VENEZUELAN EQUINE ENCEPHALOMYELITIS

Venezuelan equine encephalomyelitis (VEE) is another threatening disease caused by a virus similar to the one that causes eastern equine encephalomyelitis. VEE stems from several different subtypes of the virus, each of which produces different signs of illness. Mortality rates range from 30 to 90 percent, depending on the virulence of the strain of virus.

The disease is usually found only in South America, but it can creep northward into Central America and Mexico. The good news is that VEE hasn’t appeared in the United States since an outbreak occurred in southern Texas in 1971. However, the possibility that the disease could arrive in the United States again remains a risk.

One factor that would make a VEE outbreak even more alarming is that horses are not dead-end hosts for the virus. Mosquitoes and other biting insects could pick up the virus from an infected horse and spread it to others—which would enable a potential outbreak to move very quickly through local herds.

Vaccines against VEE are not currently recommended for use in the United States, in part because horses who already have antibodies to the virus would confuse testing should an outbreak occur. It’s possible that the current EEE/WEE vaccine provides some crossprotection against VEE, and should an outbreak occur in the States, a VEE vaccine would also likely be made available.