DAO 119:117-128 (2016)  -  DOI: https://doi.org/10.3354/dao02993

First Proliferative Kidney Disease outbreak in Austria, linking to the aetiology of Black Trout Syndrome threatening autochthonous trout populations

Bartolomeo Gorgoglione1,*, Mohamed H. Kotob1,2, Günter Unfer3, Mansour El-Matbouli

1Clinical Division of Fish Medicine, Department for Farm Animals and Veterinary Public Health, University of Veterinary Medicine, Veterinärplatz 1, 1210 Vienna, Austria
2Department of Pathology, Faculty of Veterinary Medicine, Assiut University, 71526, Assiut, Egypt
3Institute of Hydrobiology and Aquatic Ecosystem Management, Department for Water-Atmosphere-Environment, University of Natural Resources and Life Sciences, Max-Emanuel Straße 17, 1180 Vienna, Austria
*Corresponding author:

ABSTRACT: Proliferative Kidney Disease (PKD) was diagnosed in juvenile autochthonous brown trout Salmo trutta for the first time in Austria during summer 2014. Cytology showed Tetracapsuloides bryosalmonae sporoblasts, and histology revealed sporogonic (coelozoic) and extrasporogonic (histozoic) stages. Analysis of malacosporean ribosomal small subunit revealed that this strain is closely related to European isolates, although its source is unknown. Infection and high pathogenicity were reproduced upon a pre-restocking test with specific pathogen free (SPF) juvenile trout, resulting in 100% mortality between 28 and 46 d post exposure (dpe), with high ectoparasitosis. Fish showed grade 2 of the Kidney Swelling Index and grade 3 of the PKD histological assessment. T. bryosalmonae enzootic waters were demonstrated in further locations along the River Kamp, with infected bryozoans retrieved up to 6 km upstream of the farm with the PKD outbreak. Fredericella sultana colonies collected from these locations were cultivated in laboratory conditions. Released malacospores successfully induced PKD, and contextually Black Trout Syndrome (BTS), in SPF brown trout. In the absence of co-infections mortality occurred between 59 and 98 dpe, with kidneys enlarged up to 6.74% of total body weight (normal 1.23%). This study confirms the first isolation of a pathogenic myxozoan from an Austrian river tributary of the Danube, where its 2-host life cycle is fully occurring. Its immunosuppressant action could link PKD as a key factor in the multifactorial aetiology of BTS. This T. bryosalmonae isolation provides an impetus to undertake further multi-disciplinary research, aiming to assess the impact of PKD and BTS spreading to central European regions.


KEY WORDS: Tetracapsuloides bryosalmonae · Myxozoans · PKD · BTS · Salmo trutta · Oncorhynchus mykiss · Fredericella sultana · Bryozoans · Co-infection · Fish disease


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Cite this article as: Gorgoglione B, Kotob MH, Unfer G, El-Matbouli M (2016) First Proliferative Kidney Disease outbreak in Austria, linking to the aetiology of Black Trout Syndrome threatening autochthonous trout populations. Dis Aquat Org 119:117-128. https://doi.org/10.3354/dao02993

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