I am veterinarian, a professor in Veterinary Epidemiology; my research interest are infectious diseases (either zoonotic or not) like leptospira, BLV- BVDV- Hemobacterias, COVID 19 and others, mathematical modelling of diseases coupled with health economics and understanding and quantifying transmission. Address: Instituto Medicina Preventiva Veterinaria Facultad de Ciencias Veterinarias Edificio Saelzer 5 Piso Campus Isla Teja Valdivia- Chile
Revista Brasileira de Parasitologia Veterinária, 2021
This study aimed to investigate the genetic diversity of Hepatozoon spp. in rodents from Valdivia... more This study aimed to investigate the genetic diversity of Hepatozoon spp. in rodents from Valdivia, Chile. A total of 74 rodents (synanthropic n=38; wild n=36) were trapped in Valdivia. We performed conventional PCR assays for Apicomplexa organisms targeting two overlapping 18S rDNA gene fragments (600 bp and 900 bp) followed by sequencing of selected amplicons. Hepatozoon spp. occurrence was 82.43% (61/74). Twelve sequences obtained from the 600 bp and ten from the 900 bp 18S rDNA fragments were identified as Hepatozoon sp. Six sequences obtained from 18S rDNA-based overlapping PCR protocols were used for concatenated (1,400 bp) phylogenetic, haplotype and distance analyses. Hepatozoon spp. 18S rDNA concatenated sequences from the present study were detected in Oligoryzomys longicaudatus, Rattus norvegicus, Mus musculus, and Abrothrix longipilis grouped with Hepatozoon species earlier described in rodents and reptiles from Chile and Brazil. Nucleotide polymorphism of the six 18S rDN...
Pathogenic Leptospira spp. are zoonotic bacteria that infect wild and domestic animals. Humans co... more Pathogenic Leptospira spp. are zoonotic bacteria that infect wild and domestic animals. Humans contract leptospirosis directly through contact with infected animals or indirectly from contaminated water or soil. In mammalian reservoirs, the pathogen can colonize renal tubules for lengthy periods and persistently contaminate the environment through urine. Cattle have been reported to shed several serovars; with Hardjo the most common serovar found in cattle. Without clinical manifestations, the infection can spread within a herd, impairing productivity, and putting workers like farmers, abattoir operators and veterinarians at risk. The dynamics of pathogenic Leptospira shedding was studied in six dairy herds in southern Chile. Various intermittent urine shedding patterns were found, with elimination periods between 79 and 259 days and bacterial loads ranging from 3 × 104 to 4.4 × 104 bacteria/mL. The current study was the first to assess the various urine shedding patterns and loads ...
Leptospirosis is a globally disseminated zoonotic disease with no national surveillance systems. ... more Leptospirosis is a globally disseminated zoonotic disease with no national surveillance systems. On the other hand, surveillance is crucial for improving population health, and surveillance systems produce data that motivates action. Unfortunately, like many other countries, Ecuador put in place a monitoring system that has never been tested. The goal of this study was to use scenario tree modeling to assess the sensitivity of Ecuador's current national surveillance system to human leptospirosis as the basis for an economic assessment of the system. We created a decision-tree model to analyze the current system's sensitivity. The inputs were described as probabilities distributions, and the model assessed the program's sensitivity as an output. The model also considers the geographical and weather variations across Ecuador's three continental regions: Andean, Amazonia, and the Coast. Several data sources were used to create the model, including leptospirosis records ...
Journal of veterinary medicine and research, Nov 1, 2018
Background: Infection by Leptospira is relevant in canine medicine. However, prospective studies ... more Background: Infection by Leptospira is relevant in canine medicine. However, prospective studies about leptospirosis in dogs are scarce worldwide. Methods: A prospective study among owned domestic dogs from southern Chile was performed by the Microscopic Agglutination Test: 1) to estimate the rate of serological conversion for anti-Leptospira antibodies in a 6 to 9 month follow-up period, 2) to determine the reactive serovars and, 3) to measure antibody titers in seropositive dogs. There were two samplings: in the first, 192 animals were sampled and 50 re-sampled dogs constituted the second. Results: The rate of serological conversion in the follow-up period was 12.0% (95% Confidence Interval=2.9-21.0%). In the first sampling, the most reactive serovars were Ballum and Canicola. In the second sampling, the most reactive serovar was Icterohaemorragiae. In both samplings, the antibody titers ranged between 1:100 and 1:800, with predominance titers of 1:100 and 1:200. Conclusions: The relatively high rate of serological conversion suggests that the exposure to Leptospira in dogs is present in southern Chile, with a possible endemic presentation of the seropositivity. Preventive measures such as vaccination and to reduce the exposition of pet dogs to reservoirs of the bacteria must be taken, as well to increase the awareness about Leptospira infection among public health institutions, veterinary practitioners and dog owners.
Bovine leukemia virus (BLV) is a retrovirus that affects cattle worldwide. A longitudinal study w... more Bovine leukemia virus (BLV) is a retrovirus that affects cattle worldwide. A longitudinal study was conducted with the aim to (a) estimate the incidence rate of the BLV infection of dairy farms in the regions of Los Ríos and Los Lagos (Chile), and (b) describe the frequency and epidemiological association of risk management practices related to new cases in cattle on dairy farms in Southern Chile. Infection status was based on commercial blocking ELISA results, on serum and milk. Individual information on animals and management practices was extracted from farm records, and then the most likely date of infection for new cases was estimated. The number of new infections was used to calculate the within-herd incidence rate. Adult animals had an incidence rate of 1.16 (95% CI 0.96; 1.20) cases per 100 cow-months at risk, while for young animals it was 0.64 (95% CI 0.44; 1.00) cases per 100 animal-months at risk. Rectal palpation, artificial insemination, and injections were the most co...
Leptospirosis is a ubiquitous distributed zoonotic infectious disease present in wild and domesti... more Leptospirosis is a ubiquitous distributed zoonotic infectious disease present in wild and domestic animals. This study aimed to estimate within-herd and herd-level seroprevalence against pathogenic Leptospira spp. in dairy cows from southern Chile and identify risk factors associated with the herd-level status. We used a multi-stage strategy combined with a stratified sample strategy for randomly sampling 147 herds and 4876 lactating cows. We considered as infected a herd with at least one positive reactor to MAT. In addition, an epidemiological survey was applied to the herd’s owners and a logistic regression (LR) model was constructed to analyze it. The overall within-herd prevalence was 5.9% (95% CI 4.9–6.8), the overall herd-level prevalence was 42.2% (95% CI 9.2–47.9), and there was variation in both between different herd sizes. L. borgpetersenii serovars Hardjo and Tarassovi and L. interrogans serovar Pomona were the more frequent serovars in non-vaccinated herds. A factor th...
This study aims to assess calf usage of five potential enrichment devices provided simultaneously... more This study aims to assess calf usage of five potential enrichment devices provided simultaneously. We used 25 weaned Holstein-Friesian calves housed in groups of five (five replicates), and their behavior was recorded continuously with video cameras. This longitudinal observational study used a pen equipped with a mechanical and fixed brush, cowhide, and horizontal and vertical ropes. Data collected included how many visits each object received per day, the type of object usage, and the duration of the visits. Calves used all five objects at least once, and they used items more during the daytime than at night. Brushes were used mainly for grooming (e.g., rubbing or scratching), while ropes and cowhide for oral interactions (e.g., licking, chewing, and biting), most likely to lack oral stimulations that would naturally be satisfied by suckling and grazing at this age. The objects most frequently used were the mechanical brush and the horizontal rope, and they received the highest nu...
This study aimed to screen wild rodents from southern Chile, for the presence of Anaplasmatacea. ... more This study aimed to screen wild rodents from southern Chile, for the presence of Anaplasmatacea. Spleen samples from 33 wild rodents trapped in Valdivia Province were screened by conventional PCR (cPCR), targeting the Anaplasmataceae 16S rRNA gene (16S). Positive samples were further evaluated, targeting a larger 16S fragment, groEL operon, and gltA gene, followed by sequencing and phylogenetic analysis. Anaplasmataceae DNA was detected in 15% (five of 33) of the tested rodents (Abrothrix sp. [four of five] and Mus musculus [one of five]). Analysis of sequenced products based on the 16S gene revealed high similarity with "Ca. Neoehrlichia mikurensis," "Ca. Neoehrlichia lotoris" and "Ca. Neoehrlichia arcana" (97.8%-98.6%). A lower similarity was observed with Candidatus Neoehrlichia groEL (89.7%-92%) and gltA (79.5%-79.9%) loci. According to the 16SrRNA, groEL and gltA phylogenetic analyses, two closely related genotypes of "Candidatus Neoehrlichia&...
Factors related with leptospirosis in domestic dogs have been reported worldwide. The aims of thi... more Factors related with leptospirosis in domestic dogs have been reported worldwide. The aims of this study were to identify factors associated with this disease described in different observational studies and to combine the coinciding factors in at least four studies using meta‐analyses, to obtain a pooled odds ratio (OR) as measure of infection risk. A literature search was performed in electronic databases, electronic databases of specific journals and search engines to find studies published in English, Spanish and Portuguese available from January 1960 to January 2015. Two hundred and eighteen factors were identified in 31 publications including cross‐sectional and case–control studies. Finally, independent meta‐analyses were performed with six different variables, which included between 4 and 8 articles. The pooled OR indicated that the variables ‘mixed‐breed dogs’, ‘flooding occurrence in the habitat of the dog’ and ‘working dogs’ were risk factors for leptospirosis, while ‘being a dog less than 1 year old’ was a protective factor; however, all these associations were not statistically significant. Otherwise, the variables ‘male dog’ and ‘urban dog’ were statistically significant risk factors for infection. This study highlights the need for more formal studies on the epidemiology of canine leptospirosis. Nevertheless, the study revealed that some risk factors for infection coincided in different observational studies. These factors could be considered to raise suspicion about the disease, especially when there is a history of exposure to the bacteria.
Mycobacterium avium subsp. paratuberculosis (MAP) causes a chronic intestinal infection mainly in... more Mycobacterium avium subsp. paratuberculosis (MAP) causes a chronic intestinal infection mainly in domestic and wild ruminants and is transmitted primarily by the fecal-oral route. Mycobacterium bovis (M. bovis) produces a chronic infection principally of the respiratory system. It affects most domestic mammals, wild species, and humans and is spread via the respiratory or oral route. It is important to note that M. bovis is considered a major zoonotic agent. The term coinfection refers to the coexistence of two or more infectious agents in the same host. The goal of the present study was to assess management factors that may favor coinfection with MAP and M. bovis in cattle at an individual level. A cross-sectional study was conducted including 366 cattle from 11 herds. Diagnostic information for both pathogens and individual characteristics of the animals and management practices applied on them was collected from each herd. The results indicated a set of variables being more frequent in the coinfected group of animals and mainly related with biosecurity measures. This study provided regionally based data that may be used to design future control plans for both cattle infections in southern Chile.
Revista Brasileira de Parasitologia Veterinária, 2021
This study aimed to investigate the genetic diversity of Hepatozoon spp. in rodents from Valdivia... more This study aimed to investigate the genetic diversity of Hepatozoon spp. in rodents from Valdivia, Chile. A total of 74 rodents (synanthropic n=38; wild n=36) were trapped in Valdivia. We performed conventional PCR assays for Apicomplexa organisms targeting two overlapping 18S rDNA gene fragments (600 bp and 900 bp) followed by sequencing of selected amplicons. Hepatozoon spp. occurrence was 82.43% (61/74). Twelve sequences obtained from the 600 bp and ten from the 900 bp 18S rDNA fragments were identified as Hepatozoon sp. Six sequences obtained from 18S rDNA-based overlapping PCR protocols were used for concatenated (1,400 bp) phylogenetic, haplotype and distance analyses. Hepatozoon spp. 18S rDNA concatenated sequences from the present study were detected in Oligoryzomys longicaudatus, Rattus norvegicus, Mus musculus, and Abrothrix longipilis grouped with Hepatozoon species earlier described in rodents and reptiles from Chile and Brazil. Nucleotide polymorphism of the six 18S rDN...
Pathogenic Leptospira spp. are zoonotic bacteria that infect wild and domestic animals. Humans co... more Pathogenic Leptospira spp. are zoonotic bacteria that infect wild and domestic animals. Humans contract leptospirosis directly through contact with infected animals or indirectly from contaminated water or soil. In mammalian reservoirs, the pathogen can colonize renal tubules for lengthy periods and persistently contaminate the environment through urine. Cattle have been reported to shed several serovars; with Hardjo the most common serovar found in cattle. Without clinical manifestations, the infection can spread within a herd, impairing productivity, and putting workers like farmers, abattoir operators and veterinarians at risk. The dynamics of pathogenic Leptospira shedding was studied in six dairy herds in southern Chile. Various intermittent urine shedding patterns were found, with elimination periods between 79 and 259 days and bacterial loads ranging from 3 × 104 to 4.4 × 104 bacteria/mL. The current study was the first to assess the various urine shedding patterns and loads ...
Leptospirosis is a globally disseminated zoonotic disease with no national surveillance systems. ... more Leptospirosis is a globally disseminated zoonotic disease with no national surveillance systems. On the other hand, surveillance is crucial for improving population health, and surveillance systems produce data that motivates action. Unfortunately, like many other countries, Ecuador put in place a monitoring system that has never been tested. The goal of this study was to use scenario tree modeling to assess the sensitivity of Ecuador's current national surveillance system to human leptospirosis as the basis for an economic assessment of the system. We created a decision-tree model to analyze the current system's sensitivity. The inputs were described as probabilities distributions, and the model assessed the program's sensitivity as an output. The model also considers the geographical and weather variations across Ecuador's three continental regions: Andean, Amazonia, and the Coast. Several data sources were used to create the model, including leptospirosis records ...
Journal of veterinary medicine and research, Nov 1, 2018
Background: Infection by Leptospira is relevant in canine medicine. However, prospective studies ... more Background: Infection by Leptospira is relevant in canine medicine. However, prospective studies about leptospirosis in dogs are scarce worldwide. Methods: A prospective study among owned domestic dogs from southern Chile was performed by the Microscopic Agglutination Test: 1) to estimate the rate of serological conversion for anti-Leptospira antibodies in a 6 to 9 month follow-up period, 2) to determine the reactive serovars and, 3) to measure antibody titers in seropositive dogs. There were two samplings: in the first, 192 animals were sampled and 50 re-sampled dogs constituted the second. Results: The rate of serological conversion in the follow-up period was 12.0% (95% Confidence Interval=2.9-21.0%). In the first sampling, the most reactive serovars were Ballum and Canicola. In the second sampling, the most reactive serovar was Icterohaemorragiae. In both samplings, the antibody titers ranged between 1:100 and 1:800, with predominance titers of 1:100 and 1:200. Conclusions: The relatively high rate of serological conversion suggests that the exposure to Leptospira in dogs is present in southern Chile, with a possible endemic presentation of the seropositivity. Preventive measures such as vaccination and to reduce the exposition of pet dogs to reservoirs of the bacteria must be taken, as well to increase the awareness about Leptospira infection among public health institutions, veterinary practitioners and dog owners.
Bovine leukemia virus (BLV) is a retrovirus that affects cattle worldwide. A longitudinal study w... more Bovine leukemia virus (BLV) is a retrovirus that affects cattle worldwide. A longitudinal study was conducted with the aim to (a) estimate the incidence rate of the BLV infection of dairy farms in the regions of Los Ríos and Los Lagos (Chile), and (b) describe the frequency and epidemiological association of risk management practices related to new cases in cattle on dairy farms in Southern Chile. Infection status was based on commercial blocking ELISA results, on serum and milk. Individual information on animals and management practices was extracted from farm records, and then the most likely date of infection for new cases was estimated. The number of new infections was used to calculate the within-herd incidence rate. Adult animals had an incidence rate of 1.16 (95% CI 0.96; 1.20) cases per 100 cow-months at risk, while for young animals it was 0.64 (95% CI 0.44; 1.00) cases per 100 animal-months at risk. Rectal palpation, artificial insemination, and injections were the most co...
Leptospirosis is a ubiquitous distributed zoonotic infectious disease present in wild and domesti... more Leptospirosis is a ubiquitous distributed zoonotic infectious disease present in wild and domestic animals. This study aimed to estimate within-herd and herd-level seroprevalence against pathogenic Leptospira spp. in dairy cows from southern Chile and identify risk factors associated with the herd-level status. We used a multi-stage strategy combined with a stratified sample strategy for randomly sampling 147 herds and 4876 lactating cows. We considered as infected a herd with at least one positive reactor to MAT. In addition, an epidemiological survey was applied to the herd’s owners and a logistic regression (LR) model was constructed to analyze it. The overall within-herd prevalence was 5.9% (95% CI 4.9–6.8), the overall herd-level prevalence was 42.2% (95% CI 9.2–47.9), and there was variation in both between different herd sizes. L. borgpetersenii serovars Hardjo and Tarassovi and L. interrogans serovar Pomona were the more frequent serovars in non-vaccinated herds. A factor th...
This study aims to assess calf usage of five potential enrichment devices provided simultaneously... more This study aims to assess calf usage of five potential enrichment devices provided simultaneously. We used 25 weaned Holstein-Friesian calves housed in groups of five (five replicates), and their behavior was recorded continuously with video cameras. This longitudinal observational study used a pen equipped with a mechanical and fixed brush, cowhide, and horizontal and vertical ropes. Data collected included how many visits each object received per day, the type of object usage, and the duration of the visits. Calves used all five objects at least once, and they used items more during the daytime than at night. Brushes were used mainly for grooming (e.g., rubbing or scratching), while ropes and cowhide for oral interactions (e.g., licking, chewing, and biting), most likely to lack oral stimulations that would naturally be satisfied by suckling and grazing at this age. The objects most frequently used were the mechanical brush and the horizontal rope, and they received the highest nu...
This study aimed to screen wild rodents from southern Chile, for the presence of Anaplasmatacea. ... more This study aimed to screen wild rodents from southern Chile, for the presence of Anaplasmatacea. Spleen samples from 33 wild rodents trapped in Valdivia Province were screened by conventional PCR (cPCR), targeting the Anaplasmataceae 16S rRNA gene (16S). Positive samples were further evaluated, targeting a larger 16S fragment, groEL operon, and gltA gene, followed by sequencing and phylogenetic analysis. Anaplasmataceae DNA was detected in 15% (five of 33) of the tested rodents (Abrothrix sp. [four of five] and Mus musculus [one of five]). Analysis of sequenced products based on the 16S gene revealed high similarity with "Ca. Neoehrlichia mikurensis," "Ca. Neoehrlichia lotoris" and "Ca. Neoehrlichia arcana" (97.8%-98.6%). A lower similarity was observed with Candidatus Neoehrlichia groEL (89.7%-92%) and gltA (79.5%-79.9%) loci. According to the 16SrRNA, groEL and gltA phylogenetic analyses, two closely related genotypes of "Candidatus Neoehrlichia&...
Factors related with leptospirosis in domestic dogs have been reported worldwide. The aims of thi... more Factors related with leptospirosis in domestic dogs have been reported worldwide. The aims of this study were to identify factors associated with this disease described in different observational studies and to combine the coinciding factors in at least four studies using meta‐analyses, to obtain a pooled odds ratio (OR) as measure of infection risk. A literature search was performed in electronic databases, electronic databases of specific journals and search engines to find studies published in English, Spanish and Portuguese available from January 1960 to January 2015. Two hundred and eighteen factors were identified in 31 publications including cross‐sectional and case–control studies. Finally, independent meta‐analyses were performed with six different variables, which included between 4 and 8 articles. The pooled OR indicated that the variables ‘mixed‐breed dogs’, ‘flooding occurrence in the habitat of the dog’ and ‘working dogs’ were risk factors for leptospirosis, while ‘being a dog less than 1 year old’ was a protective factor; however, all these associations were not statistically significant. Otherwise, the variables ‘male dog’ and ‘urban dog’ were statistically significant risk factors for infection. This study highlights the need for more formal studies on the epidemiology of canine leptospirosis. Nevertheless, the study revealed that some risk factors for infection coincided in different observational studies. These factors could be considered to raise suspicion about the disease, especially when there is a history of exposure to the bacteria.
Mycobacterium avium subsp. paratuberculosis (MAP) causes a chronic intestinal infection mainly in... more Mycobacterium avium subsp. paratuberculosis (MAP) causes a chronic intestinal infection mainly in domestic and wild ruminants and is transmitted primarily by the fecal-oral route. Mycobacterium bovis (M. bovis) produces a chronic infection principally of the respiratory system. It affects most domestic mammals, wild species, and humans and is spread via the respiratory or oral route. It is important to note that M. bovis is considered a major zoonotic agent. The term coinfection refers to the coexistence of two or more infectious agents in the same host. The goal of the present study was to assess management factors that may favor coinfection with MAP and M. bovis in cattle at an individual level. A cross-sectional study was conducted including 366 cattle from 11 herds. Diagnostic information for both pathogens and individual characteristics of the animals and management practices applied on them was collected from each herd. The results indicated a set of variables being more frequent in the coinfected group of animals and mainly related with biosecurity measures. This study provided regionally based data that may be used to design future control plans for both cattle infections in southern Chile.
Shedding of DNA of pathogenic Leptospira spp. has been documented in naturally infected cats in s... more Shedding of DNA of pathogenic Leptospira spp. has been documented in naturally infected cats in several countries, but urinary shedding of infectious Leptospira spp. has only recently been proven. The climate in Southern Chile is temperate rainy with high annual precipita-tions which represents ideal preconditions for survival of Leptospira spp., especially during spring and summer. The aims of this study were to investigate shedding of pathogenic Lep-tospira spp. in outdoor cats in Southern Chile, to perform molecular characterization of isolates growing in culture, and to assess potential risk factors associated with shedding. Urine samples of 231 outdoor cats from rural and urban areas in southern Chile were collected. Urine samples were investigated for pathogenic Leptospira spp. by 4 techniques: qPCR targeting the lipL32 gene, immunomagnetic separation (IMS)-coupled qPCR (IMS-qPCR), direct culture and IMS-coupled culture. Positive urine cultures were additionally confirmed by PCR. Multilocus sequence typing (MLST) was used to molecularly characterize isolates obtained from positive cultures. Overall, 36 urine samples (15.6%, 95% confidence interval (CI) 11.4-20.9) showed positive results. Eighteen (7.8%, 95% CI 4.9-12.1), 30 (13%, 95% CI 9.2-18), 3 (1.3%, 0.3-3.9) and 4 cats (1.7%; 95% CI 0.5-4.5) were positive in qPCR, IMS-qPCR, conventional culture, and IMS-coupled culture, respectively. MLST results of 7 culture-positive cats revealed sequences that could be assigned to sequence type 17 (6 cats) and sequence type 27 (1 cat) corresponding to L. interrogans (Pathogenic Leptospira Subgroup 1). Shedding of pathogenic Leptospira spp. by cats might be an underestimated source of infection for other species including humans. The present study is the first one reporting growth of leptospires from feline urine in culture in naturally infected cats in South-America and characterisation of culture-derived isolates. So far, very few cases of successful attempts to culture leptospires from naturally infected cats are described worldwide.
A domestic cat dwelling in a dairy cattle farm with haematuria was referred for a
physical exami... more A domestic cat dwelling in a dairy cattle farm with haematuria was referred for a
physical examination. The examination showed no abnormalities; therefore, complementary exams were performed. Leukocytosis with neutrophilia, monocytosis and hyperproteinaemia were detected. The urine analysis showed a bacterial infection without ultrasound findings. Serological titers to Leptospira interrogans serovar Pomona and Autumnalis were detected. Molecular analysis demonstrated the presence of Leptospira spp. in urine. The findings were consistent with subclinical leptospirosis. The cattle herd had evidence of Leptospira infection. The microbiological exams confirmed the presence of the Leptospira spp. in urine and serum. According to the evidence presented in this study, cats that dwell within a dairy farm could play a role in the
Leptospira infection epidemiologically. The importance of feline leptospirosis must be evaluated with leptospirosis control in livestock
Leptospirosis is caused by pathogenic Leptospira, and synanthropic and wildlife species of rodent... more Leptospirosis is caused by pathogenic Leptospira, and synanthropic and wildlife species of rodents are an important source of infection; however, much of the information about infection progression was obtained from murine models. The aim of this study was to assess infection status and risk factors associated with pathogenic Leptospira in synanthropic and wild rodent species and describe histopathological lesions in several organs from naturally infected animals. In a cross-sectional study, 121 rodents from three synanthropic species and two wild species were trapped in dairy farms in Southern Chile. Liver, heart, kidney, and lungs from trapped animals were fixed in formalin and stained with hematoxylin–eosin. Tissues with lesions consistent with Leptospira infection were tested by immunohistochemistry (IHC) and real-time polymerase chain reaction (qPCR) using the LipL32 antigen. Risk factors were assessed by a conditional mixed-logistic regression model. More than half (56.7%) of the negative reactors to the microscopic agglutination test were identified as infected either by IHC/qPCR. A lower risk of infection compared to the rest of the seasons was found in the fall, and the synanthropic species have a lower risk of infection in comparison with the wildlife species. IHC and qPCR contributed to the identification of pathogenic Leptospira in related histological lesions and 50% more infections than serology.
Factors related with leptospirosis in domestic dogs have been reported worldwide.
The aims of th... more Factors related with leptospirosis in domestic dogs have been reported worldwide.
The aims of this study were to identify factors associated with this disease
described in different observational studies and to combine the coinciding factors
in at least four studies using meta-analyses, to obtain a pooled odds ratio (OR) as
measure of infection risk. A literature search was performed in electronic databases,
electronic databases of specific journals and search engines to find studies
published in English, Spanish and Portuguese available from January 1960 to January
2015. Two hundred and eighteen factors were identified in 31 publications
including cross-sectional and case–control studies. Finally, independent metaanalyses
were performed with six different variables, which included between 4
and 8 articles. The pooled OR indicated that the variables ‘mixed-breed dogs’,
‘flooding occurrence in the habitat of the dog’ and ‘working dogs’ were risk
factors for leptospirosis, while ‘being a dog less than 1 year old’ was a protective
factor; however, all these associations were not statistically significant. Otherwise,
the variables ‘male dog’ and ‘urban dog’ were statistically significant risk factors
for infection. This study highlights the need for more formal studies on the epidemiology
of canine leptospirosis. Nevertheless, the study revealed that some risk
factors for infection coincided in different observational studies. These factors
could be considered to raise suspicion about the disease, especially when there is
a history of exposure to the bacteria
Leptospirosis is an emerging zoonotic disease of worldwide distribution. A
cross-sectional study... more Leptospirosis is an emerging zoonotic disease of worldwide distribution. A
cross-sectional study was conducted in urban and rural environments in southern Chile
(1) to detect domestic cats with serologic evidence of exposure to Leptospira spp.; (2) to
determine the prevalence of anti-Leptospira antibodies; (3) to describe seroprevalences
according to different characteristics of the animals, and (4) to identify risk factors
associated with the seropositivity in the Microscopic Agglutination Test (MAT). Blood
samples were taken from 124 owned cats. A frequentist and Bayesian approach were
applied for prevalence estimation. The overall apparent prevalence of anti-Leptospira antibodies was 8.1% (95% Confident Interval = 3.9–4.3). With the Bayesian approach, the
overall True Prevalence (TP) was 5.2% (95% Credibility Interval (CrI) = 0.6–12.4). The
TP for urban cats was 1.8% (95% CrI = 0.1–7.2) and the TP for rural felines was 25.2%
(95% CrI = 9.3–46.6). Cats that live in a place where agricultural activities are performed
with water that flows in streams or backwater and cats that live in places near flooded areas
had a higher risk of seropositivity in MAT. The exposure to Leptospira spp. in domestic
cats of urban and rural origin in Southern Chile is a public health concern that requires an
increased awareness and the implementation of preventive measures
Background: Infection by Leptospira is relevant in canine medicine. However, prospective studies ... more Background: Infection by Leptospira is relevant in canine medicine. However, prospective studies about leptospirosis in dogs are scarce worldwide.
Methods: A prospective study among owned domestic dogs from southern Chile was performed by the Microscopic Agglutination Test: 1) to estimate
the rate of serological conversion for anti-Leptospira antibodies in a 6 to 9 month follow-up period, 2) to determine the reactive serovars and, 3) to measure
antibody titers in seropositive dogs. There were two samplings: in the first, 192 animals were sampled and 50 re-sampled dogs constituted the second.
Results: The rate of serological conversion in the follow-up period was 12.0% (95% Confidence Interval=2.9-21.0%). In the first sampling, the most
reactive serovars were Ballum and Canicola. In the second sampling, the most reactive serovar was Icterohaemorragiae. In both samplings, the antibody titers
ranged between 1:100 and 1:800, with predominance titers of 1:100 and 1:200.
Conclusions: The relatively high rate of serological conversion suggests that the exposure to Leptospira in dogs is present in southern Chile, with a possible
endemic presentation of the seropositivity. Preventive measures such as vaccination and to reduce the exposition of pet dogs to reservoirs of the bacteria must
be taken, as well to increase the awareness about Leptospira infection among public health institutions, veterinary practitioners and dog owners.
Leptospirosis is a zoonotic disease of worldwide distribution caused by spirochetes of the genus ... more Leptospirosis is a zoonotic disease of worldwide distribution caused by spirochetes of the genus Leptospira. The genus includes a large number of
serovars that may be sheed in the urine of infected animals creating a highly infectious source of transmission. Numerous species of wild and domestic
mammals act as maintenance hosts and form reservoirs of the bacteria, with other species being incidental hosts that may develop the disease. In dogs
and cats, the disease is caused by different serovars and while dogs act as maintenance host for some serovars, both species are incidental host for
others. Dogs and cats may have frequent contact with wild and domestic farm animals, therefore they are an important link in the transmission route.
Leptospira may survive in the environment which increases the complexity of the epidemiology. The presentation of the disease can be highly variable
and, particularly for feline leptospirosis, not well described. Laboratory testing is essential for the diagnosis, however, it is complicated due to the need
to discriminate between Leptospira infection in animals with clinical disease from leptospiral specific antibody responses in maintenance hosts, or in
animals with subclinical infection. Infection in pets may have important economic and public health implications and because of the risk of transmission
from pets to their owners and to other animals, preventive measures need to be applied and an increased awareness is adviced
A cross-sectional study using 99 serum samples of dogs from southern Chile was conducted to deter... more A cross-sectional study using 99 serum samples of dogs from southern Chile was conducted to determine the diagnostic utility of a rapid immunochromatography assay for the detection of Leptospira specific IgM antibodies as screening test and as a potential aid in the diagnosis of leptospirosis in animals with and without clinical suspicion of the disease.
The Microscopic Agglutination Test (MAT) was used as reference assay. Anti-Leptospira
antibodies were detected in 37.3% of the dogs with MAT. Using the immunochromatography test, specific IgM antibodies were found in 13.1% of sampled dogs. The sensitivity of the rapid test as screening assay was 29.7% (95% Confidence Interval=16.4-47.2) and the specificity was 96.7% (95% Confidence Interval=87.8-99.4). 40.0% of the canines with clinical suspicion of leptospirosis and 37.1% of dogs without clinical signs were serological reactors to MAT, but none of MAT reactive dogs with clinical suspicion tested positive in the rapid test. Rapid and user-friendly diagnostic procedures for canine leptospirosis such as this immunochromatography assay could be important tools to use in clinical practice, however, further studies are needed to obtain more information about their utility, considering that diagnostic tests could not have similar performances in different geographic locations, clinical and epidemiological contexts
Even though hemotrophic mycoplasma (hemoplasma) infections are well documented in a wide variety ... more Even though hemotrophic mycoplasma (hemoplasma) infections are well documented in a wide variety of hosts worldwide, there is a gap in the knowledge aobut hemoplasmas in rodents. This study aimed to molecularly survey and investigate the genetic diversity of hemoplasmas in rodents from Chile. Synanthropic and wild rodents (n = 74) were captured in the southern province of Valdivia (Corral, Valdivia, Riñihue, and Reumén localities). Spleen samples were submitted to a conventional PCR for hemotrophic Mycoplasma spp. targeting the 16S rRNA gene (800 bp), followed by sequencing, phylogenetic, and genetic diversity analyses. The overall occurrence of hemotrophic mycoplasmas in rodents from Valdivia was 24.5% (18/74) [95% CI (14.5; 34.1)]. Hemoplasmas were detected in Mus musculus (1/4), Rattus norvegicus (1/16), Abrothrix longipilis (7/13), A. olivaceo (6/8), and Oligoryzomys longicaudatus (3/10). The nucleotide polymorphism analysis of the targeted 16S rRNA region showed low diversity, with two genotypes and a high identity to the variants detected in wild rodents from Brazil. Hemoplasmas are described for the first time in rodents from Chile with a moderate occurrence and low 16S rDNA genetic diversity within the sampled rodent population. The detected hemoplasma genotypes were specific to rodents and were not shared with other mammals.
The aim of this study was to molecularly survey Bartonella spp. in rodents from the Valdivia Prov... more The aim of this study was to molecularly survey Bartonella spp. in rodents from the Valdivia Province, Southern Chile and from wild black rat-fleas in Guafo Island, Chilean Patagonia. Thrity-three spleens from synanthropic (Mus musculus, Rattus novergicus and Rattus rattus) and wild (Abrothrix longipilis, Oligoryzomys longicaudatus, Abrothrix sp.) rodents from Valdivia and 39 fleas/flea-pools (Plocopsylla sp. and Nosopsyllus sp.) from R. rattus in Guafo Island were obtained. All samples were screened by high-resolution melting (HRM) real-time PCR for Bartonella ITS locus (190 bp). ITS-Positive samples were further analyzed for two HRM real-time PCR assays targeting Bartonella rpoB (191 bp) and gltA (340 bp) gene fragments. All positive ITS, gltA and rpoB real-time PCR products were purified and sequenced. Bayesian inference trees were built for the gltA and rpoB gene fragments. Bartonella-ITS DNA was detected in 36.3% (12/33) [95% CI (22-53%)] of the tested rodents from Valdivia, being identified in all but O. longicaudatus rodent species captured in this study. ITS DNA was detected in 28% (11/39) [95% CI (16-43%)] of fleas/flea-pools from Guafo Island and identified in both Plocopsylla and Nosopsyllus genera. Sequencing and phylogenic analyses targeting three loci of Bartonella spp. allowed the identification of five genotypes in rodents from Southern Chile, potentially belonging to three different Bartonella spp. Those included Bartonella tribocorum identified from R. rattus, Bartonella rochalimae detected from Abrothix sp., and one novel genotype from uncharacterized Bartonella sp. identified in M. musculus, R. norvegicus, A. longipilis, and Abothrix sp., related to strains previously isolated in Phyllotis sp. from Peru. Additionally, two genotypes of B. tribocorum were identified in fleas from Guafo. In a nutshell, highly diverse and potentially zoonotic Bartonella spp. are described for the first time in wild and synanthropic rodents from Chile, and B. tribocorum was detected in wild back rat fleas from Guafo Island.
This study aimed to screen wild rodents from southern Chile, for the presence of
Anaplasmatacea.... more This study aimed to screen wild rodents from southern Chile, for the presence of
Anaplasmatacea. Spleen samples from 33 wild rodents trapped in Valdivia Province
were screened by conventional PCR (cPCR), targeting the Anaplasmataceae 16S
rRNA gene (16S). Positive samples were further evaluated, targeting a larger 16S
fragment, groEL operon, and gltA gene, followed by sequencing and phylogenetic
analysis. Anaplasmataceae DNA was detected in 15% (five of 33) of the tested
rodents (Abrothrix sp. [four of five] and Mus musculus [one of five]). Analysis of
sequenced products based on the 16S gene revealed high similarity with “Ca.
Neoehrlichia mikurensis,” “Ca. Neoehrlichia lotoris” and “Ca. Neoehrlichia arcana”
(97.8%–98.6%). A lower similarity was observed with Candidatus Neoehrlichia groEL
(89.7%-92%) and gltA (79.5%–79.9%) loci. According to the 16SrRNA, groEL and gltA
phylogenetic analyses, two closely related genotypes of “Candidatus Neoehrlichia”
spp. from Chile were observed, which clustered together in a separate clade from
other species in this genus. This study suggests the presence of two genotypes of a
novel species of “Candidatus Neoehrlichia,” proposed as “Candidatus Neoehrlichia
chilensis,” circulating in rodents from Chile. This is the first report of “Ca. Neoehrlichia”
species in rodents from America
Mycobacterium avium subsp. paratuberculosis (MAP) causes a chronic intestinal infection mainly in... more Mycobacterium avium subsp. paratuberculosis (MAP) causes a chronic intestinal infection mainly in domestic and wild ruminants and is transmitted primarily by the fecal-oral route. Mycobacterium bovis (M. bovis) produces a chronic infection principally of the respiratory system. It affects most domestic mammals, wild species, and humans and is spread via the respiratory or oral route. It is important to note that M. bovis is considered a major zoonotic agent. The term coinfection refers to the coexistence of two or more infectious agents in the same host. The goal of the present study was to assess management factors that may favor coinfection with MAP and M. bovis in cattle at an individual level. A cross-sectional study was conducted including 366 cattle from 11 herds. Diagnostic information for both pathogens and individual characteristics of the animals and management practices applied on them was collected from each herd. The results indicated a set of variables being more frequent in the coinfected group of animals and mainly related with biosecurity measures. This study provided regionally based data that may be used to design future control plans for both cattle infections in southern Chile.
Ruminants are the principal host
for infection by Mycobacterium avium subsp.
paratuberculosis (Ma... more Ruminants are the principal host for infection by Mycobacterium avium subsp. paratuberculosis (Map), the cause of Johne’s disease. Based on studies of a Map-infected population of European rabbits (Oryctolagus cuniculus) in Scotland, lagomorphs as a broad taxonomic order were proposed as potential nonruminant reservoirs for Map. To determine whether a different lagomorph species may serve as a wildlife reservoir, we investigated Map infection in European hares (Lepus europaeus) sharing habitat with known Mapinfected dairy cattle in southern Chile. Fecal, mesenteric lymph node, and ileal samples were aseptically collected from 385 wild hares for liquid culture and real-time polymerase chain reaction identification of acid-fast isolates. All tissue samples were also acid-fast stained and examined microscopically. We isolated Map from at least one tissue from 48 hares (12.6%) and fecal samples from 16 hares (4.2%). No Map was found in tissues of eight of the fecalculture– positive hares. Histologically, all tissues from all hares were within normal limits, and no acid-fast organisms were observed in any sample. Active infection, implying amplification of the organism secondary to resultant disease, was not evident. With this report Map isolations on a population versus incidental detection have now been made from two lagomorph species. However, although the rabbit population studied in Scotland appears to function as a Map reservoir, the hares studied in Chile appear to be a dead-end host, serving only as potential mechanical vectors for the organism
Currently, the Chilean authority has implemented a
National Eradication Program for bovine tuber... more Currently, the Chilean authority has implemented a
National Eradication Program for bovine tuberculosis (bTB),
aimed at controlling and eradicating the disease in Chile. The
area under study has a low within-herd prevalence, has a relatively
low number of infected herds, and is one of the major
milk and beef producing areas in the country. However, so far,
no attempts at eradicating the disease have been successful. It
has been suggested that the diagnostic tests used were either
not sensitive or specific enough. In addition, previous studies
have shown that a great number of herds are infected with
Mycobacterium avium subsp. paratuberculosis (MAP). The
present study estimates the effect of MAP infection under field
conditions, on the diagnostic sensitivity and specificity of routine
tests in live animals for Mycobacterium bovis infection
diagnosis in cattle. In general, the estimations of test accuracy
observed an increase in the sensitivity and specificity on
MAP-infected animals for tuberculin test but observed a
decrease in the sensitivity of gamma interferon tests for
MAP-infected cattle. These results are different from those
of previous studies considering the role of MAP infection as
an interfering infection. More research is needed in order to
understand the complex interactions of the different
mycobacteria that can be found infecting production
The aim of the present study was to assess the performance of routinely used diagnostic tests to ... more The aim of the present study was to assess the performance of routinely used diagnostic tests to detect M. bovis infection in cattle populations with very low infection prevalence. A cross-sectional study was performed using 609 animals from 17 herds that were sampled for blood interferon, and tested with the caudal fold tuberculin test (CFT). It was planned that animals which showed CFT positive results were sent to the slaughterhouse for post mortem confirmation testing. However, not all the animals considered in the initial sampling were culled. Paired population proportions of positive results for the different diagnostic tools were compared. Apparent sensitivity and specificity was also estimated. Overall, intradermal tuberculin based diagnostics showed better performance in comparison to interferon based test, even though interferon was slightly more specific. From these results, it may be suggested that specific cut-off lines for interferon based techniques for certain areas with particular low bTB prevalence should be considered, as well as the modification of more specific antigens and the use of better combinations of PPDs if in vitro testing is intended must be taken into consideration. The uncertain role of interference bacteria that could be affecting the results of the in vitro analysis must be considered, and perhaps this could explain the apparent lack of consensus of the results obtained in Chile versus the ones obtained elsewhere. More studies must be performed in order to assess this issue
Caligus royercresseyi (Boxshall and Bravo, 2000) has been one of the greatest challenges for the ... more Caligus royercresseyi (Boxshall and Bravo, 2000) has been one of the greatest challenges for the salmon farming industry in Chile since 1997. A field study was carried out in four areas of Region X in the period 2006-2007 to obtain information about the efficacy of emamectin benzoate in the control of C. rogercresseyi in farmed Atlantic salmon (Salmo salar), one of the susceptible salmon species reared in Chile. The results obtained in this study show that the differences observed in the values of prevalence and abundance between the four areas in Region X were mainly caused by the oceanographic conditions and not as a consequence of the number of treatments with emamectin benzoate applied in the period of study, which on average ranged between 8 and 14 treatments by area.
Infectious pancreatic necrosis (IPN) is a widespread and economically devastating fish disease ca... more Infectious pancreatic necrosis (IPN) is a widespread and economically devastating fish disease caused by infection with a virus referred to as IPN virus (IPNv). In Chile, the disease is endemic and prevalent in both fresh-and saltwater farms affecting cultured salmonids, mainly Atlantic salmon. Here, we present the results of a retrospective cohort study of Atlantic salmon farms stocked between 2010 and 2013, aimed at quantifying the extent to which certain epidemiological factors influence the time interval between stocking and onset of IPN mortality (time to mortality, ttm) in marine farms. Six variables were retained in a final multivariable Cox proportional hazard model. Compared to the 2010 stocking year, ttm was shorter for salmon stocked in years 2012 (HR = 2.1; p = 0.005) and 2013 (HR = 4.3; p = 0.01). The number of salmon farms within a 10-km radius (HR = 1.07; p = 0.002), positive report of IPN in the previous production cycle (HR = 1.95; p = 0.006), three or more smolt batches (HR = 2.27; p < 0.001), and positive report of mortality attributable to BKD (HR = 2.02; p < 0.001) were also associated with low ttm; conversely, ttm was longer for farms that stocked heavier fish (HR = 0.94; p = 0.001). The results presented here were consistent with early studies of IPN epidemiology in Norway and Scotland. Some of the risk factors identified in this study also influenced the risk for other diseases, such as infectious salmon anemia, suggesting that implementation of selected management practices may help to mitigate the burden of important infectious diseases of salmon in Chile.
Lameness is one of the greatest infringements of welfare in dairy cows. The objective of this stu... more Lameness is one of the greatest infringements of welfare in dairy cows. The objective of this study was to investigate associations between milk yield and foot lesions causing lameness in Chilean dairy cattle with the hypothesis that if we can demonstrate that lameness reduces yield, and so income, from lame dairy cows then we have both economic and welfare arguments for reducing lameness in dairy cattle. For one year, all lame cows from seven farms with Holstein Friesian cattle were treated by their herdsmen. Herdsmen were trained by the researcher and a colour atlas was utilised to assist in diagnosis of lesions. All abnormalities on the foot and the suspected cause of lameness were recorded, and cattle were treated. A two-level hierarchical model with repeated monthly test-day yields within cows was used to investigate the impact of double sole (DS), sole ulcer (SU), white line disease (WLD), digital dermatitis (DD) and all 'other' causes of lameness on milk yield before and after treatment. There were 1,635 cows with complete data. Cattle with a DS were higher yielding than cattle that were never lame with a reduction in yield from four months before treatment. Cattle lame with DD were higher yielding than non-lame cattle before and after treatment. For all causes of lameness, yield increased the month after treatment. We conclude that lesions causing lameness reduced the milk yield of dairy cows in these seven herds in Chile. We discuss the current evidence base for prevention of lameness in dairy cows and hypothesise that rapid treatment is a feasible current approach to improve cow welfare immediately and probably reduce milk lost; more evidence for effective prevention is required.
Two systems for transporting live salmon (Salmo salar) were compared in terms of their effects on... more Two systems for transporting live salmon (Salmo salar) were compared in terms of their effects on blood variables, muscle pH and rigor index: an 'open system' well-boat with recirculated sea water at 13.5°C and a stocking density of 107 kg/m3 during an eight-hour journey, and a 'closed system' well-boat with water chilled from 16.7 to 2.1°C and a stocking density of 243.7 kg/m3 during a seven-hour journey. Groups of 10 fish were sampled at each of four stages: in cages at the farm, in the well-boat after loading, in the well-boat after the journey and before unloading, and in the processing plant after they were pumped from the resting cages. At each sampling, the fish were stunned and bled by gill cutting. Blood samples were taken to measure lactate, osmolality, chloride, sodium, cortisol and glucose, and their muscle pH and rigor index were measured at death and three hours later. In the open system well-boat, the initial muscle pH of the fish decreased at each successive stage, and at the final stage they had a significantly lower initial muscle pH and more rapid onset of rigor than the fish transported on the closed system well-boat. At the final stage all the blood variables except glucose were significantly affected in the fish transported on both types of well-boat.
The effects of commercial harvest, transport in wellboat and ante
mortem handling on stress rela... more The effects of commercial harvest, transport in wellboat and ante
mortem handling on stress related blood constituents in salmon (Salmo
salar) were evaluated. Ten fish were sampled at each of six stages: on farm;
after loading; after transport in wellboat; after unloading; after resting and
after pumping to the processing plant. Blood concentrations of cortisol,
glucose, lactate, sodium, chloride and osmolality were determined. The
results of this study indicate that one of the most stressful stages was during
pumping from the resting cages to the processing plant. The concentration
of all variables studied dropped following a 24 hour rest in the cages and
most of them, with the exception of glucose, were increased after the fish
were pumped through the pipes from the resting cages to the processing
plant. This confirms that the last handling procedure is the most stressful
of the stages studied during this commercial transport
The purpose of this study was to describe patterns of seroconversion to bovine leukaemia virus an... more The purpose of this study was to describe patterns of seroconversion to bovine leukaemia virus and to estimate the main parameters needed for future model building. A longitudinal study was carried out between February 1999 and November 2001 in seven commercial dairy farms in Argentina using 1535 lactating cows. Time-interval parameters were analysed using a parametric survival model with shared frailty, time until infection was analysed using a Bayesian interval-censoring survival model and the infection transmission parameter (b) was estimated by a generalized linear model. The reproduction ratio (R 0) was calculated. In total, 1000 cows tested positive and 494 tested negative. The predicted median age at infection was 4. 6 years for seroconverted cows. For infected herds, the proportion of positive calves was as high as for infected cows and showed a large proportion of infected breeding heifers. Peaks in the overall average incidence per season-year were observed during autumn and spring. Results reveal that the period around parturition is a high-risk period. Moreover, heavily infected herds seem to have an increased proportion of young stock infected. The overall b was estimated as 2. 9/year (95 % CI 1. 9-3. 7) and combined with a relatively long infectious period it resulted in a high reproductive ratio (R 0 =8. 9). Therefore, a high effectiveness of control measures needs to be achieved to eradicate the disease.
Bovine Leukemia virus (BLV) is a ubiquitous retrovirus that affects mainly cattle. Knowledge of t... more Bovine Leukemia virus (BLV) is a ubiquitous retrovirus that affects mainly cattle. Knowledge of the precise moment of infection is fundamental for identification and evaluation of factors related to BLV transmission. Systematic reviews and meta-analyses provide good evidence on the effects of medical interventions. The objectives were to estimate time to sero-conversion after experimental infection using data from retrieved literature and to detect factors that may influence the length of that interval using survival analysis on pooled data. An analysis using aggregate data from 36 studies totalling 438 observations was performed. From this, four sets were created and analysed by interval-censored accelerated failure time models (AFT) with different distributions (exponential, Weibull, log-logistic, lognormal and generalized gamma), and some variants of the Cox model (Andersen-Gill, smoothing splines) with and without a frailty effect. The AFT gamma model fit best and the estimated median time to sero-conversion in the null model was 57 days (95% confidence interval (CI): 49; 75) using all data and 47 days (95% CI: 39; 55) when only studies using experimental inoculation were considered. Some factors were consistently associated with time to sero-conversion. These included exposure by animal-to-animal contact (resulting in a seven-fold increase in time to sero-conversion compared to direct inoculation), diagnostic method to detect sero-conversion (time to sero-conversion was 1.4 times shorter when AGID was used compared to ELISA), and transmission by insect bites (biological media) delayed sero-conversion 2.3 times compared transmission via needles or other inanimate media. www.elsevier.com/locate/prevetmed Preventive Veterinary Medicine 68 (2005) 241-262 After fitting a frailty Cox model, results showed that sero-conversion in susceptible animals after infection using donors, in which presence of virus before the experiment started was confirmed, increased the hazard of sero-conversion two times in comparison with donors in which virus presence was not confirmed before start of the experiment. Inoculation with blood decreased the hazard 2.5 times in comparison with lymphocyte suspensions. Heterogeneity due to different research groups was also present. Finally, a Cox model with smoothing splines contained three variables: research group, route of inoculation and a non-linear spline for infective dose. In conclusion, it can be stated some factors that influence the time to sero-conversion were identified and quantified and that a moderate influence of research centre existed. These results may contribute to the estimation of the most probable times of infection in field conditions and in a better evaluation of control measures. #
Journal of the Veterinary Diagnostic Investigation, 2005
The objective of this study was to validate a new blocking enzyme-linked immunosorbent assay (ELI... more The objective of this study was to validate a new blocking enzyme-linked immunosorbent assay (ELISA) (designated M108 for milk and S108 for serum samples) for detecting bovine leukemia virus (BLV) infection in dairy cattle. Milk, serum, and ethylenediaminetetraacetic acid-blood samples were collected from 524 adult Holstein cows originating from 6 dairy herds in Central Argentina. The M108 and S108 were compared with agar gel immunodiffusion (AGID), polymerase chain reaction and a commercial ELISA. Because there is currently no reference test capable of serving as a gold standard, the test sensitivity (SE) and specificity (SP) were evaluated by the use of a latent class model. Statistical inference was performed by classical maximum likelihood and by Bayesian techniques. The maximum-likelihood analysis was performed assuming conditional independence of tests, whereas the Bayesian approach allowed for conditional dependence. No clear conclusion could be drawn about conditional dependence of tests. Results with maximum likelihood (under conditional independence) and posterior Bayes (under conditional dependence) were practically the same. Conservative estimates of SE and SP (with 95% confidence intervals) for M108 were 98.6 (96.7; 99.6) and 96.7 (92.9; 98.8) and for S108 99.5 (98.2; 99.9) and 95.4 (90.9; 98.1), respectively. The ELISA 108 using either milk or serum to detect BLV-infected animals had comparable SE and SP with the official AGID and a commercial ELISA test, which are currently the most widely accepted tests for the serological diagnosis of BLV infection. Therefore , ELISA 108 can be used as an alternative test in monitoring and control programs.
Effective tools for use in control programmes against bovine leukaemia virus (BLV) infections req... more Effective tools for use in control programmes against bovine leukaemia virus (BLV) infections require insight into the relationship between the variant structure of the bovine leukaemia virus and the spatial-temporal interaction of isolates and hosts. Our study showed the presence of two types of BLV isolates-Australian and Argentine-in dairy herds from various parts of Central Argentina; these isolates were characterised by RFLP on PCR amplicons, and some of them were confirmed by sequencing. One genotype (Argentine) was present in all herds, and the Australian genotype was found in two herds. Phylogenetic analysis indicated four clusters. The first cluster was composed of the Argentine isolates and one from Brazil; the second was composed of several isolates found in European countries and one from Brazil; the third cluster was composed of BLV isolates found in Japan and Germany; the fourth cluster included American and Australian isolates and those from other countries. The comparison of a number of synonymous and non-synonymous nucleotide substitutions using various BLV genes revealed purifying selection, suggesting that molecular evolution occurred under some functional constraint.
The objectives of this study were to estimate herd and within-herd seroprevalences against bovine... more The objectives of this study were to estimate herd and within-herd seroprevalences against bovine leukemia virus in dairy herds of Región de los Ríos and Los Lagos, and to describe them according to the characteristics of the farm. A cross-sectional study and a random stratified sampling strategy were used. 4,360 blood and serum samples from females older than 6 month and bulls were collected from 75 dairy herds from September to December 2007, and they were processed using a commercial ELISA according to the instructions of the manufacturer. An overall proportion of infected herds (PIH) over total and the apparent prevalence (AP) were estimated by herd size and age group. Overall PIH was 34.7% (CI 95% (22.6; 44.1)) and 23.9% (CI 95% (11.1; 36.7)) for small herds, 43.5% (CI 95% (21.6; 65.4)) for median and 83.3% (CI 95% (40.5; 100.0)) for large herds and the difference was statistically significant (P < 0.05). General AP was 14.6% and the average AP was 5.3% (CI 95% (2.3; 8.3)). Average within-herd AP was 2.1% (CI 95% (0.34; 3.8)) for small herds, 10.13% (CI 95% (10.0; 10.2)) for median and 30.1% (CI 95% (29.9; 30.3)) for large herds and the difference was statistically significant (P < 0.05). The average AP for adults was 5.1% (CI 95% (1.6; 8.6)) and 1.3% (CI 95% (0.4; 2.2)) for young stock. The results suggest that in the area of study, large herds should be the target group for a control programme and the current situation might represent a business opportunity for small farmers by enrolling in a free certification scheme. Palabras clave: bovino, leucosis enzoótica, prevalencia, Chile.
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physical examination. The examination showed no abnormalities; therefore, complementary exams were performed. Leukocytosis with neutrophilia, monocytosis and hyperproteinaemia were detected. The urine analysis showed a bacterial infection without ultrasound findings. Serological titers to Leptospira interrogans serovar Pomona and Autumnalis were detected. Molecular analysis demonstrated the presence of Leptospira spp. in urine. The findings were consistent with subclinical leptospirosis. The cattle herd had evidence of Leptospira infection. The microbiological exams confirmed the presence of the Leptospira spp. in urine and serum. According to the evidence presented in this study, cats that dwell within a dairy farm could play a role in the
Leptospira infection epidemiologically. The importance of feline leptospirosis must be evaluated with leptospirosis control in livestock
The aims of this study were to identify factors associated with this disease
described in different observational studies and to combine the coinciding factors
in at least four studies using meta-analyses, to obtain a pooled odds ratio (OR) as
measure of infection risk. A literature search was performed in electronic databases,
electronic databases of specific journals and search engines to find studies
published in English, Spanish and Portuguese available from January 1960 to January
2015. Two hundred and eighteen factors were identified in 31 publications
including cross-sectional and case–control studies. Finally, independent metaanalyses
were performed with six different variables, which included between 4
and 8 articles. The pooled OR indicated that the variables ‘mixed-breed dogs’,
‘flooding occurrence in the habitat of the dog’ and ‘working dogs’ were risk
factors for leptospirosis, while ‘being a dog less than 1 year old’ was a protective
factor; however, all these associations were not statistically significant. Otherwise,
the variables ‘male dog’ and ‘urban dog’ were statistically significant risk factors
for infection. This study highlights the need for more formal studies on the epidemiology
of canine leptospirosis. Nevertheless, the study revealed that some risk
factors for infection coincided in different observational studies. These factors
could be considered to raise suspicion about the disease, especially when there is
a history of exposure to the bacteria
cross-sectional study was conducted in urban and rural environments in southern Chile
(1) to detect domestic cats with serologic evidence of exposure to Leptospira spp.; (2) to
determine the prevalence of anti-Leptospira antibodies; (3) to describe seroprevalences
according to different characteristics of the animals, and (4) to identify risk factors
associated with the seropositivity in the Microscopic Agglutination Test (MAT). Blood
samples were taken from 124 owned cats. A frequentist and Bayesian approach were
applied for prevalence estimation. The overall apparent prevalence of anti-Leptospira antibodies was 8.1% (95% Confident Interval = 3.9–4.3). With the Bayesian approach, the
overall True Prevalence (TP) was 5.2% (95% Credibility Interval (CrI) = 0.6–12.4). The
TP for urban cats was 1.8% (95% CrI = 0.1–7.2) and the TP for rural felines was 25.2%
(95% CrI = 9.3–46.6). Cats that live in a place where agricultural activities are performed
with water that flows in streams or backwater and cats that live in places near flooded areas
had a higher risk of seropositivity in MAT. The exposure to Leptospira spp. in domestic
cats of urban and rural origin in Southern Chile is a public health concern that requires an
increased awareness and the implementation of preventive measures
Methods: A prospective study among owned domestic dogs from southern Chile was performed by the Microscopic Agglutination Test: 1) to estimate
the rate of serological conversion for anti-Leptospira antibodies in a 6 to 9 month follow-up period, 2) to determine the reactive serovars and, 3) to measure
antibody titers in seropositive dogs. There were two samplings: in the first, 192 animals were sampled and 50 re-sampled dogs constituted the second.
Results: The rate of serological conversion in the follow-up period was 12.0% (95% Confidence Interval=2.9-21.0%). In the first sampling, the most
reactive serovars were Ballum and Canicola. In the second sampling, the most reactive serovar was Icterohaemorragiae. In both samplings, the antibody titers
ranged between 1:100 and 1:800, with predominance titers of 1:100 and 1:200.
Conclusions: The relatively high rate of serological conversion suggests that the exposure to Leptospira in dogs is present in southern Chile, with a possible
endemic presentation of the seropositivity. Preventive measures such as vaccination and to reduce the exposition of pet dogs to reservoirs of the bacteria must
be taken, as well to increase the awareness about Leptospira infection among public health institutions, veterinary practitioners and dog owners.
serovars that may be sheed in the urine of infected animals creating a highly infectious source of transmission. Numerous species of wild and domestic
mammals act as maintenance hosts and form reservoirs of the bacteria, with other species being incidental hosts that may develop the disease. In dogs
and cats, the disease is caused by different serovars and while dogs act as maintenance host for some serovars, both species are incidental host for
others. Dogs and cats may have frequent contact with wild and domestic farm animals, therefore they are an important link in the transmission route.
Leptospira may survive in the environment which increases the complexity of the epidemiology. The presentation of the disease can be highly variable
and, particularly for feline leptospirosis, not well described. Laboratory testing is essential for the diagnosis, however, it is complicated due to the need
to discriminate between Leptospira infection in animals with clinical disease from leptospiral specific antibody responses in maintenance hosts, or in
animals with subclinical infection. Infection in pets may have important economic and public health implications and because of the risk of transmission
from pets to their owners and to other animals, preventive measures need to be applied and an increased awareness is adviced
The Microscopic Agglutination Test (MAT) was used as reference assay. Anti-Leptospira
antibodies were detected in 37.3% of the dogs with MAT. Using the immunochromatography test, specific IgM antibodies were found in 13.1% of sampled dogs. The sensitivity of the rapid test as screening assay was 29.7% (95% Confidence Interval=16.4-47.2) and the specificity was 96.7% (95% Confidence Interval=87.8-99.4). 40.0% of the canines with clinical suspicion of leptospirosis and 37.1% of dogs without clinical signs were serological reactors to MAT, but none of MAT reactive dogs with clinical suspicion tested positive in the rapid test. Rapid and user-friendly diagnostic procedures for canine leptospirosis such as this immunochromatography assay could be important tools to use in clinical practice, however, further studies are needed to obtain more information about their utility, considering that diagnostic tests could not have similar performances in different geographic locations, clinical and epidemiological contexts
Anaplasmatacea. Spleen samples from 33 wild rodents trapped in Valdivia Province
were screened by conventional PCR (cPCR), targeting the Anaplasmataceae 16S
rRNA gene (16S). Positive samples were further evaluated, targeting a larger 16S
fragment, groEL operon, and gltA gene, followed by sequencing and phylogenetic
analysis. Anaplasmataceae DNA was detected in 15% (five of 33) of the tested
rodents (Abrothrix sp. [four of five] and Mus musculus [one of five]). Analysis of
sequenced products based on the 16S gene revealed high similarity with “Ca.
Neoehrlichia mikurensis,” “Ca. Neoehrlichia lotoris” and “Ca. Neoehrlichia arcana”
(97.8%–98.6%). A lower similarity was observed with Candidatus Neoehrlichia groEL
(89.7%-92%) and gltA (79.5%–79.9%) loci. According to the 16SrRNA, groEL and gltA
phylogenetic analyses, two closely related genotypes of “Candidatus Neoehrlichia”
spp. from Chile were observed, which clustered together in a separate clade from
other species in this genus. This study suggests the presence of two genotypes of a
novel species of “Candidatus Neoehrlichia,” proposed as “Candidatus Neoehrlichia
chilensis,” circulating in rodents from Chile. This is the first report of “Ca. Neoehrlichia”
species in rodents from America
for infection by Mycobacterium avium subsp.
paratuberculosis (Map), the cause of Johne’s
disease. Based on studies of a Map-infected
population of European rabbits (Oryctolagus
cuniculus) in Scotland, lagomorphs as a broad
taxonomic order were proposed as potential
nonruminant reservoirs for Map. To determine
whether a different lagomorph species may
serve as a wildlife reservoir, we investigated
Map infection in European hares (Lepus
europaeus) sharing habitat with known Mapinfected
dairy cattle in southern Chile. Fecal,
mesenteric lymph node, and ileal samples were
aseptically collected from 385 wild hares for
liquid culture and real-time polymerase chain
reaction identification of acid-fast isolates. All
tissue samples were also acid-fast stained and
examined microscopically. We isolated Map
from at least one tissue from 48 hares (12.6%)
and fecal samples from 16 hares (4.2%). No
Map was found in tissues of eight of the fecalculture–
positive hares. Histologically, all tissues
from all hares were within normal limits, and no
acid-fast organisms were observed in any
sample. Active infection, implying amplification
of the organism secondary to resultant disease,
was not evident. With this report Map isolations
on a population versus incidental detection
have now been made from two lagomorph
species. However, although the rabbit population
studied in Scotland appears to function as a
Map reservoir, the hares studied in Chile
appear to be a dead-end host, serving only as
potential mechanical vectors for the organism
National Eradication Program for bovine tuberculosis (bTB),
aimed at controlling and eradicating the disease in Chile. The
area under study has a low within-herd prevalence, has a relatively
low number of infected herds, and is one of the major
milk and beef producing areas in the country. However, so far,
no attempts at eradicating the disease have been successful. It
has been suggested that the diagnostic tests used were either
not sensitive or specific enough. In addition, previous studies
have shown that a great number of herds are infected with
Mycobacterium avium subsp. paratuberculosis (MAP). The
present study estimates the effect of MAP infection under field
conditions, on the diagnostic sensitivity and specificity of routine
tests in live animals for Mycobacterium bovis infection
diagnosis in cattle. In general, the estimations of test accuracy
observed an increase in the sensitivity and specificity on
MAP-infected animals for tuberculin test but observed a
decrease in the sensitivity of gamma interferon tests for
MAP-infected cattle. These results are different from those
of previous studies considering the role of MAP infection as
an interfering infection. More research is needed in order to
understand the complex interactions of the different
mycobacteria that can be found infecting production
mortem handling on stress related blood constituents in salmon (Salmo
salar) were evaluated. Ten fish were sampled at each of six stages: on farm;
after loading; after transport in wellboat; after unloading; after resting and
after pumping to the processing plant. Blood concentrations of cortisol,
glucose, lactate, sodium, chloride and osmolality were determined. The
results of this study indicate that one of the most stressful stages was during
pumping from the resting cages to the processing plant. The concentration
of all variables studied dropped following a 24 hour rest in the cages and
most of them, with the exception of glucose, were increased after the fish
were pumped through the pipes from the resting cages to the processing
plant. This confirms that the last handling procedure is the most stressful
of the stages studied during this commercial transport