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Title: Multiple independent emergence of biotype 2 Yersinia ruckeri in the United States and Europe

item Welch, Timothy - Tim
item VERNER-JEFFREYS, DAVID - Centre For Environment, Fisheries And Aquaculture Science (CEFAS)

Submitted to: International Aquatic Animal Health Symposium Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 9/2/2010
Publication Date: 9/6/2010
Citation: Welch, T.J., Verner-Jeffreys, D. 2010. Multiple independent emergence of biotype 2 Yersinia ruckeri in the United States and Europe. International Aquatic Animal Health Symposium Proceedings. 6:107.

Interpretive Summary:

Technical Abstract: Biotype 2 (BT2) variants of the bacterium Yersinia ruckeri are an emerging disease problem in US and European salmonid aquaculture. The emergence of this biotype has been associated with an increased frequency of enteric redmouth disease (ERM) outbreaks in previously vaccinated salmonid fish. We used a genetic complementation approach to identify the specific natural mutations that cause the concomitant loss of motility and secreted lipase activity (BT2 phenotype) in BT2 strains of Y. ruckeri from the US, the UK and mainland Europe. Four independent lineages of BT2 Y. ruckeri were identified each containing a unique mutation in a gene encoding an essential component of the flagellar secretion apparatus. Our results demonstrate the existence of independent mutations leading to the BT2 phenotype thus demonstrating that this phenotype has emerged separately at least four times. In addition, BT2 strains from the UK were shown to have the same mutant allele found in US BT2 strains suggesting a common origin of this BT2 lineage. This differentiation of distinct BT2 lineages is of critical importance for the development and validation of vaccination or other treatment strategies intended for the control of BT2 strains.