PRELIMINARY STUDIES EXAMINING THE INFECTION OF RAINBOW TROUT EGGS WITH FLAVOBACTERIUM PSYCHROPHILUM USING CONFOCAL MICROSCOPY

摘要

Flavobacterium psychrophilum (Fp), the causative agent of rainbow trout fry syndrome (RTFS) and cold water disease (CWD), is one of the most important bacterial pathogens in freshwater salmonid aquaculture in Europe, as well as in USA, Chile and Japan. Fp has been isolated from brood fish, suggesting that vertical transfer of Fp from the brood fish to offspring may constitute a potential route of infection (Brown et al., 1997). Vertical transfer of Fp has not been fully substantiated, although numerous studies have been carried out to do so. Thus, there is a need to verify suggestions that Fp can be introduced and survive within rainbow trout eggs. A plausible explanation for the transfer of Fp from brood fish to fry is the introduction of bacteriainto the eggs during the fertilisation process. In the present study, rainbow trout eggs were infected with Fp under laboratory conditions during either the fertilisation or the egg-hardening process. The infected eggs were then examined for the presenceof Fp by confocal microscopy, nested PCR, bacterial culture and scanning electron microscopy.