Heike Schmidt-Posthaus

Causes of mortality in reintroduced Eurasian lynx in Switzerland.

Seventy-two lynx, found dead in the Swiss Alps and the Jura Mountains (Switzerland) from 1987–99, were evaluated to determine the cause of death. Seventy-two per cent (52/72) of all animals died because of noninfectious diseases or causes such as vehicular collision and poaching. Eighteen percent (13/72) died from infectious diseases, including some which could have been transferred to the lynx from domestic animals or other wild animals such as panleukopenia and sarcoptic mange. If only radio-tagged animals (included in a monitoring program) were taken into consideration, the percentage of mortality caused by infectious diseases rose to 40%, indicating that infections might be underestimated in randomly found mortality events. We hypothesize that even a few cases of infections in a small population like the lynx, which are additionally threatened by noninfectious causes, may threaten the long term survival of the population.

Evaluation of Two Monitoring Approaches to Assess Effects of Waste Water Disposal on Histological Alterations in Fish

An active monitoring (caging experiment) and a passive monitoring (sampling of wild fish) were performed to investigate the effects of effluent from a sewage treatment works (STW) on brown trout (Salmo trutta) by histopathological examinations of the skin, gill, liver and kidney. Histopathological lesions were evaluated according to a standardised assessment tool, which allows calculation of indices for every organ. According to the results of both monitorings, trout exposed to river water supplemented with treated waste water from the STW Lyss showed higher histopathological indices than trout caught upstream of the discharge point of the STW or kept in river water only. These results indicate a negative effect of treated waste water from the STW on the histopathological status of the examined organs of brown trout. Both monitoring approaches revealed the liver to be the most affected organ compared with reference fish. However, data from the two monitoring approaches were not completely consistent: histologically the gills were the most sensitive organ to the effects of treated waste water in the active monitoring, but were not affected in the passive monitoring. The data provide relevant information about both the comparability and the pros and cons of the two monitoring approaches to assess effects of pollution on histopathological alterations in fish.

Proliferative kidney disease in rainbow trout: time- and temperature-related renal pathology and parasite distribution

Proliferative kidney disease is a parasitic infection of salmonid fishes caused by Tetracapsuloides bryosalmonae. The main target organ of the parasite in the fish is the kidney. To investigate the influence of water temperature on the disease in fish, rainbow trout Oncorhynchus mykiss infected with T bryosalmonae were kept at 12 degrees C and 18 degrees C. The number of parasites, the type and degree of lesions in the kidney and the mortality rate was evaluated from infection until full development of disease. While mortality stayed low at 12 degrees C, it reached 77% at 18 degrees C. At 12 degrees C, pathological lesions were dominated by a multifocal proliferative and granulomatous interstitial nephritis. This was accompanied by low numbers of T. bryosalmonae, mainly located in the interstitial lesions. With progression of the disease, small numbers of parasites appeared in the excretory tubuli, and parasite DNA was detected in the urine. Parasite degeneration in the interstitium was observed at late stages of the disease. At 18 degrees C, pathological lesions in kidneys were more severe and more widely distributed, and accompanied by significantly higher parasite numbers. Distribution of parasites in the renal compartments, onset of parasite degeneration and time course of appearance of parasite DNA in urine were not clearly different from the 12 degrees C group. These findings indicate that higher mortality at 18 degrees C compared to 12 degrees C is associated with an enhanced severity of renal pathology and increased parasite numbers.

Presence of UV filters in surface water and the effects of phenylbenzimidazole sulfonic acid on rainbow trout (Oncorhynchus mykiss) following a chronic toxicity test

UV filters belong to a group of compounds that are used by humans and are present in municipal waste-waters, effluents from sewage treatment plants and surface waters. Current information regarding UV filters and their effects on fish is limited. In this study, the occurrence of three commonly used UV filters - 2-phenylbenzimidazole-5-sulfonic acid (PBSA), 2-hydroxy-4-methoxybenzophenone (benzophenone-3, BP-3) and 5-benzoyl-4-hydroxy-2-methoxy-benzenesulfonic acid (benzophenone-4, BP-4) - in South Bohemia (Czech Republic) surface waters is presented. PBSA concentrations (up to 13μgL(-1)) were significantly greater than BP-3 or BP-4 concentrations (up to 620 and 390ngL(-1), respectively). On the basis of these results, PBSA was selected for use in a toxicity test utilizing the common model organism rainbow trout (Oncorhynchus mykiss). Fish were exposed to three concentrations of PBSA (1, 10 and 1000µgL(-1)) for 21 and 42 days. The PBSA concentrations in the fish plasma, liver and kidneys were elevated after 21 and 42 days of exposure. PBSA increased activity of certain P450 cytochromes. Exposure to PBSA also changed various biochemical parameters and enzyme activities in the fish plasma. However, no pathological changes were obvious in the liver or gonads.

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 degrees C after an initial exposure to an infectious environment at 12-16 degrees 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 degrees C and all other groups. Differences in parasite load between fish kept at 14 degrees C to 19 degrees C were not significant. These findings provide evidence that there is no direct link between parasite intensity and fish mortality.

The teleostean liver as an immunological organ: Intrahepatic immune cells (IHICs) in healthy and benzo[a]pyrene challenged rainbow trout (Oncorhynchus mykiss)

The existence of a resident population of intrahepatic immune cells (IHICs) is well documented for mammalian vertebrates, however, it is uncertain whether IHICs are present in the liver of teleostean fish. In the present study we investigated whether trout liver contains an IHIC population, and if so, what the relative cellular composition of this population is. The results provide clear evidence for the existence of an IHIC population in trout liver, which constitutes 15-29% of the non-hepatocytes in the liver, and with a cellular composition different to that of the blood leukocyte population. We also analyzed the response of IHICs to a non-infectious liver challenge with the hepatotoxic and immunotoxic chemical, benzo[a]pyrene (BaP). Juvenile trout were treated with BaP (25 or 100mg/kgbw) at levels sufficient to induce the molecular pathway of BaP metabolism while not causing pathological and inflammatory liver changes. The IHIC population responded to the BaP treatments in a way that differed from the responses of the leukocyte populations in trout blood and spleen, suggesting that IHICs are an independently regulated immune cell population.

Effects of wastewater on fish health: an integrated approach to biomarker responses in brown trout (Salmo trutta L.)

The impact of wastewater effluent from a sewage treatment works (STW) on the health of brown trout held in cages and wild brown trout in a river was investigated. Biochemical, histological, and organismal responses as well as parasite abundances were monitored and then analyzed using multivariate analyses. Stress responses in trout induced by the water quality of the river upstream of the STW were enhanced by the discharge of the STW. For caged fish, the serum chemistry values alkaline phosphatase, blood urea nitrogen, and creatinine, as well as histological indices of gills and liver, were most effective at distinguishing among fish held in river water, a mixture of river water and wastewater, and tap water. For wild fish, total protein, histological liver alterations and abundance of two parasites (sessile peritrichia, Sphaerospora sp.) were the most indicative parameters for discriminating the health of fish between sites upstream and downstream of the STW. Considering the relationships between the measured parameters concurrently, the multivariate discriminant analysis is an effective method to evaluate which combination of parameters provide the best discrimination between the treatment groups. In contrast to the calculation of group differences based on individual responses, the integrated responses of parameters representing different biological levels lead to a more comprehensive assessment of organismal health and a more accurate distinction in differences between treatment groups.

Severe Scuticociliate (Philasterides dicentrarchi) Infection in a Population of Sea Dragons (Phycodurus eques and Phyllopteryx taeniolatus)

Scuticociliatosis is a disease of fish induced by ciliated parasites of the genus Scuticociliatida. It has been described in sea horses (Hippocampus sp.), flounders (Paralichthys olivaceus), and turbots (Scophthalmus maximus). Here we present a case study of a population of sea dragons chronically infected with scuticociliates identified as Philasterides dicentrarchi by histopathology and PCR. Beginning in 2004, over a period of 19 months, 10 sea dragons (Phycodurus eques and Phyllopteryx taeniolatus) were found dead in an aquarium of the Zoological Garden Basle, Switzerland. Clinically, the animals showed only faint symptoms of disease over a short period of time. At necropsy, macroscopic lesions were confined to the skin with multiple, often hemorrhagic, ulcerations. Histologically, epidermal ulcers were associated with necrosis and inflammation of the underlying dermis and musculature. Numerous ciliates, with a morphology consistent with scuticociliates, were present in these lesions. In several animals these ciliates had invaded blood vessels and were detected in gills and internal organs including kidney, thyroid gland, and central nervous system (CNS). In these organs, mild degenerative lesions and inflammatory reactions were evident. The ciliates were identified as Philasterides dicentrarchi based on small-subunit ribosomal RNA (SSUrRNA) gene sequences obtained by polymerase chain reaction (PCR) on DNA extracted from paraffin-embedded tissue sections. Our report shows that scuticociliate infections of sea dragons can develop into a systemic infection and that both species of sea dragons can be affected.

Candidatus Syngnamydia Venezia, a Novel Member of the Phylum Chlamydiae from the Broad Nosed Pipefish, Syngnathus typhle

Chlamydia are obligate intracellular bacteria and important pathogens of humans and animals. Chlamydia-related bacteria are also major fish pathogens, infecting epithelial cells of the gills and skin to cause the disease epitheliocystis. Given the wide distribution, ancient origins and spectacular diversity of bony fishes, this group offers a rich resource for the identification and isolation of novel Chlamydia. The broad-nosed pipefish (Syngnathus typhle) is a widely distributed and genetically diverse temperate fish species, susceptible to epitheliocystis across much of its range. We describe here a new bacterial species, Candidatus Syngnamydia venezia; epitheliocystis agent of S. typhle and close relative to other chlamydial pathogens which are known to infect diverse hosts ranging from invertebrates to humans.

Novel Chlamydiales associated with epitheliocystis in a leopard shark Triakis semifasciata

The Chlamydiales is a diverse order of obligate intracellular gram-negative bacteria that are known to cause a wide range of diseases in terrestrial animals, including humans. Molecular analyses have revealed that these organisms are also associated with epitheliocystis in teleost fish species, highlighting the suspected deep evolutionary origin of members of this bacterial order. However, our knowledge of their fish host range and of the diversity of the bacteria themselves is still very limited. In this study, we provide molecular evidence for a novel member of the Order Chlamydiales in a nonteleost species, the leopard shark Triakis semifasciata. Based on phylogenetic analysis of the 16S rRNA gene, this novel organism appears to represent a unique lineage in the Order Chlamydiales despite appearing histologically similar to epitheliocystis-causing organisms in other fish species. A greater understanding of the genetic diversity of marine Chlamydiales will assist our attempts to manage and control epitheliocystis outbreaks and to understand the evolution of this unique obligate intracellular pathogen.