Effects of fish size and route of infection on virulence of a Danish Yersinia ruckeri O1 biotype 2 strain in rainbow trout (Oncorhynchus mykiss)

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  • Maki Ohtani, Københavns Universitet
  • ,
  • Kasper Rømer Villumsen, Københavns Universitet
  • ,
  • Helene Kragelund Strøm, Københavns Universitet
  • ,
  • Anne Hjørngaard Lauritsen, BioMar A/S
  • ,
  • Bent Aalbæk, Københavns Universitet
  • ,
  • Inger Dalsgaard, National Veterinary Institute, Technical University of Denmark
  • ,
  • Barbara Nowak
  • Martin Kristian Raida, Københavns Universitet
  • ,
  • Anders Miki Bojesen

The comparative virulence of Yersinia ruckeri serotype O1 biotype 2 strain 07111224 from a Danish outbreak of enteric redmouth disease in rainbow trout (Oncorhynchus mykiss) was investigated in different sizes of rainbow trout (5, 19, 25 and 52 g) using a panel of challenge methods (bath, intraperitoneal (IP) injection, anal intubation and cohabitation). The results show that Y. ruckeri 07111224 is virulent enough to successfully cause mortality in 5–52 g rainbow trout through three different infection routes (bath, IP injection and anal intubation), and strongly suggests that susceptibility to Y. ruckeri infection is dependent on fish size. Bath challenge (10 8 CFU/ml) caused 79% mortality in 5 g fish, while the mortality in 19–52 g fish was approximately 26%. IP injection challenges (10 5 –10 6 CFU/individual) resulted in high mortalites in fish of all sizes. Anal intubation challenges (10 9 CFU/individual) induced 82% mortality in 5 g fish and decreased with increasing fish weight. Finally, cohabitation challenges induced 45% mortality in 5 g test fish when test fish were cohabitated 1:1 with shedder fish, while mortalities in test fish of five other challenge groups were lower (5–25%). Statistical models were fit to the data from each challenge model. The model parameter predictions suggests statistically significant effects of fish weight for bath, IP and anal intubation challenges. Furthermore, they highlight the importance of the ratio of shedders to test fish in cohabitation challenges and of the challenge doses, in particular for the IP challenge model.

OriginalsprogEngelsk
TidsskriftAquaculture
Vol/bind503
Sider (fra-til)519-526
Antal sider8
ISSN0044-8486
DOI
StatusUdgivet - mar. 2019

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