Puffy skin disease (PSD) is a disease that causes skin pathology in rainbow trout, Oncorhynchus m... more Puffy skin disease (PSD) is a disease that causes skin pathology in rainbow trout, Oncorhynchus mykiss (Walbaum). Incidence of PSD in UK fish farms and fisheries has increased sharply in the last decade, with growing concern from both industry sectors. This paper provides the first comprehensive case definition of PSD, combining clinical and pathological observations of diseased rainbow trout from both fish farms and fisheries. The defining features of PSD, as summarized in the case definition, were focal lateral flank skin lesions that appeared as cutaneous swelling with pigment loss and petechiae. These were associated with lethargy, poor body condition, inappetance and low level mortality. Epidermal hyperplasia and spongiosis, oedema of the dermis stratum spongiosum and a mild diffuse inflammatory cellularity were typical in histopathology of skin. A specific pathogen or aetiology was not identified. Prevalence and severity of skin lesions was greatest during late summer and autumn, with the highest prevalence being 95%. Atypical lesions seen in winter and spring were suggestive of clinical resolution. PSD holds important implications for both trout aquaculture and still water trout fisheries. This case definition will aid future diagnosis, help avoid confusion with other skin conditions and promote prompt and consistent reporting.
Hafnia alvei was isolated in Bulgaria from healthy noble crayfish, Astacus astacus (L.), and then... more Hafnia alvei was isolated in Bulgaria from healthy noble crayfish, Astacus astacus (L.), and then from farmed diseased brown trout, Salmo trutta L., with signs of haemorrhagic septicaemia. The isolates were identified initially with conventional phenotyping and commercial Merlin Micronaut and API 20E rapid identification systems, followed by sequencing of the 16S rRNA gene. Hafnia alvei Bt1, Bt2 and Aa4 were of low virulence to rainbow trout and brown trout, although cytotoxicity was demonstrated by Bt1 and Bt2, but not by Aa4.
Captive snakes, that is, a Jamaican boa (Epicrates subflavus) a yellow anaconda (Eunectes notaeus... more Captive snakes, that is, a Jamaican boa (Epicrates subflavus) a yellow anaconda (Eunectes notaeus) and a corn snake (Pantherophis guttatus guttatus), died with signs of bacteraemia including the presence of petechial haemorrhages in the mouth and gums and haemorrhages in the lung, spleen and intestines. The abdomen and anus were swollen with bloody-tinged mucus in the colon. Aeromonas hydrophila was recovered in dense virtually pure culture growth from the internal organs. Characterization of the isolates was by phenotyping and sequencing of the 16S rRNA gene (sequence homology of 99% with A. hydrophila) with outputs confirming the identity as A. hydrophila. Pathogenicity experiments confirmed virulence to frogs (Rana esculenta) and rainbow trout (Oncorhynchus mykiss).
Streptococcus agalactiae infections in fish are predominantly caused by beta-haemolytic strains o... more Streptococcus agalactiae infections in fish are predominantly caused by beta-haemolytic strains of clonal complex (CC) 7, notably its namesake sequence type (ST) 7, or by non-haemolytic strains of CC552, including the globally distributed ST260. In contrast, CC23, including its namesake ST23, has been associated with a wide homeothermic and poikilothermic host range, but never with fish. The aim of this study was to determine whether ST23 is virulent in fish and to identify genomic markers of fish adaptation of S. agalactiae. Intraperitoneal challenge of Nile tilapia, Oreochromis niloticus (Linnaeus), showed that ST260 is lethal at doses down to 10(2 ) cfu per fish, whereas ST23 does not cause disease at 10(7 ) cfu per fish. Comparison of the genome sequence of ST260 and ST23 with those of strains derived from fish, cattle and humans revealed the presence of genomic elements that are unique to subpopulations of S. agalactiae that have the ability to infect fish (CC7 and CC552). Thes...
Rainbow trout gastroenteritis (RTGE) is an emerging syndrome linked to the presence of large numb... more Rainbow trout gastroenteritis (RTGE) is an emerging syndrome linked to the presence of large numbers of the segmented filamentous bacterium "Candidatus arthromitus" within the intestine. The present study examined the histopathological changes of the digestive tract of 152 trout with gross lesions typical of RTGE. Histopathology showed that 129 of 152 fish (85%) affected with RTGE had segmented filamentous bacteria in the distal intestine and/or pyloric caeca. The presence and number of segmented filamentous bacteria were always significantly higher (P < .001) in pyloric caeca, thereby suggesting the preferred site for these bacteria. Histopathological changes included enterocyte detachment and congestion of the lamina propria and adventitial layers. Samples from 6 RTGE-affected trout were examined using scanning and transmission electron microscopy, revealing a close interaction of segmented filamentous bacteria with the mucosa of distal intestine and pyloric caeca, with the presence of bacterial attachment sites, and with associated morphological changes of the apical membrane of enterocytes. Despite these interactions, segmented filamentous bacteria were not always adjacent to the areas with pathological changes, suggesting that if these organisms play a role in the pathogenesis of RTGE, extracellular products may be involved. Ultrastructural changes included loss of microvillar structure, membrane blebbing, hydropic mitochondrial damage, and basal hydropic degeneration of enterocytes, which frequently resulted in disruption of tight junctions and enterocyte detachment. The resulting exposure of large areas of lamina propria probably resulted in the compromise of the host osmotic balance and the facilitation of the entry of secondary pathogens.
... link, especially as the DNA primers are very species specific (Toyama and others 1994) and th... more ... link, especially as the DNA primers are very species specific (Toyama and others 1994) and the results from the Scottish samples were ... F psychrophilum is known to favour connective tis-sues (Madsen and Dalsgaard 1998, Ostland and others 2000); presumably the tissue ...
Rainbow trout gastroenteritis (RTGE) is an emerging disease of farmed rainbow trout (Oncorhynchus... more Rainbow trout gastroenteritis (RTGE) is an emerging disease of farmed rainbow trout (Oncorhynchus mykiss) reported in Croatia, France, Italy, Spain and the UK. The impact of RTGE at the site-level varies, and daily mortalities of 0.5-1% are common. Gross lesions include severe enteritis with congestion and oedema, and the segmented filamentous bacterium "Candidatus arthromitus" has been suggested as a possible aetiological agent. This paper presents findings from a prospective longitudinal epidemiology study that took place from June to November 2006 in 12 RTGE-positive UK sites, examining the impact and presentation of the disease, spread pattern, risk factors for disease presence and severity and the efficacy of current control strategies. RTGE was present in a total of 164 production units across the 12 sites, representing 39% of all stocked units. Fish losses due to RTGE totalled 61.4tonnes. The plotting of epidemic curves revealed a propagating epidemic pattern in 51% affected units, suggesting RTGE is infectious. This was supported by risk analysis of fish transfers and site layouts, which revealed an increased risk of becoming RTGE positive after contiguity or fish transfer to and from a previously affected unit. Conditional multivariate logistic regression analysis identified eight variables significantly associated with the presence of RTGE. Seven variables were risk factors, including higher stocking densities, mortalities due to predation or handling, higher water temperature, higher daily feed input and contiguity or fish movement to and from a previous case. One variable was protective: the absence of an aeration system in a unit. General linear modelling identified a significant association of mean feed input per fish during an outbreak with RTGE cumulative mortality. Finally, great variability was observed with regards to the control strategies targeted to RTGE in these sites, suggesting an absence of a common strategy. In feed NaCl treatments apparently presented a palliative effect if given to affected fish during the clinical outbreaks, but they did not prevent recurrence.
Journal of Veterinary Diagnostic Investigation, 2010
Swarms or blooms of jellyfish are increasingly problematic and can result in high mortality rates... more Swarms or blooms of jellyfish are increasingly problematic and can result in high mortality rates of farmed fish. Small species of jellyfish, such as Phialella quadrata (13 mm in diameter), are capable of passing through the mesh of sea cages and being sucked into the mouth of fish during respiration. Results of the current study show that the initial damage to gills of farmed Atlantic salmon, likely produced by nematocyst-derived toxins from the jellyfish, was compounded by secondary bacterial infection with Tenacibaculum maritimum. Results also demonstrate that these filamentous bacteria were present on the mouth of the jellyfish and that their DNA sequences were almost identical to those of bacteria present on the salmon gills. This suggests that the bacterial lesions were not the result of an opportunistic infection of damaged tissue, as previously thought. Instead, P. quadrata is probably acting as a vector for this particular bacterial pathogen, and it is the first time that evidence to support such a link has been presented. No prior literature describing the presence of bacteria associated with jellyfish, except studies about their decay, could be found. It is not known if all jellyfish of this and other species carry similar bacteria or the relationship to each other. Their source, the role they play under other circumstances, and indeed whether the jellyfish were themselves diseased are also not known. The high proteolytic capabilities of T. maritimum mean that partially digested gill tissues were readily available to the jellyfish, which rely heavily on intracellular digestion for their nutrition.
This is the first description of an economically important disease of intensively reared Pangasiu... more This is the first description of an economically important disease of intensively reared Pangasius hypophthalmus from the Mekong Delta. Major presenting signs included an increase in mortality that would not respond to treatment, and at necropsy, the presence of ...
Puffy skin disease (PSD) is a disease that causes skin pathology in rainbow trout, Oncorhynchus m... more Puffy skin disease (PSD) is a disease that causes skin pathology in rainbow trout, Oncorhynchus mykiss (Walbaum). Incidence of PSD in UK fish farms and fisheries has increased sharply in the last decade, with growing concern from both industry sectors. This paper provides the first comprehensive case definition of PSD, combining clinical and pathological observations of diseased rainbow trout from both fish farms and fisheries. The defining features of PSD, as summarized in the case definition, were focal lateral flank skin lesions that appeared as cutaneous swelling with pigment loss and petechiae. These were associated with lethargy, poor body condition, inappetance and low level mortality. Epidermal hyperplasia and spongiosis, oedema of the dermis stratum spongiosum and a mild diffuse inflammatory cellularity were typical in histopathology of skin. A specific pathogen or aetiology was not identified. Prevalence and severity of skin lesions was greatest during late summer and autumn, with the highest prevalence being 95%. Atypical lesions seen in winter and spring were suggestive of clinical resolution. PSD holds important implications for both trout aquaculture and still water trout fisheries. This case definition will aid future diagnosis, help avoid confusion with other skin conditions and promote prompt and consistent reporting.
Hafnia alvei was isolated in Bulgaria from healthy noble crayfish, Astacus astacus (L.), and then... more Hafnia alvei was isolated in Bulgaria from healthy noble crayfish, Astacus astacus (L.), and then from farmed diseased brown trout, Salmo trutta L., with signs of haemorrhagic septicaemia. The isolates were identified initially with conventional phenotyping and commercial Merlin Micronaut and API 20E rapid identification systems, followed by sequencing of the 16S rRNA gene. Hafnia alvei Bt1, Bt2 and Aa4 were of low virulence to rainbow trout and brown trout, although cytotoxicity was demonstrated by Bt1 and Bt2, but not by Aa4.
Captive snakes, that is, a Jamaican boa (Epicrates subflavus) a yellow anaconda (Eunectes notaeus... more Captive snakes, that is, a Jamaican boa (Epicrates subflavus) a yellow anaconda (Eunectes notaeus) and a corn snake (Pantherophis guttatus guttatus), died with signs of bacteraemia including the presence of petechial haemorrhages in the mouth and gums and haemorrhages in the lung, spleen and intestines. The abdomen and anus were swollen with bloody-tinged mucus in the colon. Aeromonas hydrophila was recovered in dense virtually pure culture growth from the internal organs. Characterization of the isolates was by phenotyping and sequencing of the 16S rRNA gene (sequence homology of 99% with A. hydrophila) with outputs confirming the identity as A. hydrophila. Pathogenicity experiments confirmed virulence to frogs (Rana esculenta) and rainbow trout (Oncorhynchus mykiss).
Streptococcus agalactiae infections in fish are predominantly caused by beta-haemolytic strains o... more Streptococcus agalactiae infections in fish are predominantly caused by beta-haemolytic strains of clonal complex (CC) 7, notably its namesake sequence type (ST) 7, or by non-haemolytic strains of CC552, including the globally distributed ST260. In contrast, CC23, including its namesake ST23, has been associated with a wide homeothermic and poikilothermic host range, but never with fish. The aim of this study was to determine whether ST23 is virulent in fish and to identify genomic markers of fish adaptation of S. agalactiae. Intraperitoneal challenge of Nile tilapia, Oreochromis niloticus (Linnaeus), showed that ST260 is lethal at doses down to 10(2 ) cfu per fish, whereas ST23 does not cause disease at 10(7 ) cfu per fish. Comparison of the genome sequence of ST260 and ST23 with those of strains derived from fish, cattle and humans revealed the presence of genomic elements that are unique to subpopulations of S. agalactiae that have the ability to infect fish (CC7 and CC552). Thes...
Rainbow trout gastroenteritis (RTGE) is an emerging syndrome linked to the presence of large numb... more Rainbow trout gastroenteritis (RTGE) is an emerging syndrome linked to the presence of large numbers of the segmented filamentous bacterium "Candidatus arthromitus" within the intestine. The present study examined the histopathological changes of the digestive tract of 152 trout with gross lesions typical of RTGE. Histopathology showed that 129 of 152 fish (85%) affected with RTGE had segmented filamentous bacteria in the distal intestine and/or pyloric caeca. The presence and number of segmented filamentous bacteria were always significantly higher (P < .001) in pyloric caeca, thereby suggesting the preferred site for these bacteria. Histopathological changes included enterocyte detachment and congestion of the lamina propria and adventitial layers. Samples from 6 RTGE-affected trout were examined using scanning and transmission electron microscopy, revealing a close interaction of segmented filamentous bacteria with the mucosa of distal intestine and pyloric caeca, with the presence of bacterial attachment sites, and with associated morphological changes of the apical membrane of enterocytes. Despite these interactions, segmented filamentous bacteria were not always adjacent to the areas with pathological changes, suggesting that if these organisms play a role in the pathogenesis of RTGE, extracellular products may be involved. Ultrastructural changes included loss of microvillar structure, membrane blebbing, hydropic mitochondrial damage, and basal hydropic degeneration of enterocytes, which frequently resulted in disruption of tight junctions and enterocyte detachment. The resulting exposure of large areas of lamina propria probably resulted in the compromise of the host osmotic balance and the facilitation of the entry of secondary pathogens.
... link, especially as the DNA primers are very species specific (Toyama and others 1994) and th... more ... link, especially as the DNA primers are very species specific (Toyama and others 1994) and the results from the Scottish samples were ... F psychrophilum is known to favour connective tis-sues (Madsen and Dalsgaard 1998, Ostland and others 2000); presumably the tissue ...
Rainbow trout gastroenteritis (RTGE) is an emerging disease of farmed rainbow trout (Oncorhynchus... more Rainbow trout gastroenteritis (RTGE) is an emerging disease of farmed rainbow trout (Oncorhynchus mykiss) reported in Croatia, France, Italy, Spain and the UK. The impact of RTGE at the site-level varies, and daily mortalities of 0.5-1% are common. Gross lesions include severe enteritis with congestion and oedema, and the segmented filamentous bacterium "Candidatus arthromitus" has been suggested as a possible aetiological agent. This paper presents findings from a prospective longitudinal epidemiology study that took place from June to November 2006 in 12 RTGE-positive UK sites, examining the impact and presentation of the disease, spread pattern, risk factors for disease presence and severity and the efficacy of current control strategies. RTGE was present in a total of 164 production units across the 12 sites, representing 39% of all stocked units. Fish losses due to RTGE totalled 61.4tonnes. The plotting of epidemic curves revealed a propagating epidemic pattern in 51% affected units, suggesting RTGE is infectious. This was supported by risk analysis of fish transfers and site layouts, which revealed an increased risk of becoming RTGE positive after contiguity or fish transfer to and from a previously affected unit. Conditional multivariate logistic regression analysis identified eight variables significantly associated with the presence of RTGE. Seven variables were risk factors, including higher stocking densities, mortalities due to predation or handling, higher water temperature, higher daily feed input and contiguity or fish movement to and from a previous case. One variable was protective: the absence of an aeration system in a unit. General linear modelling identified a significant association of mean feed input per fish during an outbreak with RTGE cumulative mortality. Finally, great variability was observed with regards to the control strategies targeted to RTGE in these sites, suggesting an absence of a common strategy. In feed NaCl treatments apparently presented a palliative effect if given to affected fish during the clinical outbreaks, but they did not prevent recurrence.
Journal of Veterinary Diagnostic Investigation, 2010
Swarms or blooms of jellyfish are increasingly problematic and can result in high mortality rates... more Swarms or blooms of jellyfish are increasingly problematic and can result in high mortality rates of farmed fish. Small species of jellyfish, such as Phialella quadrata (13 mm in diameter), are capable of passing through the mesh of sea cages and being sucked into the mouth of fish during respiration. Results of the current study show that the initial damage to gills of farmed Atlantic salmon, likely produced by nematocyst-derived toxins from the jellyfish, was compounded by secondary bacterial infection with Tenacibaculum maritimum. Results also demonstrate that these filamentous bacteria were present on the mouth of the jellyfish and that their DNA sequences were almost identical to those of bacteria present on the salmon gills. This suggests that the bacterial lesions were not the result of an opportunistic infection of damaged tissue, as previously thought. Instead, P. quadrata is probably acting as a vector for this particular bacterial pathogen, and it is the first time that evidence to support such a link has been presented. No prior literature describing the presence of bacteria associated with jellyfish, except studies about their decay, could be found. It is not known if all jellyfish of this and other species carry similar bacteria or the relationship to each other. Their source, the role they play under other circumstances, and indeed whether the jellyfish were themselves diseased are also not known. The high proteolytic capabilities of T. maritimum mean that partially digested gill tissues were readily available to the jellyfish, which rely heavily on intracellular digestion for their nutrition.
This is the first description of an economically important disease of intensively reared Pangasiu... more This is the first description of an economically important disease of intensively reared Pangasius hypophthalmus from the Mekong Delta. Major presenting signs included an increase in mortality that would not respond to treatment, and at necropsy, the presence of ...
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Papers by M. Crumlish