Trinity River Serologic Survey - Survey of Residents of Communities Along Course of Trinity River Between Houston and Dallas, Texas, for Antibodies to Viruses of St-Louis Encephalitis, Western Equine Encephalitis and California Encephalitis
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A serologic survey was performed in six communities along the course of the Trinity River between Houston and Dallas, Texas, both sites of major St. Louis encephalitis (SLE) epidemics. Blood was obtained and interviews completed on a sample of 423 persons living in these towns. Antibody studies involving the viruses of St. Louis encephalitis, Western equine encephalitis (WEE) and California encephalitis (CE) were performed. SLE neutralizing antibody prevalence for the total sample was 3.3%. Comparable figures for WEE and CE were 1.2% and 1.7%, respectively. SLE antibody prevalence was not related to sex or race nor consistently associated with residence near the Trinity River. SLE antibody prevalence was not positively correlated with residence in communities located in the thick pine forests of East Texas or with forestry as an occupation, although CE antibody rates showed such associations. To explain the survey results and in accordance with known facts concerning vectors in this area of the country, it was postulated that a part of SLE transmission to the survey population occurred as focal outbreaks within the towns and was mediated by Culex quinquefasciatus mosquitoes. It is possible that another transmission cycle, involving SLE and WEE and Culex tarsalis mosquitoes, may have been operative, at least in the past, in a portion of the area surveyed. This latter consideration was tempered by the lack of knowledge concerning Culex tarsalis in East Texas and the possible presence there of alternate vector(s) for WEE.