DIAGNOSTIC-FINDINGS IN THE 1992 EPORNITIC OF NEUROTROPIC VELOGENIC NEWCASTLE-DISEASE IN DOUBLE-CRESTED CORMORANTS FROM THE UPPER MIDWESTERNUNITED-STATES

Neurotropic velogenic Newcastle disease (NVND) occurred in juvenile do uble-crested cormorants, Phalacrocorax auritus, simultaneously in nest ing colonies in Minnesota, North Dakota, South Dakota, and Nebraska an d in Lakes Michigan, Superior, Huron, and Ontario during the summer of 1932. Mortality as high as 80%-90% was estimated in some of the nesti ng colonies. Clinical signs observed in 4- to -6wk-old cormorants incl uded torticollis, tremors, ataxia, curled toes, and paresis or weaknes s of legs, wings or both, which was sometimes unilateral. No significa nt mortality or unusual clinical signs were seen in adult cormorants. Necropsy of 88 cormorants yielded no consistent gross observations. Mi croscopic lesions in the brain and spinal cord were consistently prese nt in all cormorants from which Newcastle disease virus (NDV) was isol ated. Characteristic brain lesions provided rapid identification of ne w suspect sites of NVND. Lesions were also present in the heart, kidne y, proventriculus, spleen, and pancreas bur were less consistent or no nspecific. NDV was isolated at the National Wildlife Health Center fro m 27 of 93 cormorants rested. Virus was most frequently isolated from intestine or brain tissue of cormorants submitted within the first 4 w k of the epornitic. Sera collected from cormorants with neurologic sig ns were consistently positive for NDV antibody. The NDV isolate from c ormorants was characterized as NVND virus at the National Veterinary S ervices Laboratories, Ames, Iowa. The NVND virus was also identified a s the cause of neurologic disease in a North Dakota turkey hock during the summer of 1992. Although no virus was isolated from cormorants re sted after the first month of submissions, brain and spinal cord lesio ns characteristic of NVND were observed in cormorants from affected si res for 2 mo, at which time nesting colonies dispersed and no more sub missions were received. Risk to susceptible populations of both wild a vian species and domestic poultry makes early recognition and confirma tion of NVND in wild birds a priority.