Inter-Research > DAO > v104 > n1 > p23-34  
Diseases of Aquatic Organisms

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DAO 104:23-34 (2013)  -  DOI:

Complex interaction between proliferative kidney disease, water temperature and concurrent nematode infection in brown trout

Heike Schmidt-Posthaus1,*, Pascale Steiner2,3, Barbara Müller1, Ayako Casanova-Nakayama1

1Centre for Fish and Wildlife Health, Institute of Animal Pathology, University of Berne, Laenggassstrasse 122, PO Box 8466, 3001 Berne, Switzerland
2Federal Office for the Environment FOEN, 3003 Bern, Switzerland
3Present address: Ecowert GmbH, Denter Tumas 6, 7013 Domat/Ems, Switzerland

ABSTRACT: Proliferative kidney disease (PKD) is a temperature-dependent disease caused by the myxozoan Tetracapsuloides bryosalmonae. It is an emerging threat to wild brown trout Salmo trutta fario populations in Switzerland. Here we examined (1) how PKD prevalence and pathology in young-of-the-year (YOY) brown trout relate to water temperature, (2) whether wild brown trout can completely recover from T. bryosalmonae-induced renal lesions and eliminate T. bryosalmonae over the winter months, and (3) whether this rate and/or extent of the recovery is influenced by concurrent infection. A longitudinal field study on a wild brown trout cohort was conducted over 16 mo. YOY and age 1+ fish were sampled from 7 different field sites with various temperature regimes, and monitored for infection with T. bryosalmonae and the nematode Raphidascaris acus. T. bryosamonae was detectable in brown trout YOY from all sampling sites, with similar renal pathology, independent of water temperature. During winter months, recovery was mainly influenced by the presence or absence of concurrent infection with R. acus larvae. While brown trout without R. acus regenerated completely, concurrently infected brown trout showed incomplete recovery, with chronic renal lesions and incomplete translocation of T. bryosalmonae from the renal interstitium into the tubular lumen. Water temperature seemed to influence complete excretion of T. bryosalmonae, with spores remaining in trout from summer-warm rivers, but absent in trout from summer-cool rivers. In the following summer months, we found PKD infections in 1+ brown trout from all investigated river sites. The pathological lesions indicated a re-infection rather than a proliferation of remaining T. bryosalmonae. However, disease prevalence in 1+ trout was lower than in YOY.

KEY WORDS: Tetracapsuloides bryosalmonae · PKD · Raphidascaris acus · Water temperature · Salmo trutta fario · Pathology · Recovery

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Cite this article as: Schmidt-Posthaus H, Steiner P, Müller B, Casanova-Nakayama A (2013) Complex interaction between proliferative kidney disease, water temperature and concurrent nematode infection in brown trout. Dis Aquat Org 104:23-34.

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