[Post-epizootic activity of Western equine encephalitis virus in Argentina]

It is shown here the WEE virus activity in ARgentina in 1983-1986 post-epizootic period. A surveillance system was established by the equine case notification and the sentinel animal method. Among the thirteen equine focus notified between September 1983-September 1985 in Córdoba and Santa Fe Provinces, 5 presumptive cases out of 16 sick horses were confirmed by the hemagglutination inhibition test for WEE epizootic virus. Twenty eight notified human cases were studied with negative results. The neutralizing antibody (Ac NT) prevalence among sentinel horses in Córdoba Province (4%) was lower than that of Santa Fe Province (13%) in April, 1984. It was shown that Ac NT disappeared in a 12-month period in 40% of the Santa Fe horses. Two seroconversions in Córdoba (12/1983 to 4/1986) and 9 seroconversions in Santa Fe (2/1984 to 7/1986) were registered. One of the sentinel horses form Córdoba Province also seroconverted with the enzootic WEE AG 80-646 virus. Due to the recognized cross-antigenicity between both viruses, reactivity was attributed to WEE epizootic virus. No viral activity was detected in the domestic birds. With this contribution, the study of one epizootic cycle of WEE virus was completed: pre-epizootic silence (1977-1980), epizootic (1982-1983) and residual focus plus inapparent infections during a post-epizootic period (1983-1986).