Papers by H. Schmidt-posthaus
First report of puffy skin disease in farmed rainbow trout Oncorhynchus mykiss from Switzerland
Bulletin of the European Association of Fish Pathologists
Puffy skin disease (PSD) is an economically important syndrome in rainbow trout, Oncorhynchus myk... more Puffy skin disease (PSD) is an economically important syndrome in rainbow trout, Oncorhynchus mykiss (Walbaum, 1792). Because of its horizontal transmission, an infectious aetiology was hypothesised. However, aetiology remains unknown so far. PSD was first reported in 2002 in fish farms in England. Since then, cases have increased significantly, with additional reports in still water fisheries. Typically, the prevalence and severity of PSD increase during the summer and autumn months (13°C – 15°C). In February 2022, rainbow trout from a mountainous fish farm in Switzerland showed lethargy, inappetence, white to grey patches on the skin and slightly increased mortality. Twenty-one rainbow trout were submitted for diagnostics to the Institute for Fish and Wildlife Health, University of Bern, Switzerland. On post-mortem examination, 7/21 had up to 75% to 90% of the skin surface affected with bilateral, focally extensive white to grey, rough patches. The scales on the affected areas wer...
Scuticociliate (Philasterides dicentrarchi) infection cluster in a multispecies marine aquarium system
Diseases of Aquatic Organisms
Scuticociliatosis, caused by ciliated protozoa of the subclass Scuticociliatia, has been associat... more Scuticociliatosis, caused by ciliated protozoa of the subclass Scuticociliatia, has been associated with high mortalities in marine fish. Environmental factors such as an increase in water temperature can enhance this disease. The aim of the present report is to describe the occurrence of a cluster of cases of scuticociliatosis in a multispecies marine cold-water system in a public aquarium. Philasterides dicentrarchi was identified by PCR in formalin-fixed tissues of some of the fish showing meningitis or meningoencephalitis, dermatitis and myositis with intralesional protozoa. An increase in water temperature of approximately 2°C was identified as a potential contributing factor for this cluster of infections. Higher temperature may have enhanced the propagation or pathogenicity of scuticociliates or increased host susceptibility of some species of fish, especially wolf-eel Anarrhichthys ocellatus and spotted ratfish Hydrolagus colliei. This report also highlights the complexity o...
Lethal Infection of Atlantic Puffins (Fratercula arctica) with Diplostomum Baeri, Transmitted by Feeding Infected European Minnows (Phoxinus phoxinus)
Journal of Comparative Pathology, 2022
Journal of Wildlife Diseases, 2002
Seventy-two lynx, found dead in the Swiss Alps and the Jura Mountains (Switzerland) from 1987-99,... more 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.
Veterinary pathology, 2008
Scuticociliatosis is a disease of fish induced by ciliated parasites of the genus Scuticociliatid... more 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 les...
Journal of Fish Biology, 1999
Brown trout Salmo trutta populations of numerous Swiss rivers are declining. Sewage plant effluen... more Brown trout Salmo trutta populations of numerous Swiss rivers are declining. Sewage plant effluents are discussed as a possible cause. To investigate the influence of sewage plant effluents, brown trout as well as rainbow trout Oncorhynchus mykiss were exposed to 10% diluted waste water over a period of 12 months. The effects were compared to those on trout kept in commercial tap water. The mortality rate was low and no pathogenic bacteria or viruses were recorded in exposed and tap-water animals. Parasitological examination revealed a mild infestation with Gryodactylus sp. in all groups. Macroscopically and histologically, only minor changes in gills, skin, and kidney of exposed animals were found when compared to fish kept in tap water. Degenerative and inflammatory reactions in the liver of exposed animals were the most prominent findings. Several brown trout caught in the River Langete showed marked proliferative, degenerative and inflammatory lesions of gills, liver, and kidney. The results do not suggest that waste-water effects would explain the decrease of fish populations. However, it is conceivable that the effluents in combination with other factors in the river enhance the development of changes.
Role of altitude and water temperature as regulating factors for the geographical distribution of Tetracapsuloides bryosalmonae infected fishes in Switzerland
Journal of Fish Biology, 2008
The role of water temperature and altitude of the river sites on distribution, prevalence and inf... more The role of water temperature and altitude of the river sites on distribution, prevalence and infection intensity of Tetracapsuloides bryosalmonae infected salmonids was investigated. The study is based on a 6 year survey of salmonids, mainly brown trout, Salmo trutta from 2000 to 2006 at 287 sampling sites across Switzerland. Almost 7000 fishes were tested for the presence of T. bryosalmonae by histological and immunohistochemical techniques. A good correlation between altitude and water temperature in Swiss rivers could be demonstrated. Therefore, the relation between altitude and sites tested for T. bryosalmonae infected fishes was investigated since water temperature values from these sites were not available. Percentage of sites with positive (infected) fishes was identical for altitudes between 200 and 800 m above sea level (m a.s.l.), while above 800 m a.s.l. only three sites with infected fishes were recorded. Site-specific prevalence values ranging from 0 to 100% and infection intensities from 0 to 6 were found over the whole altitude range from 200 to 800 m a.s.l., and no correlation with altitude was found. Conditions at altitudes >800 m may not be favourable for the establishment of the infection in fishes. With rising temperatures due to climatic changes, however, the prevalence of T. bryosalmonae infected fishes in altitudes >800 m a.s.l. could increase.
Sudden outbreak of metastatic intestinal adenocarcinoma in rainbow trout Oncorhynchus mykiss
Diseases of Aquatic Organisms
Intestinal adenocarcinomas are uncommon in fishes. To date, they have been reported in zebrafish ... more Intestinal adenocarcinomas are uncommon in fishes. To date, they have been reported in zebrafish Danio rerio, blue gularis Fundulopanchax sjostedti, koi carp Cyprinus carpio koi, Atlantic salmon Salmo salar and rainbow trout Oncorhynchus mykiss. Metastases are even rarer and have been observed so far at very low prevalence, only in feed-induced adenocarcinoma in Atlantic salmon and rainbow trout. Intestinal adenocarcinoma with liver and heart metastases and mesenteric invasion was found in approximately 33% of 4 yr old rainbow trout from a Slovene hatchery with 2000 breeding trout. During stripping, lumps in the abdominal cavity were palpated in one-third of the breeding fish; some of the fish were anorectic and lethargic, and mortality was slightly increased. Affected trout were euthanized and 4 were submitted for necropsy and histopathology. Necropsy revealed firm, whitish, irregularly lobular masses originating from the intestine. Histologically, the intestinal masses showed a pr...
Preliminary investigation of an idiopathic muscle disease in farmed burbot Lota lota
Diseases of Aquatic Organisms
The rearing of less established fish species in recirculating aquaculture systems (RASs) is incre... more The rearing of less established fish species in recirculating aquaculture systems (RASs) is increasing, but may require adaptations of the rearing facilities if health impairments occur. We observed several health issues in burbot Lota lota reared for up to 2 yr in a RAS and used microbiological, histological and molecular-biological methods to identify the causative agents. Minor skin trauma led to the development of ulcers. In addition, several fillets of burbot showed pronounced granulomatous inflammation and calcification with signs of muscle fiber degeneration which resembled a condition called ‘sandy flesh disease’ in North American walleye. Several infectious agents were able to be excluded as a cause for the disease. Carnobacterium maltaromaticum was isolated in high numbers in some of the affected muscle tissue. However, the role of this bacterium or other causative agents or husbandry conditions remains to be elucidated.
Mysterious Syndrome Causing High Mortality in Wild Brown Trout in Eastern Switzerland, Similar to Proliferative Darkening Syndrome – Pathology and Possible Causes
Journal of Comparative Pathology
Piscine mycobacteriosis – Involvement of bacterial species and reflection in pathology
Schweiz Arch Tierheilkd
Identification of important pathogens in European perch (Perca fluviatilis) culture in recirculating aquaculture systems
Aquaculture International
Characteristics of bacterial isolates in Swiss farmed and ornamental fish from a retrospective study from 2000 to 2017
Schweiz Arch Tierheilkd
Journal of Fish Diseases
pitheliocystis in Swiss brown trout (Salmo trutta) is a chlamydial infection, mainly caused by Ca... more pitheliocystis in Swiss brown trout (Salmo trutta) is a chlamydial infection, mainly caused by Candidatus Piscichlamydia salmonis and Candidatus Clavichlamydia salmonicola. To gain a better understanding of the temporal development of infections in wild brown trout, we investigated epitheliocystis infections during the course of the summer and autumn months of a single year (2015), and compared this to sampling points over the span of the years 2012-2014. The survey focused on tributaries (Venoge and Boiron) of the Rhone flowing in to Lake Geneva. When evaluated histologically, epitheliocystis infections were found throughout the period of investigation with the exception of the month of June. Fifty to 86 animals per sampling were investigated. Highest prevalence and infection intensities were seen in September. A correlation between epitheliocystis infection and water temperatures was not evident. Interyear comparison revealed consistent levels of prevalence and infection intensities in late summer. The absence of infections in June, combined with the consistent interyear results, indicates seasonal fluctuation of epitheliocystis infections in brown trout with a reservoir persisting during winter months from which infections can re-initiate each year. This could either be at levels below detection limits within the brown trout population itself or in an alternative host.
Are brown trout Salmo trutta fario and rainbow trout Oncorhynchus mykiss two of a kind? A comparative study of salmonids to temperature-influenced Tetracapsuloides bryosalmonae infection
Journal of Fish Diseases
Diseases of aquatic organisms, Jan 21, 2017
Proliferative kidney disease (PKD) is an emerging disease threatening wild salmonid populations, ... more Proliferative kidney disease (PKD) is an emerging disease threatening wild salmonid populations, with the myxozoan parasite Tetracapsuloides bryosalmonae as the causative agent. Species differences in parasite susceptibility and disease-induced mortality seem to exist. The aim of the present study was to compare incidence, pathology and mortality of PKD in grayling Thymallus thymallus and brown trout Salmo trutta under identical semi-natural conditions. Young-of-the-year grayling and brown trout, free of T. bryosalmonae, were jointly exposed in cage compartments in a river in the northeast of Switzerland during 3 summer months. Wild brown trout were caught by electrofishing near the cage, and PKD status was compared with that of caged animals. Cage-exposed grayling showed a PKD incidence of 1%, regardless of whether parasite infection was determined by means of real-time PCR or histopathology/immunohistochemistry. In contrast, PKD incidence of caged brown trout was 77%. This value w...
Frequency and histologic characterization of celomatic neoplasms in Koi (Cyprinus carpio koi)
Diseases of Aquatic Organisms, 2016
Chlamydia are obligate intracellular bacteria and important pathogens of humans and animals. Chla... more 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.
Non-infectious disorders of coldwater fish
Diseases and disorders of finfish in cage culture, 2003
... can be generated for both increased and decreased aggression resulting from domestication (Ru... more ... can be generated for both increased and decreased aggression resulting from domestication (Ruzzante, 1994). ... similar to the multiple pre-sentations of fat oxidation in other domestic species, there ... Algal Blooms Toxic algal blooms are a cause of cata-strophic losses to marine ...
Histopathological alterations of the heart in fish: proposal for a standardized assessment index
Diseases of Aquatic Organisms, 2016
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Papers by H. Schmidt-posthaus