Venezuelan equine encephalitis (VEE) virus is a mosquito-borne pathogen that has caused encephalitis in equine species and humans during sporadic outbreaks in the western hemisphere. The last, and most widespread, VEE outbreak occurred in South America, Central America, Mexico and the U.S.A. (Texas) during 1969 to 1972. We have cloned and sequenced the genome of a virulent VEE subtype I-AB virus, strain 71-180, isolated in Texas in 1971. Thirty-four nucleotide differences were detected between the genome of 71-180 virus and that of the subtype I-AB Trinidad donkey (TRD) virus isolated during the 1943 VEE epizootic in Trinidad. Fifteen nucleotide changes occurred in the non-structural genes, 16 in the structural genes and three in the 3′ non-coding region. Only six of the nucleotide differences resulted in amino acid substitutions: one change in each of non-structural proteins nsP1 and nsP3, two in the E2 envelope glycoprotein, one in the 6K polypeptide and one in the E1 envelope glycoprotein. The close genetic relationship between 71-180 virus and TRD virus, commonly used for production of formalin-inactivated VEE vaccines, suggests that incompletely inactivated virulent vaccine virus may have been the source of this and other VEE outbreaks. Use of formalized virulent virus was discontinued during the 1969 to 1972 panzootic. No VEE epizootics have been reported since the introduction of the live attenuated TC-83 vaccine virus.


Article metrics loading...

Loading full text...

Full text loading...


Most cited this month Most Cited RSS feed

This is a required field
Please enter a valid email address
Approval was a Success
Invalid data
An Error Occurred
Approval was partially successful, following selected items could not be processed due to error