Low Likelihood of Intra-Ovum Infection with Flavobacterium psychrophilum in Cultured Salmonids in Japan

Abstract

We evaluated the occurrence of intra-ovum infection with Flavobacterium psychrophilum, the causative agent of bacterial cold-water disease (BCWD) and rainbow trout fry syndrome (RTFS), in the eggs of six salmonid species in Japan. Flavobacterium psychrophilum was isolated from four eggs in one of 13 lots of eyed eggs (999 eggs) imported from the United States. In contrast, the bacterium was not isolated from 28 lots (1,680 eggs) or 61 lots (3,693 eggs) of domestically produced unfertilized or eyed eggs, respectively. Our results indicate there is a low likelihood of intra-ovum infection in cultured salmonids in Japan.