Oberste M S, Fraire M, Navarro R, Zepeda C, Zarate M L, Ludwig G V, Kondig J F, Weaver S C, Smith J F, Rico-Hesse R
Virology Division, U.S. Army Medical Research Institute of Infectious Diseases, Frederick, Maryland 21702-5011, USA.
Am J Trop Med Hyg. 1998 Jul;59(1):100-7. doi: 10.4269/ajtmh.1998.59.100.
Two outbreaks of encephalitis consistent with an etiology of Venezuelan equine encephalitis (VEE) virus occurred in equines on the Pacific coast of southern Mexico in 1993 (Chiapas State) and in 1996 (Oaxaca State). In Chiapas, there were 125 cases, of which 63 were fatal and in Oaxaca, there were 32 cases and 12 fatalities. Virus was isolated from two horses from each outbreak, including three brain isolates and one from blood. Virus isolates (93-42124, ISET-Chi93, Oax131, and Oax142) were shown by indirect immunofluorescence, hemagglutination inhibition, monoclonal antibody ELISA, and nucleotide sequencing to be VEE virus, subtype IE, a type previously thought to be equine-avirulent. Genetic characterization and phylogenetic analysis indicated that the outbreak viruses were identical or nearly identical to one another and that they were closely related to equine-avirulent IE strains from Guatemala and the Gulf coast of Mexico. In a plaque-reduction neutralization test, sera collected from healthy horses in Chiapas and Oaxaca reacted significantly better with isolate 93-42124 than with Guatemala IE isolate 68U201, suggesting that subtle genetic changes may have resulted in alteration of neutralization domains. It is not clear whether these differences may also influence equine virulence. However, renewed VEE virus subtype IE activity in Mexico, and its apparent conversion to equine virulence, underscores the need for increased surveillance, additional laboratory and epidemiologic studies in VEE-endemic regions, and possibly new vaccines.
1993年（恰帕斯州）和1996年（瓦哈卡州），墨西哥南部太平洋沿岸的马匹中发生了两起符合委内瑞拉马脑炎（VEE）病毒病因的脑炎疫情。在恰帕斯州，有125例病例，其中63例死亡；在瓦哈卡州，有32例病例，12例死亡。从每次疫情的两匹马中分离出了病毒，包括三株脑部分离株和一株血液分离株。通过间接免疫荧光、血凝抑制、单克隆抗体ELISA和核苷酸测序表明，病毒分离株（93 - 42124、ISET - Chi93、Oax131和Oax142）为VEE病毒IE亚型，该亚型以前被认为对马无毒力。遗传特征分析和系统发育分析表明，疫情病毒彼此相同或几乎相同，并且它们与来自危地马拉和墨西哥湾沿岸的马无毒力IE株密切相关。在蚀斑减少中和试验中，从恰帕斯州和瓦哈卡州健康马匹采集的血清与分离株93 - 42124的反应明显优于与危地马拉IE分离株68U201的反应，这表明细微的基因变化可能导致了中和结构域的改变。尚不清楚这些差异是否也会影响马的毒力。然而，VEE病毒IE亚型在墨西哥的重新活跃及其向马毒力的明显转变，凸显了加强监测、在VEE流行地区开展更多实验室和流行病学研究以及可能研发新疫苗的必要性。
