sentence: The prevailing consensus is that the pathway of transmission of red mouth disease in fish is gastrointestinal yet the similarities of Y. ruckeri genome reduction to Y. pestis hint at an alternative mode of infection for Y. ruckeri.This comparative genomic study reaffirms that the distinguishing features of the high-level mammalian pathogens is the acquisition of a particular set of mobile elements : HPI , the pYV , pMT1 and pPCP plasmids , and the YADI island .