Research Articles

Association of Venezuelan equine encephalitis virus subtype IE with two equine epizootics in Mexico

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.

This article has been cited by other articles:

				A. C. Moncayo, G. Lanzaro, W. Kang, A. Orozco, A. Ulloa, J. Arredondo-Jimenez, and S. C. Weaver Vector Competence of Eastern and Western Forms of Psorophora columbiae (Diptera: Culicidae) Mosquitoes for Enzootic and Epizootic Venezuelan Equine Encephalitis Virus Am J Trop Med Hyg, March 1, 2008; 78(3): 413 - 421. [Abstract] [Full Text] [PDF]

				H. NI, N. E. YUN, M. A. ZACKS, S. C. WEAVER, R. B. TESH, A. P. T. DA ROSA, A. M. POWERS, I. FROLOV, and S. PAESSLER RECOMBINANT ALPHAVIRUSES ARE SAFE AND USEFUL SEROLOGICAL DIAGNOSTIC TOOLS Am J Trop Med Hyg, April 1, 2007; 76(4): 774 - 781. [Abstract] [Full Text] [PDF]

				L. L. COFFEY and S. C. WEAVER SUSCEPTIBILITY OF OCHLEROTATUS TAENIORHYNCHUS AND CULEX NIGRIPALPUS FOR EVERGLADES VIRUS Am J Trop Med Hyg, July 1, 2005; 73(1): 11 - 16. [Abstract] [Full Text] [PDF]

				I. P. GREENE, S. PAESSLER, M. ANISHCHENKO, D. R. SMITH, A. C. BRAULT, I. FROLOV, and S. C. WEAVER VENEZUELAN EQUINE ENCEPHALITIS VIRUS IN THE GUINEA PIG MODEL: EVIDENCE FOR EPIZOOTIC VIRULENCE DETERMINANTS OUTSIDE THE E2 ENVELOPE GLYCOPROTEIN GENE Am J Trop Med Hyg, March 1, 2005; 72(3): 330 - 338. [Abstract] [Full Text] [PDF]

				A. C. Brault, A. M. Powers, D. Ortiz, J. G. Estrada-Franco, R. Navarro-Lopez, and S. C. Weaver Venezuelan equine encephalitis emergence: Enhanced vector infection from a single amino acid substitution in the envelope glycoprotein PNAS, August 3, 2004; 101(31): 11344 - 11349. [Abstract] [Full Text] [PDF]

				M. Anishchenko, S. Paessler, I. P. Greene, P. V. Aguilar, A.-S. Carrara, and S. C. Weaver Generation and Characterization of Closely Related Epizootic and Enzootic Infectious cDNA Clones for Studying Interferon Sensitivity and Emergence Mechanisms of Venezuelan Equine Encephalitis Virus J. Virol., January 1, 2004; 78(1): 1 - 8. [Abstract] [Full Text] [PDF]

				S. P. SAHU, D. D. PEDERSEN, A. L. JENNY, B. J. SCHMITT, and A. D. ALSTAD PATHOGENICITY OF A VENEZUELAN EQUINE ENCEPHALOMYELITIS SEROTYPE IE VIRUS ISOLATE FOR PONIES Am J Trop Med Hyg, April 1, 2003; 68(4): 485 - 494. [Abstract] [Full Text] [PDF]

				E. Wang, A. C. Brault, A. M. Powers, W. Kang, and S. C. Weaver Glycosaminoglycan Binding Properties of Natural Venezuelan Equine Encephalitis Virus Isolates J. Virol., December 20, 2002; 77(2): 1204 - 1210. [Abstract] [Full Text] [PDF]

				A. C. Brault, A. M. Powers, and S. C. Weaver Vector Infection Determinants of Venezuelan Equine Encephalitis Virus Reside within the E2 Envelope Glycoprotein J. Virol., May 15, 2002; 76(12): 6387 - 6392. [Abstract] [Full Text] [PDF]

				A. C. Brault, A. M. Powers, E. C. Holmes, C. H. Woelk, and S. C. Weaver Positively Charged Amino Acid Substitutions in the E2 Envelope Glycoprotein Are Associated with the Emergence of Venezuelan Equine Encephalitis Virus J. Virol., February 15, 2002; 76(4): 1718 - 1730. [Abstract] [Full Text] [PDF]

				B. Linssen, R. M. Kinney, P. Aguilar, K. L. Russell, D. M. Watts, O.-R. Kaaden, and M. Pfeffer Development of Reverse Transcription-PCR Assays Specific for Detection of Equine Encephalitis Viruses J. Clin. Microbiol., April 1, 2000; 38(4): 1527 - 1535. [Abstract] [Full Text]