POISONING OF CATTLE AND SHEEP IN URUGUAY BY SAWFLY (PERREYIA FLAVIPES) LARVAE

From June to early October of 1993, 1994 and 1995 at least 40 outbreak s of a highly lethal disease occurred in cattle and sheep in the centr al region of Uruguay. During 1995 total cattle losses probably exceede d 1000 head. Mortalities were 1.6%, 7.0% and 1.3% for calves, yearling s and adults, respectively, but mortalities up to 28% occurred on some farms. Sheep were less frequently affected than cattle. Most animals were just found dead. Cattle had weakness, muscular tremors, depressio n, stupor and death. Others became highly excited and aggressive. Most affected cattle died within 2 d. Jaundice and mild photosensitization were observed in cattle that survived longer. Cross and microscopic l esions were severe periacinar or massive necrosis of hepatocytes with prominent edema of the gall bladder wall and its attachments. Edema, e cchymoses and petechiae on serous membranes, ascites and dry content o f the omasum, colon and rectum were also observed. Invariably larval b ody fragments and heads of P flavipes were found in the rumen and omas um. The diagnosis of sawfly poisoning was confirmed by experimental fe eding of 3 sheep and 2 calves with 9 to 40 g of P flavipes larvae/kg b ody weight.