Cardiac abnormality with associated hernia in farmed rainbow trout Oncorhynchus mykiss. (57/711)

A new type of cardiac malformation in rainbow trout Oncorhynchus mykiss from a broodstock fish farm is described. The ventricle of affected fish was located dorsodextrally to the atrium, while the latter was saccular, grossly enlarged and protruded through the muscles of the ventral body wall, forming a hernia covered only by dermis and epidermis. Histopathological changes included hypoplasia of the outer compact layer of the ventricular myocardium and severe distension of trabecular structures within the ventricle and atrium. Affected fish tolerated stress very poorly, and the majority of the affected fish died during the freshwater period. The causation(s) are not known, but hereditary and environmental factors are likely, as no infectious agents were isolated or detected microscopically.  (+info)

Pathological changes in juvenile Atlantic halibut Hippoglossus hippoglossus persistently infected with nodavirus. (58/711)

This is the first description of a persistent subclinical nodavirus infection in the Atlantic halibut Hippoglossus hippoglossus. Juvenile fish (1 to 5 g) were sampled at 4, 5 and 8 mo of age at a fish farm in Norway during and after weaning. None showed clinical signs of viral encephalopathy and retinopathy (VER) or other disease. Pathological changes and/or nodavirus were detected by light microscopy, immunohistochemistry, reverse transcriptase polymerase chain reaction (RT-PCR) and transmission electron microscopy in all fish examined. High numbers of virus particles were found in macrophage-like cells in the central nervous system, including brain and retina (CNS). The virus particles displayed the icosahedral shape and size (approximately 25 nm) characteristic of nodaviruses. The virus-infected cells formed focal cell aggregates and were seen in all regions of the brain and all nuclear cell layers of the retina. The cytoplasm of the infected cells was filled with membrane-enclosed inclusions packed with virus particles. Some virus particles lay along membranes and formed membrane-bound necklace-like arrangements. The virus-infected cells of the retina also contained pigment granula located generally inside virus inclusions and sometimes forming a coating around the virus particles. All frontal parts with the eyes and brain and 50% of the mid-parts, which included the abdominal organs, were found positive for nodavirus with RT-PCR. Pathological changes in these persistently nodavirus-infected fish differ from earlier descriptions in Atlantic halibut during outbreaks of VER. Vertical transmission from infected spawners is believed to be a major route for nodavirus infection. Detection of nodavirus in subclinical infected fish and a better understanding of its pathogenesis are important in order to prevent the spread of nodavirus in the fish-farming industry.  (+info)

Isolation of viral hemorrhagic septicemia virus from Greenland halibut Reinhardtius hippoglossoides caught at the Flemish Cap. (59/711)

Viral hemorrhagic septicemia virus (VHSV) was isolated from apparently healthy Greenland halibut Reinhardtius hippoglossoides caught in the Flemish Cap, a deep fishing ground in the North Atlantic Ocean in international waters near Newfoundland. The identity of the virus was confirmed by electron microscopy, immunodot, seroneutralization and reverse transcriptasepolymerase chain reaction. In the serology assays, all isolates reacted in the immunodot assay with a polyclonal antiserum against the European VHSV Type Strain F1, and were neutralized by the same antiserum, although most of the strains showed low or moderate neutralization titers. None of the isolates were detected by immunofluorescence using a specific monoclonal antibody against a nucleocapsid-related protein of VHSV F1. This is the first report of VHSV isolated from wild Greenland halibut, which represents a new host species for the virus, and it is also the first evidence of VHSV in a location close to the Atlantic coast of North America. This isolation indicates that VHSV is more widely distributed than has been thought, and appears to support a marine origin of this virus.  (+info)

Serological evidence of infectious salmon anaemia virus (ISAV) infection in farmed fishes, using an indirect enzyme-linked immunosorbent assay (ELISA). (60/711)

Antibody detection tests are rarely used for diagnostic purposes in fish diseases. Infectious salmon anaemia (ISA) caused by ISA virus (ISAV) is an emerging disease of Atlantic salmon Salmo salar L. The virus has also been isolated from diseased coho salmon Oncorhynchus kisutch in Chile. An indirect enzyme-linked immunosorbent assay (ELISA) that should facilitate serodiagnosis of ISAV infection, the study of epidemiology, and the control of ISA in farmed fishes has been developed using purified ISAV as the coating antigen, and monoclonal antibodies that detect fish immunoglobulins bound to the antigen on the plate. Application of the test to a random sample of farmed Atlantic salmon from the Bay of Fundy, New Brunswick, Canada, positively identified 5 of the 7 ISAV RT-PCR-positive fish, and all 10 RT-PCR-negative fish were also negative in the ELISA. Some RT-PCR-negative fish had an elevated non-specific antibody reactivity suggestive of chronic infection or resistance to ISAV. This test was also able to detect 11 of the 14 coho salmon pooled serum samples from a clinically affected farm in Chile that were positive by the virus neutralization (VN) test, and 2 of the 4 VN-negative samples. We conclude that this ELISA would be suitable as a routine test for ISAV infection or for assessing ISAV vaccine efficacy before placing smolts in sea cages, and for testing fishes in sea cages to detect level of resistance to ISA. The assay enables vaccination in combination with depopulation control methods.  (+info)

Clinical efficacy of teflubenzuron (Calicide) for the treatment of Lepeophtheirus salmonis infestations of farmed Atlantic salmon Salmo salar at low water temperatures. (61/711)

The efficacy of teflubenzuron (Calicide) for the treatment of farmed Atlantic salmon Salmo salar L. infested with sea lice Lepeophtheirus salmonis (Kroyer, 1838), was investigated at low water temperatures in 2 commercial salmon farms. Calicide, coated on commercial feed pellets, was administered orally at 10 mg kg(-1) d(-1) for 7 consecutive days. Fish were randomly sampled and lice numbers recorded from both treated and control groups on 3 or 4 sampling occasions post-medication. Statistically significant reductions in the number of L. salmonis per fish were recorded. Maximum efficacy was observed toward chalimus and preadult stages of L. salmonis, and was achieved approximately 26 d post-medication. No adverse drug reactions or palatability problems were associated with the treatments.  (+info)

Spinal deformities in farmed Atlantic salmon. (62/711)

Spinal deformities in farmed Atlantic salmon (Salmo salar) are often observed in intensive farming systems and result in production losses. Many putative factors have been implicated with the formation of spinal deformities in larger salmon. This condition has been described as broken back syndrome, curvy back disease, and short tails.  (+info)

Life-history correlates of maximum population growth rates in marine fishes. (63/711)

Theory predicts that populations of animals with late maturity, low fecundity, large body size and low body growth rates will have low potential rates of population increase at low abundance. If this is true, then these traits may be used to predict the intrinsic rate of increase for species or populations, as well as extinction risks. We used life-history and population data for 63 stocks of commercially exploited fish species from the northeast Atlantic to test relationships between life-history parameters and the rate of population increase at low abundance. We used cross-taxonomic analyses among stocks and among species, and analyses that accounted for phylogenetic relationships. These analyses confirmed that large-bodied, slow-growing stocks and species had significantly lower rates of recruitment and adult production per spawning adult at low abundance. Furthermore, high ages at maturity were significantly correlated with low maximum recruit production. Contrary to expectation, fecundity was significantly negatively related to recruit production, due to its positive relationship with maximum body size. Our results support theoretical predictions, and suggest that a simply measured life-history parameter can provide a useful tool for predicting rates of recovery from low population abundance.  (+info)

Impact of integrated fish farming on antimicrobial resistance in a pond environment. (64/711)

Integrated fish farming combines livestock production with fish farming. Animal manure is shed directly into a fish pond as fertilizer and supports the growth of photosynthetic organisms. The livestock, mainly chickens and pigs, is often fed feed containing growth promoters. In this study we investigated the impact of integrated fish farming on the levels of antimicrobial-resistant bacteria in a pond environment. One integrated broiler chicken-fish farm was studied for 2 months immediately after the start of a new fish production cycle. A significant increase over time in the resistance to six different antimicrobials was found for the indicator organism Acinetobacter spp. isolated from composite water-sediment samples. The initial resistance levels prior to the new production cycle were 1 to 5%. After 2 months the levels of resistance to oxytetracycline and sulfamethoxazole reached 100%, and the levels of resistance to ciprofloxacin were more than 80%. The long-term effects of resistance on integrated farming were studied on seven additional farms. The resistance levels were particularly high among Enterococcus spp. and were also high among Acinetobacter spp. isolated from water-sediment samples compared to the resistance levels at four control farms. In conclusion, integrated fish farming seems to favor antimicrobial-resistant bacteria in the pond environment. This could be attributed to the selective pressure of antimicrobials in the pond environment and/or to the introduction of antimicrobial-resistant bacteria from animal manure. Potential risks to human health were not addressed in this study and remain to be elucidated.  (+info)