First report of a yersiniosis-like infection in Iranian farmed rainbow trout

A chronic infection resembling yersiniosis with a total mortality of 10-20% occurred in some farmed rainbow trout in Charmohal and Bakhtiari province, Iran during summer 1997. Generally, the affected fish were anorexic, letha rgic and showed darkening of body, lesions on the head and dorsal sites, ex ophthalmia. reddening of mouth, opercula and fins. Bacteriological culture from skin lesions, kidney, liver, spleen and lower parr of intestine obtain ed from 200 affected or apparently healthy fish (6-9.5 and 10-18 cm in leng th) resulted in no significant pathogenic bacteria of fish except some stra ins of Yersinia sp, Edwardsiella sp., and Flexibacter/Cytophaga-like bacter ia, Morphological. physiological and biochemical characteristics as well ii s serological tests, slide agglutination and indirect immunefluorescence an tibody rest. confirmed detection of Yersinia ruckeri-like organisms in affe cted Fish. This is the first finding of Yersinia infection in Iranian cold- water aquaculture industry.