VIRUS OF ST. LOUIS ENCEPHALITIS IN THREE SPECIES OF WILD BIRDS1

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Abstract
English sparrows, cowbirds and red-winged blackbirds were infected with St. Louis encephalitis virus by subcutaneous inoculation and by the bite of infected Culex tarsalis mosquitoes. Viremias were low, especially in the cowbirds and red-winged blackbirds, undetectable for the most part in blood diluted 1 in 10. This amount of virus in the blood was adequate for infection of normal C. tarsalis ingesting it, however. Virus multiplication of over a million-fold in the mosquito was shown. A complete transmission cycle (chickens-C. tarsalis-wild birds-C. tarsalis-chickens) was accomplished. The antibody response of the birds was weak following SLE infection. SLE virus was isolated 38 days after infection from gizzard tissue of the cowbird but not from other organs tested.