Preliminary description of lesions in juvenile largemouth bass injected with largemouth bass virus

Juvenile largemouth bass Micropterus salmoides were intraperitoneally injec ted with largemouth bass Virus (LMBV), a member of the genus Ranavirus, fam ily Iridoviridae. Moribund fish which had been injected with 10(6.2) tissue culture infectious doses, 50% endpoint (TCID50), were sampled 4 d after in jection; other largemouth bass injected with this dose died between 3 and 5 d after injection. Fish injected with 10(2,8) TCID50 of LMBV were also exa mined after 4 d and had lesions similar to those of fish injected with the high dose. Clinical signs included darker pigmentation, inflammation and ne crosis at the site of injection, distended abdomen, corkscrew swimming, and lateral recumbency. Internally, fish had focally pale livers, bright red s pleens and reddened intestinal ceca. Histologically acute fibrinous periton itis affected the surface of all organs in the peritoneal cavity, but deepe r portions of organs appeared normal. There was also necrosis of the gastro intestinal mucosa. Except for the injection site, lesions were confined to the peritoneal cavity.