Venezuelan Equine Encephalitis (VEE) Confirmed in Mexico

August 20th, 2011 10:59 AM | No Comments

Press Release

Equine owners encouraged to consult with veterinarian

AUSTIN – Due to recent cases of Venezuelan Equine Encephalitis (VEE) in Southern Mexico, horse owners and veterinarians are encouraged to be alert to any clinical signs of illness that could indicate VEE. Venezuelan Equine Encephalitis (VEE) is a non-contagious viral infection of horses and other equids that can cause a severe and often fatal encephalitis/encephalomyelitis, which is defined as an inflammation of the brain and spinal cord.

VEE is typically found in Central and South America, but due to the recent case of a horse that died of VEE in Southern Mexico, the United States Department of Agriculture (USDA) issued an import alert for four states in Mexico. Effective immediately, and until further notice, horses and other equids from the states of Tamaulipas, Veracruz, Tabasco, and Chiapas or that have transited through these states are required to undergo a 7-day quarantine and observation for VEE in a vector-proof (double-screened) quarantine facility, rather than the standard 3-day quarantine prior to entry into the U.S. The particular VEE virus being reported by Mexico is considered an endemic strain, which doesn’t normally cause disease in equids. The import alert issued by USDA is a precautionary measure due to the one horse in the State of Tabasco that has died from the virus. The severe outbreak that occurred in Texas in 1971 was caused by a different, more virulent strain of the virus.

Clinical signs of VEE include moderate to high fever, depression, lack of appetite, cranial nerve deficits (facial paralysis, tongue weakness, difficulty swallowing), behavioral changes (aggression, self-mutilation, or drowsiness), gait abnormalities, or severe central nervous system signs, such as head-pressing, circling, blindness, and seizures.
VEE is usually transmitted by mosquitoes, and infrequently by other bloodsucking insects. People may also be infected by mosquitos, but horse-to-horse and horse-to-human transmission is uncommon. VEE is highly pathogenic in horses. It can also cause illness in humans.

VEE is a foreign animal disease, reportable to both the TAHC and the Department of State Health Services due to the potential for human illness. Vaccination may interfere with testing for the disease, so veterinarians need to weigh the potential risks and benefits of vaccinating an individual horse that might be tested for export.

“There have been no reported cases of VEE in recent years in Texas. However, our close proximity to Mexico means that we will be keeping a close eye on any cases across the border and determining whether any further regulatory action will be needed,” said Dr. Andy Schwartz, TAHC State Epidemiologist. “Vaccination and other protective measures for all equine including West Nile Virus, Western and Eastern Equine Encephalitis (WEE/EEE) should be discussed with your veterinarian.”

  • Click here for more information about VEE
  • Click here for the American Association of Equine Practitioner VEE vaccination guidelines
  • Click here for import requirements

Founded in 1893, the Texas Animal Health Commission works to protect the health of all Texas livestock, including: cattle, swine, poultry, sheep, goats, equine animals, and exotic livestock.


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