Experimental Infection of Birds with Epidemic Venezuelan Encephalitis Virus

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  • Vertebrate Ecology Branch, Vector-Borne Diseases Division, Bureau of Laboratories, Center for Disease Control, U.S. Public Health Service, U.S. Department of Health, Education, and Welfare, Fort Collins, Colorado 80522
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Sixty-three birds representing 13 species were inoculated with a strain of epidemic Venezuelan encephalitis (VE) virus from the 1971 Texas outbreak. More than 95% of the birds became infected. Mortality which could be attributed to infection with VE virus was very low. Viremia persisted 2–6 days. Peak viremia levels ranged from 103.2 to 108.2 suckling mouse intracranial 50% lethal doses per milliliter (SMICLD50/ml). Blood virus levels were highest in juvenile Louisiana Herons, adult Robins and adult Mockingbirds and were lowest in juvenile Common Egrets. Most bird species had blood virus levels about 105 SMICLD50/ml (high vector infection potential) for 2–3 days. Neutralizing antibody response was more uniform and frequent in herons (95%) than in passerines (56%). The role of birds in the epidemiology of Venezuelan encephalitis is discussed.