Susceptibility of Nile tilapia (Oreochromis niloticus) to vibriosis due to Vibrio vulnificus biotype 2 (serovar E)

The present study documents the susceptibility of Nile tilapia to the experimental vibriosis caused by Vibrio vulnificus biotype 2 (serovar E) using a reference strain (Spanish Collection of Type Cultures, CECT 4604) selected for its high degree of virulence for eels. The biotype 1 of this species is one of the usual organisms involved in epizootics occurred in tilapia. After intraperitoneal injection, the selected strain developed a haemorrhagic septicaemia similar to eel vibriosis with a LD50 four log units lower than that exhibited by the type strain of the species, which belongs to the biotype 1. The results obtained in waterborne and intubation challenges indicated that water and feed could act as a vehicle for vibriosis transmission to healthy tilapia. Moreover, live cells and the extracellular products derived from the strain CECT 4604 showed remarkable activity against tilapia erythrocytes, which correlated with the in vivo production of extensive haemorrhagic areas. Our results suggest that this bacterium could constitute a serious health hazard for tilapia, especially if it is cocultured with eels. Thus, vaccination of tilapia with a vaccine against V vulnificus biotype 2 could be the best strategy to prevent any cross transmission of the disease from eels to tilapia under intensive rearing conditions. (C) 2002 Published by Elsevier Science B.V.