infestation. Skin scrapings and squash preparation of fish eyes were also examined to reveal the organisms through microscopic examination. A Pearson's correlation analysis between physicochemical parameters and parasitic prevalence was used to determine the strength and direction of correlation coefficients with significance at 95%. Overall parasitic prevalence infestation was 39.6% (87/220). Ten parasite genera were recovered, with Dactylogyrus species dominating overall at 15.9% (35/220), followed by Trichodina spp. (7.7%; 17/220). Epistylis species had the highest mean intensity of 12.8 AE 35.7 (total number of Epistylis parasites (141)/total of infested fish (11)). Earthen ponds had a significantly higher (36.2%, 29/80) prevalence of Dactylogyrus sp. than liner ponds (3.6%, 4/110) (p<0:001). Dissolved oxygen levels were 16.9 AE 0.7 mgL −1 in Bomet, 14.9 AE 0.3 mgL −1 in Kericho, and 12.5 AE 0.5 mgL −1 in Nakuru which were above desirable range for fish culture. The electrical conductivity in Bomet was 76 AE 5 µS/cm and Kericho 52 AE 4 µS/cm below the desirable range. Temperature, pH, phosphate, nitrates, and nitrites were within the desirable limit for fish farming. Electrical conductivity and pH had positive correlation of 1 and 0.97, respectively, with the prevalence of Acanthocephalus, Euclinostomum, and Trichodina species. Temperature and nitrate positively correlated between 0.80-0.89 and 0.90-0.99, respectively, with the prevalence of Dactylogyrus, Riboscyphidia, Epistylis, Camallanus, and Paracamallanus species. The study demonstrates that water quality significantly influences parasitic prevalence in aquaculture systems. Therefore, it is crucial for farmers to monitor water quality parameters to mitigate parasitic infestations.
Globally, parasitic infections hinder aquaculture productivity and sustainability. Improper water... more Globally, parasitic infections hinder aquaculture productivity and sustainability. Improper water quality parameters reduce fish immunity, make them susceptible to parasites, and enhance parasitic proliferation in culture systems. Subsequently, this study aimed to determine the prevalence and intensity of ecto-and endo-parasite infesting Oreochromis niloticus in varying water quality in aquaculture systems in Kericho, Bomet, and Nakuru counties. A total of 220 Oreochromis niloticus samples were captured from 11 liner ponds, eight earthen ponds, two concrete ponds, and one plastic tank from 22 farms in the three counties. External and internal organs were examined for parasite infestation. Skin scrapings and squash preparation of fish eyes were also examined to reveal the organisms through microscopic examination. A Pearson's correlation analysis between physicochemical parameters and parasitic prevalence was used to determine the strength and direction of correlation coefficients with significance at 95%. Overall parasitic prevalence infestation was 39.6% (87/220). Ten parasite genera were recovered, with Dactylogyrus species dominating overall at 15.9% (35/220), followed by Trichodina spp. (7.7%; 17/220). Epistylis species had the highest mean intensity of 12.8 AE 35.7 (total number of Epistylis parasites (141)/total of infested fish (11)). Earthen ponds had a significantly higher (36.2%, 29/80) prevalence of Dactylogyrus sp. than liner ponds (3.6%, 4/110) (p<0:001). Dissolved oxygen levels were 16.9 AE 0.7 mgL −1 in Bomet, 14.9 AE 0.3 mgL −1 in Kericho, and 12.5 AE 0.5 mgL −1 in Nakuru which were above desirable range for fish culture. The electrical conductivity in Bomet was 76 AE 5 µS/cm and Kericho 52 AE 4 µS/cm below the desirable range. Temperature, pH, phosphate, nitrates, and nitrites were within the desirable limit for fish farming. Electrical conductivity and pH had positive correlation of 1 and 0.97, respectively, with the prevalence of Acanthocephalus, Euclinostomum, and Trichodina species. Temperature and nitrate positively correlated between 0.80-0.89 and 0.90-0.99, respectively, with the prevalence of Dactylogyrus, Riboscyphidia, Epistylis, Camallanus, and Paracamallanus species. The study demonstrates that water quality significantly influences parasitic prevalence in aquaculture systems. Therefore, it is crucial for farmers to monitor water quality parameters to mitigate parasitic infestations.
Campylobacter is a zoonotic foodborne pathogen that is often linked with gastroenteritis and othe... more Campylobacter is a zoonotic foodborne pathogen that is often linked with gastroenteritis and other extraintestinal infections in humans. This study is aimed at determining the genetic determinants of virulence-encoding genes responsible for flagellin motility protein A (flaA), Campylobacter adhesion to fibronectin F (cadF), Campylobacter invasion antigen B (ciaB) and cytolethal distending toxin (cdt) A (cdtA) in Campylobacter species. A total of 29 Campylobacter coli isolates (16 from cattle, 9from chicken, and 4 from water samples) and 74 Campylobacter jejuni isolates (38 from cattle, 30 from chicken, and 6 from water samples) described in an earlier study in Kajiado County, Kenya, were examined for the occurrence of virulence-associated genes using polymerase chain reaction (PCR) and amplicon sequencing. The correlations among virulence genes were analyzed using Pearson’s correlation coefficient (R) method. Among the 103 Campylobacter strains screened, 89 were found to harbour a single or multiple virulence gene(s), giving an overall prevalence of 86.4%. C. jejuni strains had the highest prevalence of multivirulence at 64.9% (48/74), compared to C. coli (58.6%, 17/29). The ciaB and flaA genes were the most common virulence genes detected in C. jejuni (81.1% [60/74] and 62.2% [46/74], respectively) and in C. coli (each at 62.1%;18/29). Campylobacter isolates from chicken harboured the most virulence-encoding genes. C. jejuni strains from chicken and cattle harboured the highest proportions of the cdtA and ciaB genes, respectively. All the C. coli strains from water samples harboured the cadF and flaA genes. The results obtained further revealed a significant positive correlation between cadF and flaA (R = 0 733). C. jejuni and C. coli strains from cattle, chicken, and water harbour virulence markers responsible for motility/colonization, invasion, adherence, and toxin production, evoking their important role in campylobacteriosis development among humans and livestock. The identification of cattle, chicken, and water samples as reservoirs of virulent Campylobacter spp. highlights the possible risk to human health. These data on some virulence genes of Campylobacter will assist food safety and public health officials in formulating policy statements. Keywords: Campylobacter; campylobacteriosis; foodborne; livestock; multiple virulence genes; public health; zoonotic
Management practices and risk factors associated with parasitic infestations in farmed Nile tilapia in Bomet and Kericho counties, Kenya, 2024
The aquaculture has surged in Kenya owing to dwindling wild stocks. However, this is coupled with... more The aquaculture has surged in Kenya owing to dwindling wild stocks. However, this is coupled with challenges such as limited fish health knowledge and biosecurity measures. A cross sectional study was undertaken to determine risk factors and management practices associated with parasitic infestation of farmed Nile tilapia in Bomet and Kericho counties, Kenya. A total of 150 Nile tilapia (Oreochromis niloticus) were collected and subjected to standard parasitological examination. Potential risk factors associated with parasitic infestation in fish were assessed in 88 farms using pretested semi-structured questionnaires and on-site farm visit observations. Logistic regression analysis with the estimation of odds ratios (OR) was used to assess potential risks factors. Tilapia were dominant fish (>95%) and were farmed mainly in earthen ponds (> 61%). Most farmers (52.3%) used river water for ponds and 14% had experienced floods that introduced predators in the ponds. Farmers relied on fisheries department harvesting nets and only 12.5% sun dried the nets after use. Few farmers (37.5%) frequently cleaned and dried ponds before restocking, while 34.1% did not remove the pond bottom soil after fish harvesting. Approximately 3.4% of the farmers rated diseases as the main obstacle in fish farming and, 68.2% could not identify sick fish. Those who identified sick fish reported abnormal swimming (23.9%) and mortality (8%). Out of the 150 fish sampled, 62 (prevalence = 42%) were found to be infected with different genera of parasites including: Dactylogyrus spp. (21%); Epistylis spp. (7.3%); Riboscyphidia spp. (6.7%); Trichodina spp. (6%); Paracamallanus spp. (4.7%); Camallanus spp. (2%); Diplostomum spp. (2%) and Contracaecum spp. (1.3%). Dactylogyrus spp. were common in earthen ponds (91%) (p<0.001). Some management practices identified as possible risk factors for parasitic infestation in fish included; pond fertilization using livestock manure (OR=5.633), siting fish ponds in valleys/gullies (OR=2.028), use of river water for aqua farming (OR=1.654) and earthen pond types (OR=2.023). Farmers and extension workers should be trained on the importance of fish health and biosecurity. The authors recommend further detailed longitudinal controlled studies which consider myriad fish husbandry practices with parasitic infestations.
International Journal of Fisheries and Aquatic Studies, 2024
Bacterial infections can cause latent, low to high mortalities in aquaculture farms and wild fish... more Bacterial infections can cause latent, low to high mortalities in aquaculture farms and wild fish while some bacteria may be zoonotic. This study isolated, characterized and identify potential pathogenic and zoonotic aerobic bacteria in farmed and wild Oreochromis jipe, O. niloticus, their hybrids and culture water source from Taita-Taveta County. One hundred and eleven apparently healthy-appearing fish consisting of 67 O. jipe, 34 O. niloticus and 10 hybrids and nine water (7 farms and 2 Lake Jipe) samples were processed. Samples were aseptically collected from each fish, namely, skin and kidney swabs; gills and intestinal tissues. Conventional culture, biochemical and Matrix Assisted Laser Desorption/Ionization Time of Flight Mass Spectrometry tests were done to identify isolated bacteria. A total of 596 bacterial isolates representing 22 genera were recovered from 444 fish organs and 9 water samples. Of these, the highest numbers were from the gills at 29.7% followed by skin 29.6%, intestines 24.4%, kidney 11.8% and the least from water at 4.7%. Potential fish pathogens were Bacillus cereus (8%), Aeromonas veronii (8%), Aeromonas hydrophila (5%), Lysinibacillus fusiformis (5%), Acinetobacter Johnsonii (4%) and Acinetobacter solii (4%). Potential pathogenic and zoonotic bacteria isolated were Staphylococcus lentus 17.9% (5/28), Aeromonas hydrophila 10.7% (3/28) and Aeromonas hormaechei 7.1% (2/28). From the sampling site; 28.4% (169/596) of the total isolates were collected from Taveta, then Mwatate with 26.9% (160/596), Mkwajuni 16.8%, (98/596), Kenya Wildlife Service 7.0% (42/596), Wundanyi 6.7% (40/596), Voi 6.6% (39/596) and the inlet of the Lake Jipe had a 3.2% (19/596) and from the water samples 4.7% (28/596). These findings confirm that fish in aquaculture farms, wild fish and water used for aquaculture harbors potentially pathogenic and zoonotic bacteria which may cause fish diseases and pose public health risks. Extension officers and farmers need awareness on mitigation measures against these pathogens.
International Journal of Fisheries and Aquatic Studies 2024; 12(4): 49-58, 2024
Bacterial infections can cause latent, low to high mortalities in aquaculture farms and wild fish... more Bacterial infections can cause latent, low to high mortalities in aquaculture farms and wild fish while some bacteria may be zoonotic. This study isolated, characterized and identify potential pathogenic and zoonotic aerobic bacteria in farmed and wild Oreochromis jipe, O. niloticus, their hybrids and culture water source from Taita-Taveta County. One hundred and eleven apparently healthy-appearing fish consisting of 67 O. jipe, 34 O. niloticus and 10 hybrids and nine water (7 farms and 2 Lake Jipe) samples were processed. Samples were aseptically collected from each fish, namely, skin and kidney swabs; gills and intestinal tissues. Conventional culture, biochemical and Matrix Assisted Laser Desorption/Ionization Time of Flight Mass Spectrometry tests were done to identify isolated bacteria. A total of 596 bacterial isolates representing 22 genera were recovered from 444 fish organs and 9 water samples. Of these, the highest numbers were from the gills at 29.7% followed by skin 29.6%, intestines 24.4%, kidney 11.8% and the least from water at 4.7%. Potential fish pathogens were Bacillus cereus (8%), Aeromonas veronii (8%), Aeromonas hydrophila (5%), Lysinibacillus fusiformis (5%), Acinetobacter Johnsonii (4%) and Acinetobacter solii (4%). Potential pathogenic and zoonotic bacteria isolated were Staphylococcus lentus 17.9% (5/28), Aeromonas hydrophila 10.7% (3/28) and Aeromonas hormaechei 7.1% (2/28). From the sampling site; 28.4% (169/596) of the total isolates were collected from Taveta, then Mwatate with 26.9% (160/596), Mkwajuni 16.8%, (98/596), Kenya Wildlife Service 7.0% (42/596), Wundanyi 6.7% (40/596), Voi 6.6% (39/596) and the inlet of the Lake Jipe had a 3.2% (19/596) and from the water samples 4.7% (28/596). These findings confirm that fish in aquaculture farms, wild fish and water used for aquaculture harbors potentially pathogenic and zoonotic bacteria which may cause fish diseases and pose public health risks. Extension officers and farmers need awareness on mitigation measures against these pathogens.
International Journal of Fisheries and Aquatic Studies , 2024
Bacterial infections can cause latent, low to high mortalities in aquaculture farms and wild fish... more Bacterial infections can cause latent, low to high mortalities in aquaculture farms and wild fish while some bacteria may be zoonotic. This study isolated, characterized and identify potential pathogenic and zoonotic aerobic bacteria in farmed and wild Oreochromis jipe, O. niloticus, their hybrids and culture water source from Taita-Taveta County. One hundred and eleven apparently healthy-appearing fish consisting of 67 O. jipe, 34 O. niloticus and 10 hybrids and nine water (7 farms and 2 Lake Jipe) samples were processed. Samples were aseptically collected from each fish, namely, skin and kidney swabs; gills and intestinal tissues. Conventional culture, biochemical and Matrix Assisted Laser Desorption/Ionization Time of Flight Mass Spectrometry tests were done to identify isolated bacteria. A total of 596 bacterial isolates representing 22 genera were recovered from 444 fish organs and 9 water samples. Of these, the highest numbers were from the gills at 29.7% followed by skin 29.6%, intestines 24.4%, kidney 11.8% and the least from water at 4.7%. Potential fish pathogens were Bacillus cereus (8%), Aeromonas veronii (8%), Aeromonas hydrophila (5%), Lysinibacillus fusiformis (5%), Acinetobacter Johnsonii (4%) and Acinetobacter solii (4%). Potential pathogenic and zoonotic bacteria isolated were Staphylococcus lentus 17.9% (5/28), Aeromonas hydrophila 10.7% (3/28) and Aeromonas hormaechei 7.1% (2/28). From the sampling site; 28.4% (169/596) of the total isolates were collected from Taveta, then Mwatate with 26.9% (160/596), Mkwajuni 16.8%, (98/596), Kenya Wildlife Service 7.0% (42/596), Wundanyi 6.7% (40/596), Voi 6.6% (39/596) and the inlet of the Lake Jipe had a 3.2% (19/596) and from the water samples 4.7% (28/596). These findings confirm that fish in aquaculture farms, wild fish and water used for aquaculture harbors potentially pathogenic and zoonotic bacteria which may cause fish diseases and pose public health risks. Extension officers and farmers need awareness on mitigation measures against these pathogens. Keywords: Aeromonas hydrophila, aquaculture, fish pathogens, prevalence, wild fish, Zoonosis
International Journal of Fisheries and Aquatic Studies, 2024
The aquaculture has surged in Kenya owing to dwindling wild stocks. However, this is coupled with... more The aquaculture has surged in Kenya owing to dwindling wild stocks. However, this is coupled with challenges such as limited fish health knowledge and biosecurity measures. A cross sectional study was undertaken to determine risk factors and management practices associated with parasitic infestation of farmed Nile tilapia in Bomet and Kericho counties, Kenya. A total of 150 Nile tilapia (Oreochromis niloticus) were collected and subjected to standard parasitological examination. Potential risk factors associated with parasitic infestation in fish were assessed in 88 farms using pretested semi-structured questionnaires and on-site farm visit observations. Logistic regression analysis with the estimation of odds ratios (OR) was used to assess potential risks factors. Tilapia were dominant fish (>95%) and were farmed mainly in earthen ponds (> 61%). Most farmers (52.3%) used river water for ponds and 14% had experienced floods that introduced predators in the ponds. Farmers relied on fisheries department harvesting nets and only 12.5% sun dried the nets after use. Few farmers (37.5%) frequently cleaned and dried ponds before restocking, while 34.1% did not remove the pond bottom soil after fish harvesting. Approximately 3.4% of the farmers rated diseases as the main obstacle in fish farming and, 68.2% could not identify sick fish. Those who identified sick fish reported abnormal swimming (23.9%) and mortality (8%). Out of the 150 fish sampled, 62 (prevalence = 42%) were found to be infected with different genera of parasites including: Dactylogyrus spp. (21%); Epistylis spp. (7.3%); Riboscyphidia spp. (6.7%); Trichodina spp. (6%); Paracamallanus spp. (4.7%); Camallanus spp. (2%); Diplostomum spp. (2%) and Contracaecum spp. (1.3%). Dactylogyrus spp. were common in earthen ponds (91%) (p<0.001). Some management practices identified as possible risk factors for parasitic infestation in fish included; pond fertilization using livestock manure (OR=5.633), siting fish ponds in valleys/gullies (OR=2.028), use of river water for aqua farming (OR=1.654) and earthen pond types (OR=2.023). Farmers and extension workers should be trained on the importance of fish health and biosecurity. The authors recommend further detailed longitudinal controlled studies which consider myriad fish husbandry practices with parasitic infestations. Keywords: Biosecurity, fish health, management practices, nile tilapia
Integrated farms are smallholder farms that rear a mixture of different food animals in close pro... more Integrated farms are smallholder farms that rear a mixture of different food animals in close proximity. Subsequently, a survey was carried out to establish two aspects: (1) occurrence rate of thermophilic Campylobacter in cattle in 55 integrated small-scale farms within Kajiado County; a total of 265 cattle rectal swabs were randomly collected for bacterial isolation, and (2) factors associated with Campylobacter occurrence; these included administration of pre-tested questionnaires, to collect data on respective farm characteristics and management practices, and isolation of Campylobacter from respective water and chicken cloacal swabs (as possible sources of infection). The collected rectal/cloacal swabs and water samples were specifically processed for Campylobacter isolation, followed by confirmation using a singleplex polymerase chain reaction (PCR) assay, while the questionnaire data was analyzed using logistic regression models. Campylobacters in cattle were detected in 72.7% (95% confidence interval (95%CI) =60.9-84.5) of the surveyed farms. The farm/herd level Campylobacter positivity ranged from 12.5% to 100%; 27.3% (95%CI=15.5-39.1) of the surveyed farms were Campylobacter negative. Of the Campylobacter positive farms, the mean prevalence was 48.14%, with a median of 50%. Farm stocking dairy breeds [adjusted odds ratio (AOR)=12.7, 95%CI: 3.2-60], presence of companion animals in farms that did not co-graze cattle with other ruminants (AOR=10, 95%CI=1.2-95.9), Campylobacter positivity in chicken (AOR=5.8, 95%CI=2.2-16.2), presence of donkey (AOR=5.0, 95%CI=1.1-27.4), presence of pigs (AOR=4.9, 95%CI=1.2-23.5), and minimal hygiene of the housing unit (AOR=3.3, 95%CI=0.9-12.6) were associated with Campylobacter carriage in cattle. Keeping chicken and other birds irrespective of their Campylobacter status appeared to have a "protective" effect (AOR=0.2, 95%CI=0.03-0.6), against Campylobacter positivity in cattle. This suggests a complex web of transmission pathways of campylobacters in cattle and the environment. Interventions targeting these factors coupled with stringent biosecurity and sanitary measures are recommended so as to minimize the risk of Campylobacter transmission and/or occurrence in cattle environment.
Campylobacter organisms are the major cause of bacterial gastroenteritis and diarrhoeal illness i... more Campylobacter organisms are the major cause of bacterial gastroenteritis and diarrhoeal illness in man and livestock. Campylobacter is growingly becoming resistant to critically crucial antibiotics; thereby presenting public health challenge. Tis study aimed at establishing antimicrobial use, susceptibility profiles, and resistance genes in Campylobacter isolates recovered from chicken, cattle, and cattle-trough water samples. The study was conducted between October 2020 and May 2022 and involved the revival of cryopreserved Campylobacter isolates confirmed by PCR from a previous prevalence study in Kajiado County, Kenya. Data on antimicrobial use and animal health-seeking behaviour among livestock owners (from the same farms where sampling was done for the prevalence study) were collected through interview using a pretested semi structured questionnaire. One hundred and three isolates (29 C. coli (16 cattle isolates, 9 chicken isolates, and 4 water isolates) and 74 C. jejuni (38 cattle isolates, 30chicken isolates, and 6 water isolates)) were assayed for phenotypic antibiotic susceptibility profile using the Kirby–Bauer disk diffusion method for ampicillin (AX), tetracycline (TE), gentamicin (GEN), erythromycin (E), ciprofloxacin (CIP), and nalidixic acid (NA). Furthermore, detection of genes conferring resistance to tetracyclines (tet (O), β-lactams (blaOXA-61 ), aminoglycosides(aph-3-1), (fluoro)quinolones (gyrA), and multidrug efflux pump (cmeB) encoding resistance to multiple antibiotics was detected by mPCR and confirmed by DNA sequencing. The correlation between antibiotic use and resistance phenotypes was determined using the Pearson’s correlation coefficient (r) method. Tetracyclines, aminoglycosides, and β-lactam-based antibiotics were the most commonly used antimicrobials; with most farms generally reported using antimicrobials in chicken production systems than in cattle. The highest resistance amongst isolates was recorded in ampicillin (100%), followed by tetracycline (97.1%), erythromycin (75.7%), and ciprofloxacin (63.1%). Multidrug resistance (MDR) profile was observed in 99 of 103 (96.1%) isolates; with all the Campylobacter coli isolates displaying MDR. All chicken isolates (39/39, 100%) exhibited multidrug resistance. The AX-TE-E-CIP was the most common MDR pattern at 29.1%. The antibiotic resistance genes were detected as follows: tet (O), gyrA, cmeB, bla OXA-61, and aph-3-1 genes were detected at 93.2%, 61.2%, 54.4%, 36.9%, and 22.3% of all Campylobacter isolates, respectively. The highest correlations were found between tet (O) and tetracycline-resistant phenotypes for C. coli (96.4%) and C. jejuni(95.8%). A moderate level of concordance was observed between the Kirby–Bauer disk diffusion method (phenotypic assay) and PCR (genotypic assay) for tetracycline in both C. coli (kappa coefficient = 0.65) and C. jejuni (kappa coefficient = 0.55). The study discloses relatively high resistance profiles and multidrug resistance to antibiotics of critical importance in humans. The evolution of the multidrug-resistant Campylobacter isolates has been linked to the use and misuse of antimicrobials. Tis poses a potential hazard to public and animal health, necessitating need to reduce the use of antibiotics in livestock husbandry practice coupled with stringent biosecurity measures to mitigate antimicrobial resistance
ermophilic Campylobacter species are a leading cause of human gastroenteritis throughout the worl... more ermophilic Campylobacter species are a leading cause of human gastroenteritis throughout the world and have been implicated in reproductive disorders (abortion), mastitis, enteritis, and/or diarrhoea in livestock. A cross-sectional survey was conducted in Kajiado County to determine prevalence, seasonality, and molecular detection of thermophilic Campylobacter species (with emphasis on C. jejuni, C. coli, and other thermophilic Campylobacter species) in chicken, cattle, and respective pooled drinking water. A total of 457 samples comprising 265 cattle rectal swabs, 142 chicken cloacal swabs, and 50 trough water samples were collected from 55 randomly selected smallholder farms. Individual samples were subjected to standard techniques for isolation and biochemical tests, followed by singleplex polymerase chain reaction (sPCR) assays for identi cation and con rmation of genus and species. Overall, thermophilic Campylobacter prevalence was 35.4% (95% con dence interval (95% CI) 31.0-39.8), with C. jejuni dominating at 55.6% (95% CI 47.9-63.3%) over C. coli in all sample types. e highest thermophilic Campylobacter prevalence was observed in cloacal swabs of live chicken at 44.4% (95% CI 36.2-52.6%), followed by rectal swabs from live cattle at 30.9% (95% CI 25.3-36.5%). Water samples from cattle drinkers/trough were found to be contaminated at 34% (95% CI 20.9-47.1%). e isolation rate was higher in cattle under the con nement system (44.3%) (95% CI 36.1-52.5%) than in those under the free-roaming grazing system. ermophilic Campylobacter species were isolated in both seasons, with higher prevalence (39.8% (95% CI 33.6-45.9)) recorded during rainy and cold season in all sample types except for water. ere was signi cant (P < 0.05) association between season and thermophilic Campylobacter occurrence, even though there were no statistical di erences in the prevalence values across the two seasons. Results of this study demonstrate that cattle, chicken, and respective drinking water harbour potentially pathogenic thermophilic campylobacters, with C. jejuni being widely distributed among farms. It is possible that seasonal variations and cattle con nement result in di erences in thermophilic Campylobacter carriage. Further epidemiological and phylogenetic studies comparing distribution of thermophilic Campylobacter spp. isolates in livestock, environmental, and human samples are recommended to establish source attribution to reduce the impact of resultant diseases for the wellbeing of public and livestock.
Parasitic infestation in fish can lead to severe retarded growth and may be accompanied by mortal... more Parasitic infestation in fish can lead to severe retarded growth and may be accompanied by mortalities. Importantly, the quality of water in the holding facility may influence the parasitic biota. Therefore, a cross-sectional study was carried out from December 2017 to April 2018 in Kirinyaga County, Kenya, to determine the prevalence, intensity and the relationship between physico-chemical parameters of water and farmed fish parasites. A total of 294 live fish (Oreochromis niloticus, Clarias gariepinus, Carassius auratus and Cyprinus carpio carpio) were purchased from 22 randomly selected fish farms within the county. Physico-chemical parameters of water in 31 ponds were assessed in situ and ex situ, following standard procedures. Sampled fish were dissected immediately and subjected to parasitological examination by visual observation and light microscopy. The overall prevalence of parasitic infestation of the fish examined was 26.5% (78/294); with the highest infestation recorded in Nile tilapia (73.1%; 57/78). Eight parasite genera were recovered, with Diplostomum and Acanthocephalus species dominating each at 6.5% (19/294). The highest mean intensity was observed in Neascus spp. at 190 with an abundance range of 4-596 parasites. Mean physicochemical parameters of water were: pH (7.4), dissolved oxygen (5.9mgl-1), water temperature (25.3°C), phosphates (1.1mgl-1), nitrites (0.3mgl-1), nitrates (29.3mgl -1) and ammonia free nitrogen (0.8mgl-1). The water temperature and dissolved oxygen were below the optimal limit, while pH, ammonia, nitrites and phosphates levels in some ponds were above the desired limit for fish farming. Parasitic prevalence was positively correlated with ammonia free nitrogen, nitrates and phosphates, while there was a significant correlation between dissolved oxygen and abundance of the digenean trematode, Clinostomum cutaneum. These findings show that farmed fish harbour several parasite genera which may be influenced by physico-chemical characteristics of pond water. Fish farmers are advised to regularly monitor pond water quality in order to minimize fish stress and parasitic infestations; thus improving aquaculture productivity. Further long-term studies are recommended to determine the effect of water quality on parasitic fauna of farmed fish.
Nile tilapia (Oreochromis niloticus) is the most cultured and available fish for Kenyan consumers... more Nile tilapia (Oreochromis niloticus) is the most cultured and available fish for Kenyan consumers, and therefore, any tilapine disease deprives them the valuable source of protein. Nile tilapia farm was diagnosed with severe concurrent black spot disease and multiple bacteriosis using gross lesions and parasitological, histopathology, and standard bacteriological procedures. A total of 25 fish were sampled and inspected, and all of them had raised, macroscopic 1 mm-sized black spot lesions.)e mean intensity of black spots per fish was 728 with an abundance of 2-1740 metacercariae cysts per fish. A high intensity of black spot infestation was observed in the fins (43.9%), skin and underlying muscles (18.3%), and gills (18%). In addition, histopathological data confirmed presence of a metacercaria of Neascus spp. as the aetiological agent of black spot disease. Furthermore, a thick fibrous capsule around the metacercaria, black pigment melanomacrophages, and moderate muscle atrophy were observed.)e most prevalent bacteria isolated were Aeromonas, Enterobacter cloacae, Klebsiella pneumoniae, and Micrococcus luteus. Physicochemical parameters of pond water were temperature (28.2°C), dissolved oxygen (4.2 mgl −1), pH (8.5), ammonia free nitrogen (15.8 mgl −1), alkalinity (112 mgl −1), hardness (68 mgl −1), nitrites (0.058 mgl −1), nitrates (58 mgl −1), and phosphates (0.046 mgl −1). However, the levels of nitrates, nitrites, alkalinity, and ammonia free nitrogen exceeded the recommended limits. In conclusion, these findings suggest that coinfections by these organisms coupled by water quality-related stress can be associated with lowgrade mortality observed in postfingerling tilapia as well as reduced growth.)e authors recommended immediate destocking, thorough disinfection, and control of piscivorous birds. Moreover, attention ought to be geared towards prevention of parasitic infestations in fish so as to minimize fish deaths related to secondary bacteriosis. Further experimental studies should be carried out to elucidate the relationship of these pathogens.
Fish bacterial pathogens cause diseases which result in a considerable economic impact on the aqu... more Fish bacterial pathogens cause diseases which result in a considerable economic impact on the aquaculture industry, necessitating the use of antimicrobials for their control. However, intensive and indiscriminate use of antimicrobials has led to increased occurrence of drug resistance in pathogenic bacteria, as well as normal flora.)e aim of the current study was to determine the susceptibility patterns of bacteria isolated from fish, with respect to some commonly used antibiotics and disinfectants. Bacteria were isolated between December 2017 and April 2018 from farmed Nile tilapia, African catfish, goldfish, and koi carp in Kirinyaga County, Kenya. Antibiotic and disinfectant susceptibility patterns of 48 isolates belonging to the genera Aeromonas, Proteus, Klebsiella, Citrobacter, Salmonella, Streptococcus, Pseudomonas, Escherichia, Serratia, and Micrococcus were established using the Kirby-Bauer disc diffusion method and agar well diffusion technique, respectively.)e antibiotics evaluated included ampicillin, tetracycline, co-trimoxazole, streptomycin, kanamycin, gentamicin, co-trimoxazole, and chloramphenicol, while the disinfectants tested were quaternary ammonium compound, formalin, hydrogen peroxide, sodium hypochlorite, and iodine. All the bacteria except Micrococcus, Escherichia, and Salmonella species showed multiple drug resistance patterns. Streptococcus showed resistance to six antibiotics, while Proteus, Pseudomonas, and Serratia were resistant to five antibiotics.)e multiple antibiotic resistance index ranged from 0.1 to 0.8, with Streptococcus spp. having the highest score value. All the organisms were sensitive to gentamicin, while co-trimoxazole and ampicillin showed the highest resistance at 73% (n � 34) and 62% (n � 31), respectively. Most of the disinfectants showed antibacterial activity with varying magnitudes.)e isolates were 100% sensitive to hydrogen peroxide and formalin, but were resistant to sodium hypochlorite at recommended user-dilution.)e study has shown that some of the bacterial isolates were resistant to common antibiotics and disinfectants; thus, it is recommended to include an antibiogram whenever making any therapeutic decision.)e resistant bacteria may transmit resistance genes to other fish bacteria and also to human bacteria, thus making it difficult to treat the resultant disease(s); thus, there is a possibility that these resistant bacteria may be transmitted to humans who consume or handle the carrier fish. It is, therefore, advisable that fish are cooked properly before consumption, so as to kill bacteria that may be present.
Fish mortality has an enormous impact on the aquaculture industry by reducing fish production and... more Fish mortality has an enormous impact on the aquaculture industry by reducing fish production and slowing industrial growth. A cross-sectional study was carried out in Kirinyaga County, Central Kenya, to evaluate potential risks of fish mortality and disease transmission and suitability of pond water for rearing fish. A semistructured questionnaire that focused on general information, management practices, and disease history was administered to 92 small-scale fish farmers. Parasitological examination of fish sampled from selected farms (farms that were reporting mortality at the time of sampling) was done by following the standard procedure. Water quality parameters for 33 ponds were evaluated in situ (recorded on pond site) and ex situ (analysed at the laboratory) following the standard methods. *e risks were assessed by adjusted odds ratio based on univariate regression analysis. Prevalent fish husbandry practices that were found to be associated with fish mortality and acquisition of pathogens in the study area were the use of raw livestock manure (0R � 1.500), high fish stocking density (0R � 1.168), and feeding fish on homemade rations (0R � 1.128). Parasitological investigation found infestation with Diplostomum spp., Dactylogyrus spp., Clinostomum spp., and Piscicola leeches. Water temperature and pH were found fit for rearing fish. Of the 33 fishpond water samples tested, 1 (3%) and 6 (18%) exceeded the recommended limits of <100 mg/L and <0.2 mg/L of nitrate and nitrite, respectively. Of the 29 fishpond water tested, 15 (59%) exceeded the recommended limits of <100 mg/L of total ammonia. *e findings show that the use of raw livestock manure, high fish stocking density, high nitrates and nitrites, and high ammonia levels in fishponds are potential risk factors for fish mortality and acquisition of infectious pathogens in a pond environment in a rural setup, in Central Kenya. *ere is a need to address the above factors in small-scale farming practices to minimize fish loss and also to prevent the occurrence and spread of infectious pathogens.
International Journal of Fisheries and Aquatic Studies, 2019
Bacterial infections cause low to high mortality in fish, affecting the productivity of aquacultu... more Bacterial infections cause low to high mortality in fish, affecting the productivity of aquaculture. This study aimed at determining the occurrence of bacterial pathogens in farmed tilapia, catfish, goldfish and koi carp and source pond water in Kirinyaga County. A total of 181 healthy-appearing fish and 27 water samples from randomly selected fish farms in the county were processed. Bacteriological isolation was done on aseptically collected skin and kidney swabs; gills and a portion of intestines from each fish and water samples. Isolated bacteria were identified by colony morphology, Gram stain and biochemical characteristics, and some further characterized using API-20E kit. A total of 329 bacterial isolates were recovered from fish organs and 39 from pond water samples. They belonged to 17 genera with 18 different identified bacterial species. The most prevalent species found on the skin, gills, intestines, kidney, and water samples belonged to five genera: Proteus spp. (14.9%), Aeromonas hydrophila (8.2%), Aeromonas caviae (6.3%), Plesiomonas (5.2%), Flavobacterium spp. (5.2%), Aeromonas sobria (4.3%) and Micrococcus spp. (4.3%). Some isolates (11%, n=42) could not be identified. Bacterial species recovered from fish samples were also found in the water samples except: Streptococcus spp., Pseudomonas luteola, Serratia plymuthica and Klebsiella oxytoca. Raoultella terrigena was recovered from water samples only. The study has shown that farmed fish and aquatic environments harbor potentially pathogenic and zoonotic bacteria which may cause significant fish diseases and public health risks. Therefore, there is need to implement stringent management and biosecurity programs.
Thermotolerant campylobacters are genetically diverse species; associated with septic abortion in... more Thermotolerant campylobacters are genetically diverse species; associated with septic abortion in cattle, sheep and goats; and bovine mastitis with the most important being Campylobacter jejuni [1]. Campylobacters also poses a significant public health burden, which ultimately result in major costs to the health care system and economic impacts due to lost productivity. Infected poultry are considered the main reservoirs for transferring campylobacters to other farm animals and man. The epidemiology (transmission dynamics regarding what sources, how, and where) of campylobacters in cattle and poultry are poorly comprehended (especially in arid and semi-arid areas including Kajiado County), and has not been fully characterized probably due to ubiquitous and fastidious nature of the organism; as most studies have been carried out at abattoir level. While probable route of transmission in livestock (poultry and cattle) is from contaminated environmental sources (pasture and water) and chicken sources; there’s need to examine the potential role of seasonality and climatic factors. The present study aimed to investigate associations between occurrence of thermotolerant campylobacters in cattle, chicken, water and factors related to climate in Kajiado County
Proceedings of 52nd Kenya Veterinary Association Annual Scientific Conference, 2018
Black spot disease is common in freshwater fish and is usually caused by metacercariae of a digen... more Black spot disease is common in freshwater fish and is usually caused by metacercariae of a digenean trematode, Neascus spp. in the Diplostomidae family. This disease was first encountered in December 2017 in a grow-out Oreochromis niloticus (tilapia) farm with a single liner pond in Kirinyaga Central sub-county, Kirinyaga County. Two (2) mm sized black spots were found in various organs of 10 sampled fish on parasitological examination. However, in a neighbouring farm (<1km away), tilapia in a liner pond were negative for this condition. Risk factors of the disease were assessed through semi-structured questionnaire interview and researchers’ observations of the pond and its environs. A resampling of the farm was conducted in January 2018, where 45 tilapia were collected to determine distribution and intensity of lesions. The black spots from diseased fish were counted on the left side of the fish and multiplied by 2 to determine the intensity. All the sampled tilapia had black spots lesions and percentage distribution in various organs was as follows; fins (43.9%), skin and muscles (23.9%), operculum (8.8%), eyes (2.8%), inside the mouth (2.6%) and gills (1.8%). A mean intensity of 728was recorded and females had higher intensity compared to male fish (p<0.05). Correlation between condition factor and intensity was not statistically significant (p>0.05). Among the risk factors of the disease noted within the farm were presence of snails and piscivorous birds which propagate the life cycle of the parasites. Vegetation such as banana stems which were very close to the ponds were noted to be hiding places for these snails. The dam-liner and the poorly constructed dykes were pervious and this could also pose a risk especially during the rainy season. Black spot disease has an indirect implication on the economic value of fish as those infested are rejected at market level due to aesthetic reasons leading to economic losses. Recommended control measures include use of cover nets over the ponds to prevent interaction of predatory birds which are definitive hosts of digenean trematodes of fish and farming crops such as bananas which harbour snail intermediate hosts in close proximity to fish ponds should be discouraged. Key words: Black spot disease, Neascus spp., metacercariae, predator birds
Globally, parasitic infections hinder aquaculture productivity and sustainability. Improper water... more Globally, parasitic infections hinder aquaculture productivity and sustainability. Improper water quality parameters reduce fish immunity, make them susceptible to parasites, and enhance parasitic proliferation in culture systems. Subsequently, this study aimed to determine the prevalence and intensity of ecto-and endo-parasite infesting Oreochromis niloticus in varying water quality in aquaculture systems in Kericho, Bomet, and Nakuru counties. A total of 220 Oreochromis niloticus samples were captured from 11 liner ponds, eight earthen ponds, two concrete ponds, and one plastic tank from 22 farms in the three counties. External and internal organs were examined for parasite infestation. Skin scrapings and squash preparation of fish eyes were also examined to reveal the organisms through microscopic examination. A Pearson's correlation analysis between physicochemical parameters and parasitic prevalence was used to determine the strength and direction of correlation coefficients with significance at 95%. Overall parasitic prevalence infestation was 39.6% (87/220). Ten parasite genera were recovered, with Dactylogyrus species dominating overall at 15.9% (35/220), followed by Trichodina spp. (7.7%; 17/220). Epistylis species had the highest mean intensity of 12.8 AE 35.7 (total number of Epistylis parasites (141)/total of infested fish (11)). Earthen ponds had a significantly higher (36.2%, 29/80) prevalence of Dactylogyrus sp. than liner ponds (3.6%, 4/110) (p<0:001). Dissolved oxygen levels were 16.9 AE 0.7 mgL −1 in Bomet, 14.9 AE 0.3 mgL −1 in Kericho, and 12.5 AE 0.5 mgL −1 in Nakuru which were above desirable range for fish culture. The electrical conductivity in Bomet was 76 AE 5 µS/cm and Kericho 52 AE 4 µS/cm below the desirable range. Temperature, pH, phosphate, nitrates, and nitrites were within the desirable limit for fish farming. Electrical conductivity and pH had positive correlation of 1 and 0.97, respectively, with the prevalence of Acanthocephalus, Euclinostomum, and Trichodina species. Temperature and nitrate positively correlated between 0.80-0.89 and 0.90-0.99, respectively, with the prevalence of Dactylogyrus, Riboscyphidia, Epistylis, Camallanus, and Paracamallanus species. The study demonstrates that water quality significantly influences parasitic prevalence in aquaculture systems. Therefore, it is crucial for farmers to monitor water quality parameters to mitigate parasitic infestations.
Globally, parasitic infections hinder aquaculture productivity and sustainability. Improper water... more Globally, parasitic infections hinder aquaculture productivity and sustainability. Improper water quality parameters reduce fish immunity, make them susceptible to parasites, and enhance parasitic proliferation in culture systems. Subsequently, this study aimed to determine the prevalence and intensity of ecto-and endo-parasite infesting Oreochromis niloticus in varying water quality in aquaculture systems in Kericho, Bomet, and Nakuru counties. A total of 220 Oreochromis niloticus samples were captured from 11 liner ponds, eight earthen ponds, two concrete ponds, and one plastic tank from 22 farms in the three counties. External and internal organs were examined for parasite infestation. Skin scrapings and squash preparation of fish eyes were also examined to reveal the organisms through microscopic examination. A Pearson's correlation analysis between physicochemical parameters and parasitic prevalence was used to determine the strength and direction of correlation coefficients with significance at 95%. Overall parasitic prevalence infestation was 39.6% (87/220). Ten parasite genera were recovered, with Dactylogyrus species dominating overall at 15.9% (35/220), followed by Trichodina spp. (7.7%; 17/220). Epistylis species had the highest mean intensity of 12.8 AE 35.7 (total number of Epistylis parasites (141)/total of infested fish (11)). Earthen ponds had a significantly higher (36.2%, 29/80) prevalence of Dactylogyrus sp. than liner ponds (3.6%, 4/110) (p<0:001). Dissolved oxygen levels were 16.9 AE 0.7 mgL −1 in Bomet, 14.9 AE 0.3 mgL −1 in Kericho, and 12.5 AE 0.5 mgL −1 in Nakuru which were above desirable range for fish culture. The electrical conductivity in Bomet was 76 AE 5 µS/cm and Kericho 52 AE 4 µS/cm below the desirable range. Temperature, pH, phosphate, nitrates, and nitrites were within the desirable limit for fish farming. Electrical conductivity and pH had positive correlation of 1 and 0.97, respectively, with the prevalence of Acanthocephalus, Euclinostomum, and Trichodina species. Temperature and nitrate positively correlated between 0.80-0.89 and 0.90-0.99, respectively, with the prevalence of Dactylogyrus, Riboscyphidia, Epistylis, Camallanus, and Paracamallanus species. The study demonstrates that water quality significantly influences parasitic prevalence in aquaculture systems. Therefore, it is crucial for farmers to monitor water quality parameters to mitigate parasitic infestations.
Campylobacter is a zoonotic foodborne pathogen that is often linked with gastroenteritis and othe... more Campylobacter is a zoonotic foodborne pathogen that is often linked with gastroenteritis and other extraintestinal infections in humans. This study is aimed at determining the genetic determinants of virulence-encoding genes responsible for flagellin motility protein A (flaA), Campylobacter adhesion to fibronectin F (cadF), Campylobacter invasion antigen B (ciaB) and cytolethal distending toxin (cdt) A (cdtA) in Campylobacter species. A total of 29 Campylobacter coli isolates (16 from cattle, 9from chicken, and 4 from water samples) and 74 Campylobacter jejuni isolates (38 from cattle, 30 from chicken, and 6 from water samples) described in an earlier study in Kajiado County, Kenya, were examined for the occurrence of virulence-associated genes using polymerase chain reaction (PCR) and amplicon sequencing. The correlations among virulence genes were analyzed using Pearson’s correlation coefficient (R) method. Among the 103 Campylobacter strains screened, 89 were found to harbour a single or multiple virulence gene(s), giving an overall prevalence of 86.4%. C. jejuni strains had the highest prevalence of multivirulence at 64.9% (48/74), compared to C. coli (58.6%, 17/29). The ciaB and flaA genes were the most common virulence genes detected in C. jejuni (81.1% [60/74] and 62.2% [46/74], respectively) and in C. coli (each at 62.1%;18/29). Campylobacter isolates from chicken harboured the most virulence-encoding genes. C. jejuni strains from chicken and cattle harboured the highest proportions of the cdtA and ciaB genes, respectively. All the C. coli strains from water samples harboured the cadF and flaA genes. The results obtained further revealed a significant positive correlation between cadF and flaA (R = 0 733). C. jejuni and C. coli strains from cattle, chicken, and water harbour virulence markers responsible for motility/colonization, invasion, adherence, and toxin production, evoking their important role in campylobacteriosis development among humans and livestock. The identification of cattle, chicken, and water samples as reservoirs of virulent Campylobacter spp. highlights the possible risk to human health. These data on some virulence genes of Campylobacter will assist food safety and public health officials in formulating policy statements. Keywords: Campylobacter; campylobacteriosis; foodborne; livestock; multiple virulence genes; public health; zoonotic
Management practices and risk factors associated with parasitic infestations in farmed Nile tilapia in Bomet and Kericho counties, Kenya, 2024
The aquaculture has surged in Kenya owing to dwindling wild stocks. However, this is coupled with... more The aquaculture has surged in Kenya owing to dwindling wild stocks. However, this is coupled with challenges such as limited fish health knowledge and biosecurity measures. A cross sectional study was undertaken to determine risk factors and management practices associated with parasitic infestation of farmed Nile tilapia in Bomet and Kericho counties, Kenya. A total of 150 Nile tilapia (Oreochromis niloticus) were collected and subjected to standard parasitological examination. Potential risk factors associated with parasitic infestation in fish were assessed in 88 farms using pretested semi-structured questionnaires and on-site farm visit observations. Logistic regression analysis with the estimation of odds ratios (OR) was used to assess potential risks factors. Tilapia were dominant fish (>95%) and were farmed mainly in earthen ponds (> 61%). Most farmers (52.3%) used river water for ponds and 14% had experienced floods that introduced predators in the ponds. Farmers relied on fisheries department harvesting nets and only 12.5% sun dried the nets after use. Few farmers (37.5%) frequently cleaned and dried ponds before restocking, while 34.1% did not remove the pond bottom soil after fish harvesting. Approximately 3.4% of the farmers rated diseases as the main obstacle in fish farming and, 68.2% could not identify sick fish. Those who identified sick fish reported abnormal swimming (23.9%) and mortality (8%). Out of the 150 fish sampled, 62 (prevalence = 42%) were found to be infected with different genera of parasites including: Dactylogyrus spp. (21%); Epistylis spp. (7.3%); Riboscyphidia spp. (6.7%); Trichodina spp. (6%); Paracamallanus spp. (4.7%); Camallanus spp. (2%); Diplostomum spp. (2%) and Contracaecum spp. (1.3%). Dactylogyrus spp. were common in earthen ponds (91%) (p<0.001). Some management practices identified as possible risk factors for parasitic infestation in fish included; pond fertilization using livestock manure (OR=5.633), siting fish ponds in valleys/gullies (OR=2.028), use of river water for aqua farming (OR=1.654) and earthen pond types (OR=2.023). Farmers and extension workers should be trained on the importance of fish health and biosecurity. The authors recommend further detailed longitudinal controlled studies which consider myriad fish husbandry practices with parasitic infestations.
International Journal of Fisheries and Aquatic Studies, 2024
Bacterial infections can cause latent, low to high mortalities in aquaculture farms and wild fish... more Bacterial infections can cause latent, low to high mortalities in aquaculture farms and wild fish while some bacteria may be zoonotic. This study isolated, characterized and identify potential pathogenic and zoonotic aerobic bacteria in farmed and wild Oreochromis jipe, O. niloticus, their hybrids and culture water source from Taita-Taveta County. One hundred and eleven apparently healthy-appearing fish consisting of 67 O. jipe, 34 O. niloticus and 10 hybrids and nine water (7 farms and 2 Lake Jipe) samples were processed. Samples were aseptically collected from each fish, namely, skin and kidney swabs; gills and intestinal tissues. Conventional culture, biochemical and Matrix Assisted Laser Desorption/Ionization Time of Flight Mass Spectrometry tests were done to identify isolated bacteria. A total of 596 bacterial isolates representing 22 genera were recovered from 444 fish organs and 9 water samples. Of these, the highest numbers were from the gills at 29.7% followed by skin 29.6%, intestines 24.4%, kidney 11.8% and the least from water at 4.7%. Potential fish pathogens were Bacillus cereus (8%), Aeromonas veronii (8%), Aeromonas hydrophila (5%), Lysinibacillus fusiformis (5%), Acinetobacter Johnsonii (4%) and Acinetobacter solii (4%). Potential pathogenic and zoonotic bacteria isolated were Staphylococcus lentus 17.9% (5/28), Aeromonas hydrophila 10.7% (3/28) and Aeromonas hormaechei 7.1% (2/28). From the sampling site; 28.4% (169/596) of the total isolates were collected from Taveta, then Mwatate with 26.9% (160/596), Mkwajuni 16.8%, (98/596), Kenya Wildlife Service 7.0% (42/596), Wundanyi 6.7% (40/596), Voi 6.6% (39/596) and the inlet of the Lake Jipe had a 3.2% (19/596) and from the water samples 4.7% (28/596). These findings confirm that fish in aquaculture farms, wild fish and water used for aquaculture harbors potentially pathogenic and zoonotic bacteria which may cause fish diseases and pose public health risks. Extension officers and farmers need awareness on mitigation measures against these pathogens.
International Journal of Fisheries and Aquatic Studies 2024; 12(4): 49-58, 2024
Bacterial infections can cause latent, low to high mortalities in aquaculture farms and wild fish... more Bacterial infections can cause latent, low to high mortalities in aquaculture farms and wild fish while some bacteria may be zoonotic. This study isolated, characterized and identify potential pathogenic and zoonotic aerobic bacteria in farmed and wild Oreochromis jipe, O. niloticus, their hybrids and culture water source from Taita-Taveta County. One hundred and eleven apparently healthy-appearing fish consisting of 67 O. jipe, 34 O. niloticus and 10 hybrids and nine water (7 farms and 2 Lake Jipe) samples were processed. Samples were aseptically collected from each fish, namely, skin and kidney swabs; gills and intestinal tissues. Conventional culture, biochemical and Matrix Assisted Laser Desorption/Ionization Time of Flight Mass Spectrometry tests were done to identify isolated bacteria. A total of 596 bacterial isolates representing 22 genera were recovered from 444 fish organs and 9 water samples. Of these, the highest numbers were from the gills at 29.7% followed by skin 29.6%, intestines 24.4%, kidney 11.8% and the least from water at 4.7%. Potential fish pathogens were Bacillus cereus (8%), Aeromonas veronii (8%), Aeromonas hydrophila (5%), Lysinibacillus fusiformis (5%), Acinetobacter Johnsonii (4%) and Acinetobacter solii (4%). Potential pathogenic and zoonotic bacteria isolated were Staphylococcus lentus 17.9% (5/28), Aeromonas hydrophila 10.7% (3/28) and Aeromonas hormaechei 7.1% (2/28). From the sampling site; 28.4% (169/596) of the total isolates were collected from Taveta, then Mwatate with 26.9% (160/596), Mkwajuni 16.8%, (98/596), Kenya Wildlife Service 7.0% (42/596), Wundanyi 6.7% (40/596), Voi 6.6% (39/596) and the inlet of the Lake Jipe had a 3.2% (19/596) and from the water samples 4.7% (28/596). These findings confirm that fish in aquaculture farms, wild fish and water used for aquaculture harbors potentially pathogenic and zoonotic bacteria which may cause fish diseases and pose public health risks. Extension officers and farmers need awareness on mitigation measures against these pathogens.
International Journal of Fisheries and Aquatic Studies , 2024
Bacterial infections can cause latent, low to high mortalities in aquaculture farms and wild fish... more Bacterial infections can cause latent, low to high mortalities in aquaculture farms and wild fish while some bacteria may be zoonotic. This study isolated, characterized and identify potential pathogenic and zoonotic aerobic bacteria in farmed and wild Oreochromis jipe, O. niloticus, their hybrids and culture water source from Taita-Taveta County. One hundred and eleven apparently healthy-appearing fish consisting of 67 O. jipe, 34 O. niloticus and 10 hybrids and nine water (7 farms and 2 Lake Jipe) samples were processed. Samples were aseptically collected from each fish, namely, skin and kidney swabs; gills and intestinal tissues. Conventional culture, biochemical and Matrix Assisted Laser Desorption/Ionization Time of Flight Mass Spectrometry tests were done to identify isolated bacteria. A total of 596 bacterial isolates representing 22 genera were recovered from 444 fish organs and 9 water samples. Of these, the highest numbers were from the gills at 29.7% followed by skin 29.6%, intestines 24.4%, kidney 11.8% and the least from water at 4.7%. Potential fish pathogens were Bacillus cereus (8%), Aeromonas veronii (8%), Aeromonas hydrophila (5%), Lysinibacillus fusiformis (5%), Acinetobacter Johnsonii (4%) and Acinetobacter solii (4%). Potential pathogenic and zoonotic bacteria isolated were Staphylococcus lentus 17.9% (5/28), Aeromonas hydrophila 10.7% (3/28) and Aeromonas hormaechei 7.1% (2/28). From the sampling site; 28.4% (169/596) of the total isolates were collected from Taveta, then Mwatate with 26.9% (160/596), Mkwajuni 16.8%, (98/596), Kenya Wildlife Service 7.0% (42/596), Wundanyi 6.7% (40/596), Voi 6.6% (39/596) and the inlet of the Lake Jipe had a 3.2% (19/596) and from the water samples 4.7% (28/596). These findings confirm that fish in aquaculture farms, wild fish and water used for aquaculture harbors potentially pathogenic and zoonotic bacteria which may cause fish diseases and pose public health risks. Extension officers and farmers need awareness on mitigation measures against these pathogens. Keywords: Aeromonas hydrophila, aquaculture, fish pathogens, prevalence, wild fish, Zoonosis
International Journal of Fisheries and Aquatic Studies, 2024
The aquaculture has surged in Kenya owing to dwindling wild stocks. However, this is coupled with... more The aquaculture has surged in Kenya owing to dwindling wild stocks. However, this is coupled with challenges such as limited fish health knowledge and biosecurity measures. A cross sectional study was undertaken to determine risk factors and management practices associated with parasitic infestation of farmed Nile tilapia in Bomet and Kericho counties, Kenya. A total of 150 Nile tilapia (Oreochromis niloticus) were collected and subjected to standard parasitological examination. Potential risk factors associated with parasitic infestation in fish were assessed in 88 farms using pretested semi-structured questionnaires and on-site farm visit observations. Logistic regression analysis with the estimation of odds ratios (OR) was used to assess potential risks factors. Tilapia were dominant fish (>95%) and were farmed mainly in earthen ponds (> 61%). Most farmers (52.3%) used river water for ponds and 14% had experienced floods that introduced predators in the ponds. Farmers relied on fisheries department harvesting nets and only 12.5% sun dried the nets after use. Few farmers (37.5%) frequently cleaned and dried ponds before restocking, while 34.1% did not remove the pond bottom soil after fish harvesting. Approximately 3.4% of the farmers rated diseases as the main obstacle in fish farming and, 68.2% could not identify sick fish. Those who identified sick fish reported abnormal swimming (23.9%) and mortality (8%). Out of the 150 fish sampled, 62 (prevalence = 42%) were found to be infected with different genera of parasites including: Dactylogyrus spp. (21%); Epistylis spp. (7.3%); Riboscyphidia spp. (6.7%); Trichodina spp. (6%); Paracamallanus spp. (4.7%); Camallanus spp. (2%); Diplostomum spp. (2%) and Contracaecum spp. (1.3%). Dactylogyrus spp. were common in earthen ponds (91%) (p<0.001). Some management practices identified as possible risk factors for parasitic infestation in fish included; pond fertilization using livestock manure (OR=5.633), siting fish ponds in valleys/gullies (OR=2.028), use of river water for aqua farming (OR=1.654) and earthen pond types (OR=2.023). Farmers and extension workers should be trained on the importance of fish health and biosecurity. The authors recommend further detailed longitudinal controlled studies which consider myriad fish husbandry practices with parasitic infestations. Keywords: Biosecurity, fish health, management practices, nile tilapia
Integrated farms are smallholder farms that rear a mixture of different food animals in close pro... more Integrated farms are smallholder farms that rear a mixture of different food animals in close proximity. Subsequently, a survey was carried out to establish two aspects: (1) occurrence rate of thermophilic Campylobacter in cattle in 55 integrated small-scale farms within Kajiado County; a total of 265 cattle rectal swabs were randomly collected for bacterial isolation, and (2) factors associated with Campylobacter occurrence; these included administration of pre-tested questionnaires, to collect data on respective farm characteristics and management practices, and isolation of Campylobacter from respective water and chicken cloacal swabs (as possible sources of infection). The collected rectal/cloacal swabs and water samples were specifically processed for Campylobacter isolation, followed by confirmation using a singleplex polymerase chain reaction (PCR) assay, while the questionnaire data was analyzed using logistic regression models. Campylobacters in cattle were detected in 72.7% (95% confidence interval (95%CI) =60.9-84.5) of the surveyed farms. The farm/herd level Campylobacter positivity ranged from 12.5% to 100%; 27.3% (95%CI=15.5-39.1) of the surveyed farms were Campylobacter negative. Of the Campylobacter positive farms, the mean prevalence was 48.14%, with a median of 50%. Farm stocking dairy breeds [adjusted odds ratio (AOR)=12.7, 95%CI: 3.2-60], presence of companion animals in farms that did not co-graze cattle with other ruminants (AOR=10, 95%CI=1.2-95.9), Campylobacter positivity in chicken (AOR=5.8, 95%CI=2.2-16.2), presence of donkey (AOR=5.0, 95%CI=1.1-27.4), presence of pigs (AOR=4.9, 95%CI=1.2-23.5), and minimal hygiene of the housing unit (AOR=3.3, 95%CI=0.9-12.6) were associated with Campylobacter carriage in cattle. Keeping chicken and other birds irrespective of their Campylobacter status appeared to have a "protective" effect (AOR=0.2, 95%CI=0.03-0.6), against Campylobacter positivity in cattle. This suggests a complex web of transmission pathways of campylobacters in cattle and the environment. Interventions targeting these factors coupled with stringent biosecurity and sanitary measures are recommended so as to minimize the risk of Campylobacter transmission and/or occurrence in cattle environment.
Campylobacter organisms are the major cause of bacterial gastroenteritis and diarrhoeal illness i... more Campylobacter organisms are the major cause of bacterial gastroenteritis and diarrhoeal illness in man and livestock. Campylobacter is growingly becoming resistant to critically crucial antibiotics; thereby presenting public health challenge. Tis study aimed at establishing antimicrobial use, susceptibility profiles, and resistance genes in Campylobacter isolates recovered from chicken, cattle, and cattle-trough water samples. The study was conducted between October 2020 and May 2022 and involved the revival of cryopreserved Campylobacter isolates confirmed by PCR from a previous prevalence study in Kajiado County, Kenya. Data on antimicrobial use and animal health-seeking behaviour among livestock owners (from the same farms where sampling was done for the prevalence study) were collected through interview using a pretested semi structured questionnaire. One hundred and three isolates (29 C. coli (16 cattle isolates, 9 chicken isolates, and 4 water isolates) and 74 C. jejuni (38 cattle isolates, 30chicken isolates, and 6 water isolates)) were assayed for phenotypic antibiotic susceptibility profile using the Kirby–Bauer disk diffusion method for ampicillin (AX), tetracycline (TE), gentamicin (GEN), erythromycin (E), ciprofloxacin (CIP), and nalidixic acid (NA). Furthermore, detection of genes conferring resistance to tetracyclines (tet (O), β-lactams (blaOXA-61 ), aminoglycosides(aph-3-1), (fluoro)quinolones (gyrA), and multidrug efflux pump (cmeB) encoding resistance to multiple antibiotics was detected by mPCR and confirmed by DNA sequencing. The correlation between antibiotic use and resistance phenotypes was determined using the Pearson’s correlation coefficient (r) method. Tetracyclines, aminoglycosides, and β-lactam-based antibiotics were the most commonly used antimicrobials; with most farms generally reported using antimicrobials in chicken production systems than in cattle. The highest resistance amongst isolates was recorded in ampicillin (100%), followed by tetracycline (97.1%), erythromycin (75.7%), and ciprofloxacin (63.1%). Multidrug resistance (MDR) profile was observed in 99 of 103 (96.1%) isolates; with all the Campylobacter coli isolates displaying MDR. All chicken isolates (39/39, 100%) exhibited multidrug resistance. The AX-TE-E-CIP was the most common MDR pattern at 29.1%. The antibiotic resistance genes were detected as follows: tet (O), gyrA, cmeB, bla OXA-61, and aph-3-1 genes were detected at 93.2%, 61.2%, 54.4%, 36.9%, and 22.3% of all Campylobacter isolates, respectively. The highest correlations were found between tet (O) and tetracycline-resistant phenotypes for C. coli (96.4%) and C. jejuni(95.8%). A moderate level of concordance was observed between the Kirby–Bauer disk diffusion method (phenotypic assay) and PCR (genotypic assay) for tetracycline in both C. coli (kappa coefficient = 0.65) and C. jejuni (kappa coefficient = 0.55). The study discloses relatively high resistance profiles and multidrug resistance to antibiotics of critical importance in humans. The evolution of the multidrug-resistant Campylobacter isolates has been linked to the use and misuse of antimicrobials. Tis poses a potential hazard to public and animal health, necessitating need to reduce the use of antibiotics in livestock husbandry practice coupled with stringent biosecurity measures to mitigate antimicrobial resistance
ermophilic Campylobacter species are a leading cause of human gastroenteritis throughout the worl... more ermophilic Campylobacter species are a leading cause of human gastroenteritis throughout the world and have been implicated in reproductive disorders (abortion), mastitis, enteritis, and/or diarrhoea in livestock. A cross-sectional survey was conducted in Kajiado County to determine prevalence, seasonality, and molecular detection of thermophilic Campylobacter species (with emphasis on C. jejuni, C. coli, and other thermophilic Campylobacter species) in chicken, cattle, and respective pooled drinking water. A total of 457 samples comprising 265 cattle rectal swabs, 142 chicken cloacal swabs, and 50 trough water samples were collected from 55 randomly selected smallholder farms. Individual samples were subjected to standard techniques for isolation and biochemical tests, followed by singleplex polymerase chain reaction (sPCR) assays for identi cation and con rmation of genus and species. Overall, thermophilic Campylobacter prevalence was 35.4% (95% con dence interval (95% CI) 31.0-39.8), with C. jejuni dominating at 55.6% (95% CI 47.9-63.3%) over C. coli in all sample types. e highest thermophilic Campylobacter prevalence was observed in cloacal swabs of live chicken at 44.4% (95% CI 36.2-52.6%), followed by rectal swabs from live cattle at 30.9% (95% CI 25.3-36.5%). Water samples from cattle drinkers/trough were found to be contaminated at 34% (95% CI 20.9-47.1%). e isolation rate was higher in cattle under the con nement system (44.3%) (95% CI 36.1-52.5%) than in those under the free-roaming grazing system. ermophilic Campylobacter species were isolated in both seasons, with higher prevalence (39.8% (95% CI 33.6-45.9)) recorded during rainy and cold season in all sample types except for water. ere was signi cant (P < 0.05) association between season and thermophilic Campylobacter occurrence, even though there were no statistical di erences in the prevalence values across the two seasons. Results of this study demonstrate that cattle, chicken, and respective drinking water harbour potentially pathogenic thermophilic campylobacters, with C. jejuni being widely distributed among farms. It is possible that seasonal variations and cattle con nement result in di erences in thermophilic Campylobacter carriage. Further epidemiological and phylogenetic studies comparing distribution of thermophilic Campylobacter spp. isolates in livestock, environmental, and human samples are recommended to establish source attribution to reduce the impact of resultant diseases for the wellbeing of public and livestock.
Parasitic infestation in fish can lead to severe retarded growth and may be accompanied by mortal... more Parasitic infestation in fish can lead to severe retarded growth and may be accompanied by mortalities. Importantly, the quality of water in the holding facility may influence the parasitic biota. Therefore, a cross-sectional study was carried out from December 2017 to April 2018 in Kirinyaga County, Kenya, to determine the prevalence, intensity and the relationship between physico-chemical parameters of water and farmed fish parasites. A total of 294 live fish (Oreochromis niloticus, Clarias gariepinus, Carassius auratus and Cyprinus carpio carpio) were purchased from 22 randomly selected fish farms within the county. Physico-chemical parameters of water in 31 ponds were assessed in situ and ex situ, following standard procedures. Sampled fish were dissected immediately and subjected to parasitological examination by visual observation and light microscopy. The overall prevalence of parasitic infestation of the fish examined was 26.5% (78/294); with the highest infestation recorded in Nile tilapia (73.1%; 57/78). Eight parasite genera were recovered, with Diplostomum and Acanthocephalus species dominating each at 6.5% (19/294). The highest mean intensity was observed in Neascus spp. at 190 with an abundance range of 4-596 parasites. Mean physicochemical parameters of water were: pH (7.4), dissolved oxygen (5.9mgl-1), water temperature (25.3°C), phosphates (1.1mgl-1), nitrites (0.3mgl-1), nitrates (29.3mgl -1) and ammonia free nitrogen (0.8mgl-1). The water temperature and dissolved oxygen were below the optimal limit, while pH, ammonia, nitrites and phosphates levels in some ponds were above the desired limit for fish farming. Parasitic prevalence was positively correlated with ammonia free nitrogen, nitrates and phosphates, while there was a significant correlation between dissolved oxygen and abundance of the digenean trematode, Clinostomum cutaneum. These findings show that farmed fish harbour several parasite genera which may be influenced by physico-chemical characteristics of pond water. Fish farmers are advised to regularly monitor pond water quality in order to minimize fish stress and parasitic infestations; thus improving aquaculture productivity. Further long-term studies are recommended to determine the effect of water quality on parasitic fauna of farmed fish.
Nile tilapia (Oreochromis niloticus) is the most cultured and available fish for Kenyan consumers... more Nile tilapia (Oreochromis niloticus) is the most cultured and available fish for Kenyan consumers, and therefore, any tilapine disease deprives them the valuable source of protein. Nile tilapia farm was diagnosed with severe concurrent black spot disease and multiple bacteriosis using gross lesions and parasitological, histopathology, and standard bacteriological procedures. A total of 25 fish were sampled and inspected, and all of them had raised, macroscopic 1 mm-sized black spot lesions.)e mean intensity of black spots per fish was 728 with an abundance of 2-1740 metacercariae cysts per fish. A high intensity of black spot infestation was observed in the fins (43.9%), skin and underlying muscles (18.3%), and gills (18%). In addition, histopathological data confirmed presence of a metacercaria of Neascus spp. as the aetiological agent of black spot disease. Furthermore, a thick fibrous capsule around the metacercaria, black pigment melanomacrophages, and moderate muscle atrophy were observed.)e most prevalent bacteria isolated were Aeromonas, Enterobacter cloacae, Klebsiella pneumoniae, and Micrococcus luteus. Physicochemical parameters of pond water were temperature (28.2°C), dissolved oxygen (4.2 mgl −1), pH (8.5), ammonia free nitrogen (15.8 mgl −1), alkalinity (112 mgl −1), hardness (68 mgl −1), nitrites (0.058 mgl −1), nitrates (58 mgl −1), and phosphates (0.046 mgl −1). However, the levels of nitrates, nitrites, alkalinity, and ammonia free nitrogen exceeded the recommended limits. In conclusion, these findings suggest that coinfections by these organisms coupled by water quality-related stress can be associated with lowgrade mortality observed in postfingerling tilapia as well as reduced growth.)e authors recommended immediate destocking, thorough disinfection, and control of piscivorous birds. Moreover, attention ought to be geared towards prevention of parasitic infestations in fish so as to minimize fish deaths related to secondary bacteriosis. Further experimental studies should be carried out to elucidate the relationship of these pathogens.
Fish bacterial pathogens cause diseases which result in a considerable economic impact on the aqu... more Fish bacterial pathogens cause diseases which result in a considerable economic impact on the aquaculture industry, necessitating the use of antimicrobials for their control. However, intensive and indiscriminate use of antimicrobials has led to increased occurrence of drug resistance in pathogenic bacteria, as well as normal flora.)e aim of the current study was to determine the susceptibility patterns of bacteria isolated from fish, with respect to some commonly used antibiotics and disinfectants. Bacteria were isolated between December 2017 and April 2018 from farmed Nile tilapia, African catfish, goldfish, and koi carp in Kirinyaga County, Kenya. Antibiotic and disinfectant susceptibility patterns of 48 isolates belonging to the genera Aeromonas, Proteus, Klebsiella, Citrobacter, Salmonella, Streptococcus, Pseudomonas, Escherichia, Serratia, and Micrococcus were established using the Kirby-Bauer disc diffusion method and agar well diffusion technique, respectively.)e antibiotics evaluated included ampicillin, tetracycline, co-trimoxazole, streptomycin, kanamycin, gentamicin, co-trimoxazole, and chloramphenicol, while the disinfectants tested were quaternary ammonium compound, formalin, hydrogen peroxide, sodium hypochlorite, and iodine. All the bacteria except Micrococcus, Escherichia, and Salmonella species showed multiple drug resistance patterns. Streptococcus showed resistance to six antibiotics, while Proteus, Pseudomonas, and Serratia were resistant to five antibiotics.)e multiple antibiotic resistance index ranged from 0.1 to 0.8, with Streptococcus spp. having the highest score value. All the organisms were sensitive to gentamicin, while co-trimoxazole and ampicillin showed the highest resistance at 73% (n � 34) and 62% (n � 31), respectively. Most of the disinfectants showed antibacterial activity with varying magnitudes.)e isolates were 100% sensitive to hydrogen peroxide and formalin, but were resistant to sodium hypochlorite at recommended user-dilution.)e study has shown that some of the bacterial isolates were resistant to common antibiotics and disinfectants; thus, it is recommended to include an antibiogram whenever making any therapeutic decision.)e resistant bacteria may transmit resistance genes to other fish bacteria and also to human bacteria, thus making it difficult to treat the resultant disease(s); thus, there is a possibility that these resistant bacteria may be transmitted to humans who consume or handle the carrier fish. It is, therefore, advisable that fish are cooked properly before consumption, so as to kill bacteria that may be present.
Fish mortality has an enormous impact on the aquaculture industry by reducing fish production and... more Fish mortality has an enormous impact on the aquaculture industry by reducing fish production and slowing industrial growth. A cross-sectional study was carried out in Kirinyaga County, Central Kenya, to evaluate potential risks of fish mortality and disease transmission and suitability of pond water for rearing fish. A semistructured questionnaire that focused on general information, management practices, and disease history was administered to 92 small-scale fish farmers. Parasitological examination of fish sampled from selected farms (farms that were reporting mortality at the time of sampling) was done by following the standard procedure. Water quality parameters for 33 ponds were evaluated in situ (recorded on pond site) and ex situ (analysed at the laboratory) following the standard methods. *e risks were assessed by adjusted odds ratio based on univariate regression analysis. Prevalent fish husbandry practices that were found to be associated with fish mortality and acquisition of pathogens in the study area were the use of raw livestock manure (0R � 1.500), high fish stocking density (0R � 1.168), and feeding fish on homemade rations (0R � 1.128). Parasitological investigation found infestation with Diplostomum spp., Dactylogyrus spp., Clinostomum spp., and Piscicola leeches. Water temperature and pH were found fit for rearing fish. Of the 33 fishpond water samples tested, 1 (3%) and 6 (18%) exceeded the recommended limits of <100 mg/L and <0.2 mg/L of nitrate and nitrite, respectively. Of the 29 fishpond water tested, 15 (59%) exceeded the recommended limits of <100 mg/L of total ammonia. *e findings show that the use of raw livestock manure, high fish stocking density, high nitrates and nitrites, and high ammonia levels in fishponds are potential risk factors for fish mortality and acquisition of infectious pathogens in a pond environment in a rural setup, in Central Kenya. *ere is a need to address the above factors in small-scale farming practices to minimize fish loss and also to prevent the occurrence and spread of infectious pathogens.
International Journal of Fisheries and Aquatic Studies, 2019
Bacterial infections cause low to high mortality in fish, affecting the productivity of aquacultu... more Bacterial infections cause low to high mortality in fish, affecting the productivity of aquaculture. This study aimed at determining the occurrence of bacterial pathogens in farmed tilapia, catfish, goldfish and koi carp and source pond water in Kirinyaga County. A total of 181 healthy-appearing fish and 27 water samples from randomly selected fish farms in the county were processed. Bacteriological isolation was done on aseptically collected skin and kidney swabs; gills and a portion of intestines from each fish and water samples. Isolated bacteria were identified by colony morphology, Gram stain and biochemical characteristics, and some further characterized using API-20E kit. A total of 329 bacterial isolates were recovered from fish organs and 39 from pond water samples. They belonged to 17 genera with 18 different identified bacterial species. The most prevalent species found on the skin, gills, intestines, kidney, and water samples belonged to five genera: Proteus spp. (14.9%), Aeromonas hydrophila (8.2%), Aeromonas caviae (6.3%), Plesiomonas (5.2%), Flavobacterium spp. (5.2%), Aeromonas sobria (4.3%) and Micrococcus spp. (4.3%). Some isolates (11%, n=42) could not be identified. Bacterial species recovered from fish samples were also found in the water samples except: Streptococcus spp., Pseudomonas luteola, Serratia plymuthica and Klebsiella oxytoca. Raoultella terrigena was recovered from water samples only. The study has shown that farmed fish and aquatic environments harbor potentially pathogenic and zoonotic bacteria which may cause significant fish diseases and public health risks. Therefore, there is need to implement stringent management and biosecurity programs.
Thermotolerant campylobacters are genetically diverse species; associated with septic abortion in... more Thermotolerant campylobacters are genetically diverse species; associated with septic abortion in cattle, sheep and goats; and bovine mastitis with the most important being Campylobacter jejuni [1]. Campylobacters also poses a significant public health burden, which ultimately result in major costs to the health care system and economic impacts due to lost productivity. Infected poultry are considered the main reservoirs for transferring campylobacters to other farm animals and man. The epidemiology (transmission dynamics regarding what sources, how, and where) of campylobacters in cattle and poultry are poorly comprehended (especially in arid and semi-arid areas including Kajiado County), and has not been fully characterized probably due to ubiquitous and fastidious nature of the organism; as most studies have been carried out at abattoir level. While probable route of transmission in livestock (poultry and cattle) is from contaminated environmental sources (pasture and water) and chicken sources; there’s need to examine the potential role of seasonality and climatic factors. The present study aimed to investigate associations between occurrence of thermotolerant campylobacters in cattle, chicken, water and factors related to climate in Kajiado County
Proceedings of 52nd Kenya Veterinary Association Annual Scientific Conference, 2018
Black spot disease is common in freshwater fish and is usually caused by metacercariae of a digen... more Black spot disease is common in freshwater fish and is usually caused by metacercariae of a digenean trematode, Neascus spp. in the Diplostomidae family. This disease was first encountered in December 2017 in a grow-out Oreochromis niloticus (tilapia) farm with a single liner pond in Kirinyaga Central sub-county, Kirinyaga County. Two (2) mm sized black spots were found in various organs of 10 sampled fish on parasitological examination. However, in a neighbouring farm (<1km away), tilapia in a liner pond were negative for this condition. Risk factors of the disease were assessed through semi-structured questionnaire interview and researchers’ observations of the pond and its environs. A resampling of the farm was conducted in January 2018, where 45 tilapia were collected to determine distribution and intensity of lesions. The black spots from diseased fish were counted on the left side of the fish and multiplied by 2 to determine the intensity. All the sampled tilapia had black spots lesions and percentage distribution in various organs was as follows; fins (43.9%), skin and muscles (23.9%), operculum (8.8%), eyes (2.8%), inside the mouth (2.6%) and gills (1.8%). A mean intensity of 728was recorded and females had higher intensity compared to male fish (p<0.05). Correlation between condition factor and intensity was not statistically significant (p>0.05). Among the risk factors of the disease noted within the farm were presence of snails and piscivorous birds which propagate the life cycle of the parasites. Vegetation such as banana stems which were very close to the ponds were noted to be hiding places for these snails. The dam-liner and the poorly constructed dykes were pervious and this could also pose a risk especially during the rainy season. Black spot disease has an indirect implication on the economic value of fish as those infested are rejected at market level due to aesthetic reasons leading to economic losses. Recommended control measures include use of cover nets over the ponds to prevent interaction of predatory birds which are definitive hosts of digenean trematodes of fish and farming crops such as bananas which harbour snail intermediate hosts in close proximity to fish ponds should be discouraged. Key words: Black spot disease, Neascus spp., metacercariae, predator birds
Proceedings of 52nd Kenya Veterinary Association Annual Scientific Conference, 2018
Some bacteria associated with fish are ubiquitous in aquatic environments but can potentially cau... more Some bacteria associated with fish are ubiquitous in aquatic environments but can potentially cause fish disease(s) especially under stressful intensive farming conditions. The disease(s) may cause mortality, increased production cycle time and thus limit fish production. A study was carried out between December 2017 and March 2018 to investigate common bacterial pathogens of fish in small scale breeder and grow-out fish farms in three sub-counties of Kirinyaga County, Kenya. A total of 106 live fish [43 tilapia (Oreochromis niloticus), 34 catfish (Clarias gariepinus) 23 goldfish (Carassius auratus), and 6 koi carp (Cyprinus carpio carpio)] were purchased from randomly selected fish farms in the study area. Skin and kidney swabs; gills and a portion of intestines were collected aseptically from each fish for bacteriological isolation using standard bacteriological protocols. Isolated bacteria were characterized using colony morphology, Gram staining and biochemical tests. Ninety-nine (99) bacterial isolates were recovered. The Gram negatives comprised genera: Proteus(51%, n=50),Aeromonas (28%, n=28), Pseudomonas (10%, n=10), Citrobacter (3%, n=3), Flavobacterium columnare (3%, n=3), Salmonella(1%, n=1), and Enterobacter (1%, n=1); while Gram positives comprised genera Bacillus (2%, n=2)and Streptococcus (1%, n=1). Aeromonas, Proteus and Pseudomonas organisms were all isolated from all the four fish species studied. Flavobacterium columnare was isolated from tilapia and goldfish. Salmonella and Bacillus organisms were isolated from catfish and tilapia. Citrobacter was isolated from goldfish and catfish while Streptococcus was isolated from tilapia only. Salmonella, Bacillus and Streptococcus organisms were only isolated from fish samples from grow-out farms while Enterobacter organisms were only isolated from breeder farms. All the bacterial species isolated were found on the skin and gills; and in the intestines, which means that they are present in the farmed fish aquatic environments. Organisms of the genera Proteus, Aeromonas, Flavobacterium columnare and Enterobacter were also recovered from the kidney indicating infection after overcoming the fish defense mechanisms. Aeromonas, Salmonella and Streptococcus do not normally cause clinical disease in fish; however they can cause severe illness in humans. Thus in addition to these bacteria being potentially pathogenic to fish, with subsequent reduction in fish productivity, they are a public health hazard. Improvement of husbandry practices and biosecurity at farm level are, therefore, recommended. There is need to undertake more research on use of vaccines and/or probiotics whose effectiveness in improving water quality, immunity, health status, feed conversion efficiency and growth performance of farmed fish has been reported. Keywords: Fish production, Bacterial pathogen, Public health
MSc. Thesis, Sokoine University of Agriculture, 2018
The study aimed at determining the occurrence of pathogenic bacteria in fish and pond water, esta... more The study aimed at determining the occurrence of pathogenic bacteria in fish and pond water, establishing respective antimicrobial susceptibility patterns and risk factors involved with their transmission small scale fish farms in Kirinyaga County. A questionnaire was administered to 92 fish farmers to collect data on farming practices, fish health and related problems. Pond physicochemical parameters were evaluated using standard procedures. Bacteria were isolated from: skin, gills, intestines, and kidney of 181 fish samples (88 tilapia, 53 catfish, 30 goldfish and 10 koi carp) and 27 pond water samples. Isolation and identification of the bacteria was carried out using conventional bacteriological protocols, while further characterization of some isolates was done using Analytic Profile index (API) 20E kit. Antibiotic and disinfectant susceptibility profiles of the some bacterial isolates were established using the disc diffusion and agar well diffusion technique respectively. Most ponds (68%) had plastic liner with monoculture tilapia. Most ponds were fertilized using livestock manure (48%). Most farmers (63%) shared fish nets with other farmers. Knowledge of farmers on basic fish health was poor (57%). Fish diseases were a challenge to 25% of the farms with incidences of fish mortality. The odds ratio (OR) for fish mortality and morbidity were highest in farms where ponds were fertilized using livestock manure (OR = 1.5). The mean±SD of physicochemical parameters were as follows: DO was 6.0±2.8 mg/L, temperature was 25.3±2.9°C, pH was 7.5±0.7, total ammonia was 0.72±1.9 mg/L, nitrate was 29.4±24.5 mg/L, nitrite was 0.27±0.6 mg/L and total phosphorous was 1.12±4.1mg/L. A total of 368 bacterial isolates were recovered from fish organs and water samples; they belonged to 17 genera with at least 18 different bacterial species. The predominant bacterial genera were; Aeromonas (18%), Proteus (15%), Pseudomonas (8%) and Enterobacter (5.7%), while 11% of the isolates could not be identified, with respect to the characterization procedures used. The bacterial isolates showed multiple resistant patterns to at least two antibiotics. Multiple antibiotic resistance index ranged from 0.04 to 0.25 with Streptococcus spp. having the highest score value. All the organisms were sensitive to gentamicin, while cotrimoxazole and ampicillin showed the highest resistance at 73% and 62% respectively. Most of the disinfectants showed antibacterial activity with varying magnitudes. The isolates were 100% sensitive to hydrogen peroxide and formalin at the recommended user-dilution. However, the isolates were resistant to sodium hypochlorite at recommended user-dilution. Farmed fish and their aquatic environments harbors potentially pathogenic and zoonotic bacteria which may cause great economic losses and public health scare, and therefore there is need to implement optimal management, biosafety and biosecurity programs. The results suggest that pond fertilization using livestock manure may be the main risk factor for fish mortality and morbidity The study has shown that some of the bacterial isolates were resistant to common antimicrobials, hence the necessity to ponder this resistance pattern for successful management of fish diseases.
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Papers by Daniel W Wanja
Keywords: Campylobacter; campylobacteriosis; foodborne; livestock; multiple virulence genes; public health; zoonotic
Keywords: Aeromonas hydrophila, aquaculture, fish pathogens, prevalence, wild fish, Zoonosis
Keywords: Biosecurity, fish health, management practices, nile tilapia
Key words: aquaculture productivity, Clinostomum cutaneum, Diplostomum, dissolved oxygen, Neascus
Conference Presentations by Daniel W Wanja
All the sampled tilapia had black spots lesions and percentage distribution in various organs was as follows; fins (43.9%), skin and muscles (23.9%), operculum (8.8%), eyes (2.8%), inside the mouth (2.6%) and gills (1.8%). A mean intensity of 728was recorded and females had higher intensity compared to male fish (p<0.05). Correlation between condition factor and intensity was not statistically significant (p>0.05).
Among the risk factors of the disease noted within the farm were presence of snails and piscivorous birds which propagate the life cycle of the parasites. Vegetation such as banana stems which were very close to the ponds were noted to be hiding places for these snails. The dam-liner and the poorly constructed dykes were pervious and this could also pose a risk especially during the rainy season. Black spot disease has an indirect implication on the economic value of fish as those infested are rejected at market level due to aesthetic reasons leading to economic losses. Recommended control measures include use of cover nets over the ponds to prevent interaction of predatory birds which are definitive hosts of digenean trematodes of fish and farming crops such as bananas which harbour snail intermediate hosts in close proximity to fish ponds should be discouraged.
Key words: Black spot disease, Neascus spp., metacercariae, predator birds
Keywords: Campylobacter; campylobacteriosis; foodborne; livestock; multiple virulence genes; public health; zoonotic
Keywords: Aeromonas hydrophila, aquaculture, fish pathogens, prevalence, wild fish, Zoonosis
Keywords: Biosecurity, fish health, management practices, nile tilapia
Key words: aquaculture productivity, Clinostomum cutaneum, Diplostomum, dissolved oxygen, Neascus
All the sampled tilapia had black spots lesions and percentage distribution in various organs was as follows; fins (43.9%), skin and muscles (23.9%), operculum (8.8%), eyes (2.8%), inside the mouth (2.6%) and gills (1.8%). A mean intensity of 728was recorded and females had higher intensity compared to male fish (p<0.05). Correlation between condition factor and intensity was not statistically significant (p>0.05).
Among the risk factors of the disease noted within the farm were presence of snails and piscivorous birds which propagate the life cycle of the parasites. Vegetation such as banana stems which were very close to the ponds were noted to be hiding places for these snails. The dam-liner and the poorly constructed dykes were pervious and this could also pose a risk especially during the rainy season. Black spot disease has an indirect implication on the economic value of fish as those infested are rejected at market level due to aesthetic reasons leading to economic losses. Recommended control measures include use of cover nets over the ponds to prevent interaction of predatory birds which are definitive hosts of digenean trematodes of fish and farming crops such as bananas which harbour snail intermediate hosts in close proximity to fish ponds should be discouraged.
Key words: Black spot disease, Neascus spp., metacercariae, predator birds
Isolated bacteria were characterized using colony morphology, Gram staining and biochemical tests. Ninety-nine (99) bacterial isolates were recovered. The Gram negatives comprised genera: Proteus(51%, n=50),Aeromonas (28%, n=28), Pseudomonas (10%, n=10), Citrobacter (3%, n=3), Flavobacterium columnare (3%, n=3), Salmonella(1%, n=1), and Enterobacter (1%, n=1); while Gram positives comprised genera Bacillus (2%, n=2)and Streptococcus (1%, n=1). Aeromonas, Proteus and Pseudomonas organisms were all isolated from all the four fish species studied. Flavobacterium columnare was isolated from tilapia and goldfish. Salmonella and Bacillus organisms were isolated from catfish and tilapia. Citrobacter was isolated from goldfish and catfish while Streptococcus was isolated from tilapia only. Salmonella, Bacillus and Streptococcus organisms were only isolated from fish samples from grow-out farms while Enterobacter organisms were only isolated from breeder farms. All the bacterial species isolated were found on the skin and gills; and in the intestines, which means that they are present in the farmed fish aquatic environments. Organisms of the genera Proteus, Aeromonas, Flavobacterium columnare and Enterobacter were also recovered from the kidney indicating infection after overcoming the fish defense mechanisms. Aeromonas, Salmonella and Streptococcus do not normally cause clinical disease in fish; however they can cause severe illness in humans. Thus in addition to these bacteria being potentially pathogenic to fish, with subsequent reduction in fish productivity, they are a public health hazard. Improvement of husbandry practices and biosecurity at farm level are, therefore, recommended. There is need to undertake more research on use of vaccines and/or probiotics whose effectiveness in improving water quality, immunity, health status, feed conversion efficiency and growth performance of farmed fish has been reported.
Keywords: Fish production, Bacterial pathogen, Public health