Equine Health

Vesicular Stomatitis

Vesicular Stomatitis Virus (VSV) is a viral disease that primarily affects horses and cattle. VSV can also affect sheep, goats, llamas, alpacas, swine, deer and some other species, including bobcats, raccoons and monkeys. Humans can also become infected with the disease when handling affected animals, but this is a rare event. Vesicular Stomatitis has been confirmed only in the Western Hemisphere. It is known to be an endemic disease in the warmer regions of North, Central, and South America, but outbreaks of the disease in other temperate geographic parts of the hemisphere occur sporadically.


Anthrax is a naturally occurring disease affecting deer, cattle, exotic livestock, horses, swine, dogs and humans. It is caused by Bacillus anthracis; a spore-forming bacteria. The bacteria can remain alive, but dormant in the soil for several years.

Anthrax is found worldwide, but in Texas, cases are most often confined to a triangular area bound by the towns of Uvalde, Ozona and Eagle Pass. This area includes portions of Crockett, Val Verde, Sutton, Edwards, Kinney and Maverick Counties.

Equine Herpesvirus-1

Equine Herpes Myeloencephalopathy (EHM) is a neurologic disease of horses linked to the Equine Herpes Virus (EHV-1). EHV-1 in horses can cause respiratory disease, abortion, and neonatal death. Neurological signs appear as a result of damage to blood vessels in the brain and spinal cord. EHV-1 is a reportable disease to the Texas Animal Health Commission.


Equine piroplasmosis is a blood-borne parasitic disease of horses and other equidae. This disease is reportable to the TAHC and all positive equine in the state are under quarantine. Research into treatment options is ongoing at a national level.

A number of states, national and in-state events, and racetracks have imposed specific entry requirements related to piroplasmosis. Owners and veterinarians are urged to directly contact the state of destination or event organizer before moving horses.

Equine Infectious Anemia

Equine infectious anemia (EIA) is an incurable, infectious disease caused by a virus that can affect horses, donkeys, asses and other equine. This virus destroys red blood cells and is spread through blood-to-blood contact, not through close proximity or casual contact. The virus can be transmitted from an infected equine to a "clean" equine by biting flies, the use of unsterilized or contaminated medical instruments, or through a blood transfusion. This disease does not affect humans.

Eastern, Western, and Venezuelan Equine Encephalitis

Eastern, Western, and Venezuelan Equine Encephalitis are reportable diseases to the TAHC.

Eastern equine encephalomyelitis (EEE) is a mosquito-borne viral disease of all equine species. Infected horses may suddenly die or show progressive central nervous system disorders. Symptoms may include unsteadiness, erratic behavior and a marked loss of coordination.

Western equine encephalomyelitis (WEE) is a viral disease that mainly affects horses; mosquitoes primarily transmit this disease. Similar to EEE, WEE is characterized by central nervous system dysfunction.

Venezuelan equine encephalomyelitis (VEE) is a viral disease that affects horses and causes illness in humans. It has not been seen in the United States for many years (however, a recent outbreak of VEE occurred in Mexico). Mosquitoes most often transmit the disease after the insects have acquired the virus from birds and rodents. Humans also are susceptible when bitten by an infected mosquito, but direct horse-to-horse or horse-to-human transmission is very rare. Symptoms in horses vary widely, but all result from the degeneration of the brain. Early signs include fever, depression and appetite loss.

For more information on mosquito borne diseases visit— AAEP Horse Health

Fever Ticks

All Fever tick information is now located on the TAHC Fever Ticks & Pests page.

West Nile Virus

West Nile Virus, is a potentially deadly disease that can affect horses and humans. Like Eastern Equine Encephalitis (EEE), Western Equine Encephalitis (WEE), Venezuelan Equine Encephalitis (VEE,) West Nile virus is transmitted to horses via the bite of an infected mosquito. While not a reportable disease to the TAHC, it is recommended that horse owners consult with their veterinarian about protecting their horses against this mosquito-borne illness as well.

Glanders Disease

Glanders is a highly contagious, bacterial disease of the equine family. The disease is characterized by the development of ulcerating growths that are most commonly found in the upper respiratory tract, lungs, and skin. Infections are usually fatal. Humans and other animals are also susceptible.

The disease is commonly contracted by consuming food or water contaminated by the nasal discharge of carrier animals. The organism can survive in a contaminated area for more than one year, particularly under humid, wet conditions.

There is no vaccine for Glanders. Prevention and control depend on early detection and the elimination of affected animals, as well as complete quarantine.

Glanders was once prevalent worldwide, but has been eradicated or effectively controlled in many countries, including the United States. The last naturally occurring equine case in the U.S. was in 1942.