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Health and Disease Information

Equine Infectious Anemia

Equine Infectious Anemia (EIA) affects the immune system of horses, ponies, mules, donkeys, asses and zebras. The disease spreads when blood from infected animals is transmitted to other animals by blood-sucking insects or through the use of contaminated hypodermic needles or surgical instruments. No treatment is available. Infected animals must be freeze-branded, sent to market, euthanized, or quarantined for life.

Animal health officials enforce regulations requiring a negative test for EIA within 12 months preceding entry into the state or participation in an advertised equine event. These events include shows, demonstrations, sales, auctions, rodeos, and organized trail rides. State law also mandates testing of Equidae within 1½ miles of a single positive animal and 3 miles of multiple positive animals.

All equine 12 months of age and older moving through sales and auctions are required to have a negative test for EIA within 12 months prior to arrival at the sale. Equine being loaned, leased, traded, or sold privately are also required to have tested negative within the preceding 12-month period if the animal is more than 12 months of age. Visit the above link for more information. 

Equine Herpesvirus

Equine Herpes Virus (EHV-1) impacts horses and can cause respiratory disease, abortion in mares, neonatal foal death, and/or neurologic disease. The virus can spread through the air, contaminated equipment, clothing, and hands. According to the University of Kentucky Equine Research Center, the virus's ability to reside as a silent and persistent infection in horses provides for continual transmission. It is vital that good biosecurity measures be implemented on exposed premises.

Horse owners need to be mindful that most horses are exposed to one or more strains of EHV at a very young age.  Periods of high stress or additional exposure may cause an animal to exhibit clinical signs of disease.  Occasionally, the disease is exhibited as a serious neurologic disease.  Owners should consult with their veterinarian when deciding whether or not to attend an equine event as anytime horses are commingled there is the opportunity for exposure.

The United States Department of Agriculture Animal and Plant Health Inspection Service (USDA APHIS) states, the incubation period of EHV-1 is 1-10 days; typically signs are seen within 1-3 days post-exposure. Viral shedding occurs for 7-10 days but can occur up to 28 days from the onset of signs.

The neurologic signs include ataxia, urinary bladder atony, and reduced tail tone. In severe cases, horses will be unable to stand; these cases have a very poor prognosis. Foals are rarely affected with the neurologic form of EHV-1, and no sex predilection is seen. Treatment is supportive and tailored to the specific case. 

Once a horse is infected, it should be quarantined.  USDA recommends isolating and monitoring of all exposed horses for at least 7 days. During the isolation period, it is recommended to discontinue or reduce any strenuous training or exercise for exposed horses. 

All exposed horses should have rectal temperatures taken twice daily (8-12 hours apart) and recorded in a log for at least 7 days after the date of potential exposure. Horses whose rectal temperature registers higher than 101.5 degrees Fahrenheit are considered to be febrile. All horses on the premises should also be monitored for neurologic signs (ataxia, posterior incoordination, weakness, recumbency with inability to rise, circling, head pressing, head tilt, bladder atony) during the home quarantine period. Central nervous system signs, such as posterior incoordination, weakness, recumbency with the inability to rise, and bladder atony are most common in EHV-affected horses. 

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West Nile Virus

West Nile virus first emerged in the United States in the New York metropolitan area in the fall of 1999. Since then, the virus, which can be transmitted to humans by the bite of an infected mosquito, has quickly spread across the country.  To report a suspected or confirmed case of the West N​ile Virus, call the Bureau of Animal Health and Welfare, Monday through Friday from 8:00 AM to 4:30 PM, at (217) 782-4944 to provide case information.

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Reportable Diseases
See a list of all reportable diseases of livetsock at the linke above.


Biosecurity is the process of protecting farms and livestock from infectious diseases.  Horse owners should create and carry out biosecurity plans specific to their farms.  Diseases can be introduced in many ways and a good plan addresses all known routes of disease transmission. These plans and procedures include vaccination strategies, and biosecurity in your barn, while traveling, at events, and when caring for your horse.  They are critical to maintaining the health of all horses regardless of their occupation.   

The Equine Disease Communication Center is a great source of information on biosecurity for horses.  This site has a video from US Equestrian as well as a toolkit and guidance for events, facilities, travel, and much more.  You can also visit the American Association of Equine Practitioners page for their recommendations for a biosecurity program.  

Additional Topics

  • Imports - go here for information on the requirements for entering Illinois 
  • Animal Disease Traceability (ADT)  
    • Information on individual official animal identification with a link to the USDA ADT website as well as USDA approved animal identification methods. 
    • Premises Identification - premises identification is voluntary, however during an animal health emergency this information is critical to efficient notification and response.  
  • Emergency Preparedness 
    • Information for livestock owners on emergency and disaster preparedness

More Equine Resources