A water temperature regime which prevents the occurrence of proliferative kidney disease (PKD) in rainbow trout, Oncorhynchus mykiss (Walbaum)

• Published in: Journal of fish diseases Vol. 24; no. 8; pp. 489 - 493
• Main Authors: De Kinkelin, P, Loriot, B
• Format: Journal Article
• Language: English
• Published: Oxford UK Blackwell Science Ltd 01.10.2001
• Subjects: Freshwater; Oncorhynchus mykiss; Tetracapsula bryosalmonae
• ISSN: 0140-7775; 1365-2761
• DOI: 10.1046/j.1365-2761.2001.00312.x

Proliferative kidney disease (PKD) is a hyperplastic condition of the principal lymphoid tissue of salmonid fish infected with Tetracapsula bryosalmonae, a myxozoan parasite. Initial observations of the disease at a fish farming site, demonstrated that its occurrence is associated with seasonal increases in water temperature, with the surviving fish becoming resistant to further overt PKD infection. Investigations into the induction of naturally-acquired PKD resistance have analysed the course of infection in fish infected at non-permissive water temperatures and later transferred to a permissive temperature. Rainbow trout, Oncorhynchus mykiss, were held for 4 weeks in a known T. bryosalmonae-infected site, during autumn and winter at water temperatures below 12-13 degree C. The status of parasitic infection was assessed by transfer of the fish to laboratory facilities supplied with water at 16 degree C. Temperature management led to protection against PKD when rainbow trout were exposed to the parasite for 4 weeks in May, at an average water temperature of 14-15 degree C, and then kept for 1 year in laboratory facilities at 12 degree C. They developed a very mild nephromegaly, did not undergo mortality, and did not develop PKD when re-exposed to enzootic water at a permissive temperature the next spring. Although effective against PKD, such a temperature regime is hardly achievable under trout farming conditions. We report here that rainbow trout which have accumulated 1300 day x degrees at water temperatures averaging 10-11 degree C in waters enzootic for PKD, acquire resistance to the parasite and do not develop clinical signs of PKD.