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Horses have lived and worked alongside people for thousands of years.  Since the advent of industrialization, horses have shifted from being used for transportation and agriculture to companions for many people, enriching their lives and leisure.

However, horses can carry diseases that can make people sick.  It is important to wash your hands after cleaning stalls, grooming horses, or picking up their feet to reduce your risk of getting sick.

What horse-related diseases are of concern in Ohio?

Animal bites: horses

Although horse bites are uncommon, they can become infected and pose a risk of transmission for rabies.

If you have been bitten by a horse, consult with your healthcare provider regarding the need for antimicrobial treatment, and report the bite to your local health department.

Equine encephalitis viruses

HorsesEquine encephalitis viruses include three viruses that can infect both horses and people:

  • Eastern equine encephalitis virus, the only of these to occur naturally in Ohio, is most commonly found in the eastern United States and Canada.
  • Western equine encephalitis virus has been identified in North and South America; in the United States, it is diagnosed most commonly west of the Mississippi River.
  • Venezuelan equine encephalitis virus occurs primarily from Mexico south into Central and South America, although rare cases have been identified in the southern United States.

All three viruses are spread through mosquito bites and cause similar symptoms.  In horses, symptoms can include fever, lethargy, behavioral changes, and incoordination.  Fatality rates for Eastern equine encephalitis and Venezuelan equine encephalitis can approach 90 percent in horses.

Symptoms in people include fever, body and joint aches, headache, and disorientation.

A vaccine is available for horses to protect them from these viruses.  Prevention for people includes avoiding mosquito bites by using insect repellent, wearing protective clothing, and eliminating mosquito breeding sites.


Leptospirosis is caused by Leptospira interrogans bacteria.  It can infect people and a wide range of domestic and wild animals, including horses.

Leptospira is shed in the urine of infected animals.  Transmission usually occurs through exposure to water or soil that has been contaminated with Leptospira bacteria, although transmission can also occur through direct contact with urine from an animal shedding the bacteria.


Rabies virus can infect any species of mammal.  It causes encephalitis and is almost always fatal once symptoms develop.  It is spread when a person or animal is bitten by an infected animal or, less commonly, when saliva from an infected animal gets into an open wound or onto a mucous membrane.

All bites should be reported to the local health department.

Protect your horses by having them vaccinated for rabies.  If you suspect your horse may have rabies, contact your veterinarian and the Ohio Department of Agriculture.


Salmonellosis is a gastrointestinal illness of humans and animals caused by Salmonella bacteria.  The most common source of infection for humans is through ingestion of food contaminated with Salmonella bacteria.

Horses infected with Salmonella may develop diarrhea, although some horses can shed the bacteria in their stool without apparent signs of infection.  One strain of Salmonella, serotype Abortusequi, can cause abortions in pregnant mares and arthritis in foals.

Hand washing and proper food handling techniques are important ways of preventing human infections.

West Nile virus

Horses are at high risk of contracting and dying from West Nile virus.  Horses infected with West Nile virus develop fever, weakness, and incoordination.

West Nile virus is spread by mosquitoes.  It was first found in Africa in 1937, but it did not appear in the United States until 1999.  After being discovered in New York where it killed birds at a zoo and infected people, it spread westward across the United States and Canada.

Birds are the natural host for West Nile virus.  Humans and horses become infected from mosquitoes that have fed on infected birds.  You cannot get West Nile virus from a horse.

People with the virus may have no symptoms, or they may have illness ranging from mild to severe.  In the severe forms, West Nile virus affects the nervous system and may result in disability, paralysis, or death.

A vaccine is available for horses to protect them from West Nile virus.  Prevention for people and horses should also include avoiding mosquito bites by using insect repellents, wearing protective clothing, and eliminating mosquito breeding sites.