1College of Veterinary Medicine, University of Florida, Gainesville, FL, USA; 2Florida Department of Health Bureau of Laboratories, Tampa, FL, USA; 3West Orange Veterinary Hospital, Winter Garden, FL, USA; 4Division of Vector-Borne Infectious Diseases, Centers for Disease Control and Prevention, Fort Collins, CO, USA
In September and October 2002, an epizootic characterized by neurologic disease occurred at a 9,000-alligator farm in Florida. Approximately 300 alligators (Alligator mississippiensis) died during this time. First cases were observed in 1-m long yearlings on 15 October 2002. Three animals were clinically evaluated and exhibited a range of signs that included depression, lethargy and signs of neurologic disease. They were euthanatized and necropsies were performed. Gross lesions consisted of mild coelomic effusions, fibrinonecrotic oral mucosal exudates, and enlarged pale livers with red mottling. The most significant microscopic lesions were a moderate heterophilic to lymphoplasmacytic meningoencephalomyelitis, necrotizing hepatitis and splenitis, myocardial degeneration with necrosis, mild interstitial pneumonia, hepatic lipidosis, adrenalitis, and heterophilic necrotizing stomatitis, and glossitis. Examination of the brain and other tissues was conducted using an immunoperoxidase staining technique and a monoclonal antibody for West Nile virus (WNV) antigen. Positive staining was demonstrated in the brain as well as other tissues. Portions of brain, spinal cord, and other tissues were submitted both to the Florida Department of Health Bureau (FDHB) of Laboratories in Tampa and to the Division of Vector-Borne Infectious Diseases, Centers for Disease Control and Prevention (CDC) in Ft. Collins, Colorado, for definitive diagnosis of WNV. Virus was isolated, and polymerase chain reaction (PCR) testing confirmed the presence of WNV. This was the first identification of WNV in a reptile.