183 research outputs found
Mitigating human impacts including climate change on proliferative kidney disease in salmonids of running waters.
Over the last two decades, an increasing number of reports have identified a decline in salmonid populations, possibly linked to infection with the parasite Tetracapsuloides bryosalmonae and the corresponding disease, that is, proliferative kidney disease (PKD). The life cycle of this myxozoan parasite includes sessile bryozoan species as invertebrate host, which facilitates the distribution of the parasite in running waters. As the disease outcome is temperature dependent, the impact of the disease on salmonid populations is increasing with global warming due to climate change. The goal of this review is to provide a detailed overview of measures to mitigate the effects of PKD on salmonid populations. It first summarizes the parasite life cycle, temperature-driven disease dynamics and new immunological and molecular research into disease resistance and, based on this, discusses management possibilities. Sophisticated management actions focusing on local adaptation of salmonid populations, restoration of the riverine ecosystem and keeping water temperatures cool are necessary to reduce the negative effects of PKD. Such actions include temporary stocking with PKD-resistant salmonids, as this may assist in conserving current populations that fail to reproduce
Investigation of Proliferative Kidney Disease in Brown Trout and Habitat Characteristics Associated with a Swiss Wastewater Treatment Plant
Wastewater treatment plants (WWTP) play a critical role in mitigating adverse environmental
impacts of urban and industrial wastewater by removing pollutants and reducing the risk
of contamination. Discharges of treated effluents from WWTPs can still have significant effects on
freshwater ecosystems, particularly on sensitive species like brown trout. We analyzed the effects
of a modern WWTP on a freshwater ecosystem, studying fish biodiversity and biomass, the occurrence
of the parasitic disease Proliferative Kidney Disease (PKD) on brown trout, river water
temperatures throughout the year and fish habitat and diversity. No major differences between upand
downstream of the WWTP were observed in habitat structure and attractiveness, fish biomass
and species diversity, nor in PKD prevalence or intermediate host presence. However, immediately
at the WWTPâs effluent and continuing downstream, the water temperature rose by almost 1 °C.
While WWTPs are crucial for reducing the environmental impact of urban and industrial wastewater,
their effluents can still have important consequences for freshwater ecosystems. Brown trout are
particularly susceptible to increases in water temperature, especially regarding PKD severity and
consequent mortality. To ensure the long-term health and sustainability of freshwater ecosystems, it
is imperative to improve measures to minimize water temperature rises and mitigate downstream
cascade effects on sensitive organisms like brown trout
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
Application of UV-C irradiation prevented a severe outbreak of proliferative kidney disease in rainbow trout aquaculture
There is an urgent need to establish protocols on how to protect salmonids in aquaculture
from outbreaks of proliferative kidney disease (PKD). For this purpose, systems for a continuous
application of peracetic acid (PAA, 0.1 mg lâ1) and of ultraviolet C light (UV-C, 323.5â
158.6 mW s cmâ2) were installed in the inlet of raceway-channels within a sub-unit of a commercial
rainbow trout Oncorhynchus mykiss farm. After 127 d of rearing, a fish health examination
was conducted. Fish in the control and PAA treatment groups showed signs of PKD. In contrast,
fish in the UV-C treatment group showed almost no signs of disease based on clinical examinations
and necropsy. This observation indicates that UV-C irradiation could be a promising tool to
protect fish from PKD in the future
Geographic distribution of Tetracapsuloidesbryosalmonae infected fish in Swiss rivers: an update
Abstract.: Proliferative kidney disease (PKD) has been recognized as a potential threat to brown trout (Salmotrutta) populations in Switzerland. A study performed in 2000/2001 on 139 sampling sites from 127 rivers in Switzerland revealed a wide distribution of fish infected by Tetracapsuloidesbryosalmonae, the causative agent of PKD. The present study aimed to complement this dataset by studying a further 115 sample sites from 91 rivers and 4 fish farms. Mainly brown trout were investigated for the presence of T. bryosalmonae by a combination of macroscopical, histological and immunohistochemical examination. In approximately 56% of the examined sampling sites, T. bryosalmonae-infected fish were found. The prevalence of infected fish at individual sites ranged from 0% to 100%. Infection intensity, judged on the basis of histological and immunohistochemical evaluation for the degree of parasite infection, varied greatly between and within sites. PKD-positive sites were found in all areas of Switzerland. The wide distribution of the disease in Swiss rivers indicates that PKD may be a causative factor for the catch decline of brown trout, which was suggested over recent decades in Switzerlan
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
Histopathological alterations of the heart in fish: proposal for a standardized assessment.
Histopathological alterations in the heart are often reported in fish as a result of exposure to a variety of chemical compounds. However, researchers presently lack a standardized method for the evaluation of histopathological alterations in the cardiovascular system of fish and the calculation of an 'organ index'. Therefore, we designed a method for a standardized assessment and evaluation of histopathological alterations in the heart of fish. As a model species, we used rainbow trout Oncorhynchus mykiss, but the protocol was also successfully applied to other fish species belonging to different taxonomic orders. To test the protocol, we re-evaluated sections of atenolol-exposed and unexposed rainbow trout obtained in a previous study. The results were in accordance with those previously published, demonstrating the applicability of the protocol. The protocol provides a universal method for the comparative evaluation of histopathological changes in the heart of fish
First isolation of a rhabdovirus from perch Perca fluviatilis in Switzerland
Perca fluviatilis is a fish species of increasing interest to the Swiss fish farming industry. In recent years, recirculation systems have been specifically set up to increase production. In one of these farms, abnormal spiral swimming associated with elevated mortalities occurred in repeated batches of imported perch shortly after stocking on several occasions. No bacterial or
parasitic etiology was detected, but a virus grown in bluegill fry (BF-2) cells was identified as perch rhabdovirus. Subsequent investigations of other samples suggested a viral tropism for the central nervous system (CNS). Phylogenetic analysis of the partial N and entire G gene sequences positioned this isolate in genogroup C of the species Perch rhabdovirus, with high nucleotide and amino acid (aa) sequence identities with the DK5533 strain isolated in Denmark in 1989. Comparative studies using other closely related isolates allowed the distinction of 2 serological Patterns among perch rhabdoviruses and the identification of a proline substitution by a serine in Position 147 of the glycoprotein potentially involved in antigenic differentiation. Even if perch imported onto the farm tested negative by virus isolation prior to transport, they may have been the origin of this outbreak since CNS tissue was not included in the samples that were analyzed. Another possibility might be a sub-clinical infection with a viral load in resident fish too low to be detected.
This study reports the first isolation of a perch rhabdovirus in Switzerland, and emphasizes the necessity of optimizing diagnostic tools that facilitate better control of the risks associated with fish translocation
Assessment of fish health status in four Swiss rivers showing a decline of brown trout catches
Abstract.: A pronounced decline in catch of brown trout (Salmo trutta L.) over the last 10-20 years has been reported for many rivers in Switzerland. Impaired health status of the fishes has been suggested as one possible cause of the decline. The present study investigated the health status of juvenile brown trout from four Swiss rivers which experienced reductions of brown trout catches during the last two decades: Emme, Liechtensteiner Binnenkanal (LBK), Necker and Venoge. A gradient approach was applied, studying at each river a headwater (HW), midstream (D1) and downstream site (D2). Fish health was assessed by the following indices: hepatic 7-ethoxyresorufin-O-deethylase (EROD) activity, organ (liver, kidney) histopathology, and gross biometric indices (condition factor, hepatosomatic index). Hepatic EROD activities were generally low without showing significant within- or between-stream differences. Histopathological alterations of the liver displayed a moderate downstream increase in the Emme, LBK and Necker, but not in the Venoge. Between-stream differences of liver pathology were small. Kidney histopathology was not different between upstream and downstream sites, except for Emme and Venoge, where fishes at the downstream sites were infected with the parasite Tetracapsuloides bryosalmonae, the cause of the proliferative kidney disease (PKD). The findings from this study point to an association of within-stream gradients in water quality, PKD prevalence, fish health and brown trout biomass, whereas between-stream differences of actual fish health status reflecting the different levels of catch declines observed in the four rivers during the last two decades are not eviden
- âŠ