Abstract
Desquamative enteritis, due to a Vibrio and externally displays white gut, occurred among larval Japanese flounder (Paralichthys olivaceus) reared at the Hiroshima Prefectural Fisheries Experimental Station in 1986 and the Mie Prefectural Fisheries Experimental Station in 1988. Vibrio sp. INFL group that has been confirmed to be a causative bacterium of this disease by experimental infection (MASUMURA et al., 1989) was the dominant isolate from diseased fish. In this study an indirect immunofluorescent technique and a histopathological study were performed to reveal the invasiveness of Vibrio sp. INFL group into intestinal tissues. Slight infectious lesions occurred in the mucosae of posterior part of intestine and the rectum. These lesions showed separation of affected mucosal cells with invasions of numbers of Vibrio sp. INFL group that were revealed by the specific fluorescence. Extended intestinal lesions involved the posterior half of intestine and the rectum. They showed marked bacterial multiplication in mucosae and the underlying tunica propria, and extensively slouphed mucosae, indicating that the histological characteristic was desquamative enteritis. The invasive bacteria were revealed to be Vibrio sp. INFL group by the specific fluorescence. Other visceral organs were spared of the bacterial invasions. The damage of intestine and rectum would induce fish mortalities.
