Diagnostic Findings in the 1992 Epornitic of Neurotropic Velogenic Newcastle Disease in Double-Crested Cormorants from the Upper Midwestern United States

Abstract

Neurotropic velogenic Newcastle disease (NVND) occurred in juvenile double-crested cormorants, Phalacrocorax auritus, simultaneously in nesting colonies in Minnesota, North Dakota, South Dakota, and Nebraska and in Lakes Michigan, Superior, Huron, and Ontario during the summer of 1992. Mortality as high as 80%-90% was estimated in some of the nesting colonies. Clinical signs observed in 4- to 6-wk-old cormorants included torticollis, tremors, ataxia, curled toes, and paresis or weakness of legs, wings or both, which was sometimes unilateral. No significant mortality or unusual clinical signs were seen in adult cormorants. Necropsy of 88 cormorants yielded no consistent gross observations. Microscopic lesions in the brain and spinal cord were consistently present in all cormorants from which Newcastle disease virus (NDV) was isolated. Characteristic brain lesions provided rapid identification of new suspect sites of NVND. Lesions were also present in the heart, kidney, proventriculus, spleen, and pancreas but were less consistent or nonspecific. NDV was isolated at the National Wildlife Health Center from 27 of 93 cormorants tested. Virus was most frequently isolated from intestine or brain tissue of cormorants submitted within the first 4 wk of the epornitic. Sera collected from cormorants with neurologic signs were consistently positive for NDV antibody. The NDV isolate from cormorants was characterized as NVND virus at the National Veterinary Services Laboratories, Ames, Iowa. The NVND virus was also identified as the cause of neurologic disease in a North Dakota turkey flock during the summer of 1992. Although no virus was isolated from cormorants tested after the first month of submission, brain and spinal cord lesions characteristic of NVND were observed in cormorants from affected sites for 2 mo, at which time nesting colonies dispersed and no more submissions were received. Risk to susceptible populations of both wild avian species and domestic poultry makes early recognition and confirmation of NVND in wild birds a priority.

The 1992 Epizootic of Newcastle Disease in Double-Crested Cormorants in North America

“…Necropsy findings have previously been reported in a subset of American cormorants from this epizootic (Banerjee et al, 1994;Meteyer et al, 1997) and no consistent significant gross lesions were found in the additional DCC reported here, from the USA or Canada. Newcastle disease virus was isolated from birds from 15 USA colony sites in Minnesota, Nebraska, North Dakota and South Dakota, Lake Superior, Lake Michigan, Lake Huron and Lake Ontario (Table 1).…”

“…For each DCC colony, we tabulated estimated mortality (number of dead juveniles/estimated juvenile population) and presence/absence of clinical signs compatible with ND, microscopic lesions characteristic of ND in DCC (Wobeser et al, 1993;Banerjee et al, 1994;Meteyer et al, 1997), seropositive birds, and virus positive birds (Tables 1, 2).…”

“…Clinical signs in sick birds suggested neurological disease and NDV was isolated from affected cormorants and characterized, and associated lesions were described (Heckert, 1993;Banerjee et al, 1994;Heckert et al, 1996;Meteyer et al, 1997). The 1992 event is the first recorded outbreak of neurotropic FIGURE 1.…”

Causes of Morbidity and Mortality and Their Effect on Reproductive Success in Double-Crested Cormorants From Saskatchewan

“…Newcastle disease caused high mortality in cormorant chicks in , 1992, and 1995(Wobeser et al, 1993Meteyer et al, 1997;Kuiken et al, 1998). However, without estimates of mortality rates from other causes, it was not possible to assess the relative importance of Newcastle disease to these cormorant populations.…”

“…Last-hatched chicks in broods of three or four commonly die of starvation due to non-aggressive sibling competition (Hunt and Evans, 1997). Mortality from Newcastle disease, which generally occurs after chicks have left their nests, was estimated at 10 to 90% of young of the year (Meteyer et al, 1997;Kuiken et al, 1998).…”