A COMPARISON OF THE INFECTION DYNAMICS OF COTTON RATS AND HOUSE SPARROW WITH NORTH AND SOUTH AMERICAN EASTERN EQUINE ENCEPHALITIS VIRUS

Nicole C. Arrigo¹, D.M. Watts, Ph.D.², P.C. Newman¹, S.C. Weaver, Ph.D.¹

¹Department of Pathology UTMB; ²UT El Paso, El Paso, TX

Background: The Eastern Equine Encephalitis (EEE) antigenic complex (genus Alphavirus, family Togaviridae) includes 4 major EEEV subtypes; three circulate in Central/ South America (SAEEEV) and are associated with equine disease, and one occurs in North America (NAEEEV) and is associated with severe human and equine neurological disease. Despite their known geographic and epidemiologic dichotomy, the extent of their ecological differences remains unclear. Objective: In order to clarify the role of mammalian and avian species in the transmission of SAEEEV, the infection dynamics of cotton rats (Sigmodon hispidus) and house sparrow (Passer domesticus) with NA and SAEEEV were compared. Methods: Multiple cohorts of each species were inoculated with one of three EEEV viruses: FL93-939 (NAEEEV), C-49 (SAEEEV), or PE70 77U1104 (SAEEEV). Animals were bled daily for 7 days or until moribund and the viremia and antibody profiles determined. Results: Viremia levels of SAEEEV PE70 were consistently higher in cotton rats, while those of NAEEEV were consistently higher in house sparrow. NAEEEV generally resulted in high mortality rates in all adult animals. Alternatively, SAEEEV resulted in no death or observable illness in cotton rats and intermediate levels in house sparrow. Conclusions: These results suggest that, although both cotton rats and house sparrow are capable of serving as competent hosts for both NA and SAEEEV, Sigmodon hispidus, and potentially other ground-dwelling mammals, may be better adapted to serve as reservoirs hosts in the enzootic transmission of SAEEEV. NCA was supported by the NIH-sponsored Biodefense Training Program (T32-AI060549) and the project by NIAID-WRCE grant U54 AI057156 (to SCW).