After nearly five years of being VS free, Vesicular Stomatitis is exploding across large areas of Texas with the count up to nine counties with confirmed cases this year, mostly in equine. The latest confirmations include two cases of bovine infection as well.

On July 30 the Texas Animal Health Commission reported 14 new premises have been found with one or more animals confirmed with Vesicular Stomatitis virus (VSV), all but one in Central Texas, including 12 premises in Bastrop County and one additional premise in Travis County. The remaining premise was located in Val Verde County near Del Rio.

On July 25 eight new cases of VSV were reported in Central Texas, including five premises in Travis County and three new premises in Bastrop County.

The latest round of confirmed premises raises the total number reported this year to 35 sites. Affected counties include: Kinney, Hidalgo, San Patricio, Nueces, Jim Wells, Bastrop, Travis, Guadalupe and Val Verde counties. Six premises have been released from quarantine: one in Kinney County, two in Nueces County, two in San Patricio County and one in Hidalgo County.

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Large number susceptible

According to the USDA-APHIS weekly VS update, so far this year 50 horses and four head of cattle have tested positive for VS New Jersey serotype. Forty of those animals remain in quarantine while 10 have recovered.

A large number of other animals in Texas have been or remain susceptible to VS infection according to the USDA-APHIS report, including 388 horses, 1,855 cattle, three pigs, and 30 goats. These numbers include all infected animals so far this year.

Also of major concern are reports coming out of Colorado where confirmed VS cases are on the rise. Colorado animal health officials are reporting a total of 37 horses across four counties have tested positive for VS over the last 10 days, representing the first cases reported outside of Texas this year.

Infected animal are quarantined for a period of no less than 21 days and monitored by state animal health officials. After the quarantine expires, and provided the animals show no further symptoms or signs of VS, the premise is released from quarantine.

Animal health officials offer no particular reason why this year's outbreak of VS has occurred so fast and in such large numbers. Phlebotomine sandflies, which have been confirmed biological vectors of VSV, can spread the virus, but of most concern in the Southwest are Culicoides midges and Simulium blackflies.

However, VSV can also be spread by direct contact between infected animals and also through watering and feed troughs and buckets. While rare, human contact with an infected animal can transfer the virus to humans and to other animals; the virus is much less severe in humans and generally causes only flu-like symptoms.