STUDY OF A POSSIBLE TRANSMISSION OF VHS A ND IHN VIRUSES FROM INFECTED TROUT - FARMS TO WILD FISH POPULATIONS

The study took place on a portion of first category river of the Pas-d e-Calais, along which exist 4 trout farms infected by the virus VHS an d/or IHN. Electric fishing was carried out in June, September and Octo ber 1991 on 4 stretches up and downstream of the trout farms. This all owed a representative sampling of live fish other than salmonidae for virus isolation (85 analyses by batch of 3 or 5 individuals) and to re alize 96 serological tests for VHS and IHN on blood samples of trouts captured in the river. About sixty serological tests were also made in each of the 4 fish farms in December 1991. As far as the river is con cerned, all the virus isolations: and the serological tests were negat ive. Considering these results, the level of contamination and carriag e of rhabdoviruses in the natural milieu connected with infected trout farms seems relatively low, but this does not rule out the possibilit y of transmission by wild fish.