Identification of Two South American Strains of Eastern Equine Encephalomyelitis Virus From Migrant Birds Captured on the Mississippi Delta1

Calisher, C. H. (CDC, Atlanta, Ga. 30333), K. S. C. Maness, R. D. Lord and P. H. Coleman. Identification of two South American strains of eastern equine encephalomyelitis virus from migrant birds captured on the Mississippi delta. Amer J Epidem 94: 172–178, 1971.—Eastern equine encephalomyelitis (EEE) virus isolates were obtained from two migrant birds, a blackpoll warbler and a woodthrush, captured at the time these species were migrating into southern Louisiana in 1966. Using a timed hemagglutination-inhibition technique, we cross-compared these isolates with four established and 11 recent EEE virus isolates from North, Central, and South Americas. In three replicate experiments the two isolates from the migrant birds captured in Louisiana were shown to be South American serotypes. Although a number of studies were performed to determine variances which might be due to time of incubation and/or antibody unitage, tests showing the antigenic relationships were reproducible. These findings constitute the first serologic evidence in support of trans-Gulf transport of EEE virus. Possible epidemiologic and ecologic implications of these findings are discussed.