28th ANNUAL EASTERN FISH HEALTH WORKSHOP April 21-25, 2003 Visceral Toxicosis Of Catfish: An Emerging Disease Lester Khoo1 and William Holmes2 1University of Pennsylvania, School of Veterinary Medicine, New Bolton Center, 382 West Street Road, Kennett Square, PA 19348; 2Mississippi State Chemical Laboratory, Mississippi State University, P.O. Box CR, Mississippi State, MS 39762 In the spring of 1998, several channel catfish (Ictalurus punctatus) producers in the Mississippi Delta reported that they had experienced extremely heavy losses in ponds, which contained brood or harvest-size fish.  Often these farmers reported that abnormal behavior such as porpoising and swimming in large schools preceded devastating losses and the affected fish were found limp along the banks of the ponds. Most fish did not have gross external lesions, but an occasional fish had portions of its gastrointestinal tract protruding from the mouth.  Internally, most affected fish had a chylous effusion, congested spleens, pale proximal intestines where the blood vessels were prominent, multiple intestinal intussusceptions, and a reticular pattern to the liver due to vascular congestions.  Bacterial culture and viral isolation were attempted, but produced negative results.  Histopathological examination of these fish was also unrewarding and did not provide an adequate explanation for the massive mortalities.  To assist in furnishing an identity for this disease, the name Spring Mortality of Foodfish and Broodfish was suggested.  However, this became inappropriate because the disease recurred later that fall during cooler temperatures and it has recurred every spring and fall since 1998, usually with similar devastating effects.  This syndrome was renamed Visceral Toxicosis of Catfish when it became apparent that a toxic etiology was involved.  A more complete history of the investigative efforts that elucidated the cause of this disease and our current research efforts are described.  Return to 28th Annual Eastern Fish Health Workshop Return to Leetown Science Center Home Page