Near-Complete Genome Sequence of Lötschberg Virus (Mononegavirales: Filoviridae) Identified in European Perch (Perca fluviatilis Linnaeus, 1758).

We obtained the near-complete genome sequence of a novel virus, Lötschberg virus (LTBV), from a European perch metatranscriptome. Genome organization and pairwise sequence comparison indicated that LTBV represents a tentative new species and genus of the mononegaviral family Filoviridae

Proliferative kidney disease (PKD) of rainbow trout: temperature- and time-related changes of Tetracapsuloides bryosalmonae DNA in the kidney

Proliferative kidney disease (PKD) of salmonids, caused by Tetracapsuloides bryosalmonae, can lead to high mortalities at elevated water temperature. We evaluated the hypothesis that this mortality is caused by increasing parasite intensity. T. bryosalmonae-infected rainbow trout (Oncorhynchus mykiss) were reared at different water temperatures and changes in parasite concentrations in the kidney were compared to cumulative mortalities. Results of parasite quantification by a newly developed real-time PCR agreed with the number of parasites detected by immunohistochemistry, except for very low or very high parasite loads because of heterogenous distribution of the parasites in the kidney. Two experiments were performed, where fish were exposed to temperatures of 12, 14, 16, 18 or 19°C after an initial exposure to an infectious environment at 12-16°C resulting in 100% prevalence of infected fish after 5 to 14 days of exposure. While mortalities differed significantly between all investigated water temperatures, significant differences in final parasite loads were only found between fish kept at 12°C and all other groups. Differences in parasite load between fish kept at 14°C to 19°C were not significant. These findings provide evidence that there is no direct link between parasite intensity and fish mortalit

Glomerulocystic kidney in two red piranhas Pygocentrus nattereri.

Glomerulocystic kidney (GCK) is defined by a dilatation of the Bowman's space (greater than 2 times the normal size) of more than 5% of all glomeruli. Although GCK has been occasionally documented in dogs, cats, and humans with renal failure, in fish, reports of spontaneous GCK are rare. For the present study, 2 captive adult red piranhas Pygocentrus nattereri from a closed population were submitted for post-mortem examination. Clinical history included lethargy, inappetence, dyspnea, and altered buoyancy. Macroscopically, the fish displayed coelomic distension and ascites. The kidneys were markedly enlarged and dark yellow. Histologically, Bowman's space was noticeably dilated, occasionally with atrophic glomerular tufts. Degeneration and necrosis of the tubular epithelium, infiltration, and nephrocalcinosis were also present. To the authors' knowledge, this present study is the first report of spontaneously occurring GCK in red piranhas and freshwater fish in general. Despite being rare, GCK is a condition with the potential to impair the health of fish and mammals, and further studies are needed to shed new light on this condition

Transient increase in chloride cell number and heat shock protein expression (hsp70) in brown trout (Salmo trutta fario) exposed to sudden temperature elevation

The native cold-adapted brown trout ( Salmo trutta fario ) is often the subject of biomonitoring field studies. Groups of trout were exposed to a sudden temperature rise, from 8 degrees C to 19 degrees C for two hours, and thereafter set back to 8 degrees C. Gill samples of control animals, of fish after the exposure period, and after 24 and 48 hours of recovery at a temperature of 8 degrees C were examined histologically, immunohistochemically, electron microscopically, and by Western blot analysis. By means of immunohistochemistry and electron microscopy, an increase of chloride cells was observed after the temperature elevation . During the recovery period the number of chloride cells decreased. Western blot analysis for stress proteins ( hsp70 ), widely used as a biomarker for environmental stress, was performed from skin and gill. Whereas in the gill both isoforms, the constitutive and the heat inducible form, of hsp70 were detected in all groups, in the skin the control animals only showed the constitutive form. After two hours of exposure both isoforms were visible. An increased expression of hsp70 could be demonstrated in both organs after the exposure. Comparison of the hsp70 values between gill and skin showed tissue-specific differences during the recovery period. In the gill hsp70 rapidly decreased, while in the skin the level remained elevated over the whole observation period. When hsp70 is used as a biomarker in field studies, the fast and organ-specific reaction in the gill and skin of brown trout has to be taken into consideration

Pollution control can help mitigate future climate change impact on European grayling in the UK

Aim: We compare the performance of habitat suitability models using climate data only or climate data together with water chemistry, land cover and predation pressure data to model the distribution of European grayling (Thymallus thymallus). From these models, we (a) investigate the relationship between habitat suitability and genetic diversity; (b) project the distribution of grayling under future climate change; and (c) model the effects of habitat mitigation on future distributions. Location: United Kingdom. Methods: Maxent species distribution modelling was implemented using a Simple model (only climate parameters) or a Full model (climate, water chemistry, land use and predation pressure parameters). Areas of high and low habitat suitability were designated. Associations between habitat suitability and genetic diversity for both neutral and adaptive markers were examined. Distribution under minimal and maximal future climate change scenarios was modelled for 2050, incorporating projections of future flow scenarios obtained from the Centre for Ecology and Hydrology. To examine potential mitigation effects within habitats, models were run with manipulation of orthophosphate, nitrite and copper concentrations. Results: We mapped suitable habitat for grayling in the present and the future. The Full model achieved substantially higher discriminative power than the Simple model. For low suitability habitat, higher levels of inbreeding were observed for adaptive, but not neutral, loci. Future projections predict a significant contraction of highly suitable areas. Under habitat mitigation, modelling suggests that recovery of suitable habitat of up to 10% is possible. Main conclusions: Extending the climate-only model improves estimates of habitat suitability. Significantly higher inbreeding coefficients were found at immune genes, but not neutral markers in low suitability habitat, indicating a possible impact of environmental stress on evolutionary potential. The potential for habitat mitigation to alleviate distributional changes under future climate change is demonstrated, and specific recommendations are made for habitat recovery on a regional basis

The impact of co-infections on fish: a review

International audienceAbstractCo-infections are very common in nature and occur when hosts are infected by two or more different pathogens either by simultaneous or secondary infections so that two or more infectious agents are active together in the same host. Co-infections have a fundamental effect and can alter the course and the severity of different fish diseases. However, co-infection effect has still received limited scrutiny in aquatic animals like fish and available data on this subject is still scarce. The susceptibility of fish to different pathogens could be changed during mixed infections causing the appearance of sudden fish outbreaks. In this review, we focus on the synergistic and antagonistic interactions occurring during co-infections by homologous or heterologous pathogens. We present a concise summary about the present knowledge regarding co-infections in fish. More research is needed to better understand the immune response of fish during mixed infections as these could have an important impact on the development of new strategies for disease control programs and vaccination in fish