What Horse Owners Need to Know About Equine Infectious Anemia Virus

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Equine Infectious Anemia Virus (EIAV) is a potentially fatal disease affecting horse, donkey, and mule populations. The virus continues to plague equine owner and veterinary diagnostics companies alike as no vaccine or cure is yet available. EIAV also causes anemia and inflammation that can damage vital organs. In addition, secondary infections such as pneumonia may occur due to the resulting immunosuppression caused by the virus. Affected horses can die from secondary infections or the virus itself.

Most horses are inapparent carriers, meaning they’ll show no overt signs of infection. These carriers will often have lower concentrations of the virus in their blood than horses with active signs of the disease. Inapparent carriers can survive with the infection for extended periods of time. This can pose a serious threat to other horses as only one-fifth teaspoon of EIAV blood when drawn during a feverish episode is enough to infect 10,000 horses. EIAV can also be transmitted in-utero from mare to foal.

Stages and Symptoms of EIAV

There are three stages of EIAV:

  1. Accute: Acute symptoms often develop within one to two weeks of exposure. It can be difficult for veterinary diagnostics companies to accurately diagnose a horse in the acute stage as antibodies and anemia won’t be present during the acute phase. That doesn’t mean the virus isn’t still active, though: it’s multiplying in the infected horse’s white blood cells and damaging her organs and immune system. Death will typically result within two to three weeks of the start of the acute stage.
  2. Chronic: If your horse survives the acute stage of EIAV, she may enter a chronic or subacute phase. This is when you’re most likely to see the classic symptoms of the virus, such as anemia, weight loss, fever, and depression. It’s common for repeated flare-ups of these symptoms to occur during periods of stress or when corticosteroids are administered.
  3. Inapparent: As mentioned above, most horses live in the inapparent stage. This is the stage following the chronic phase when flare-ups decrease in severity and frequency. Over the course of a year, your horse’s body may find a way to control the disease. Despite showing no symptoms, inapparent carriers are infected for life and can still infect other horses.

The symtoms of EIAV include:

  • Anemia
  • Rapid and unexplained weight loss
  • Decreased appetite
  • Fever
  • Depression
  • Swelling of the abdomen, lower chest, and legs
  • Fatigue
  • Sweating
  • Elevated breathing
  • Irregular or weak pulse
  • Nasal bleeding
  • Colic

How to identify EIAV

Veterinary diagnostics companies can determine if a horse is infected with the virus through an Equine Infectious Anemia Virus antibody test. Your horse’s blood can be tested for antibodies using agar gel immunodiffusion (AIGD), also known as the Coggins test, or a competitive enzyme linked immunoabsorben assay (C-ELISA) test. A positive result on either test signals a horse who has the virus.

The Coggins or AIGD test remains the preferred method. C-ELISA tests are popular for their rapid results. They run a higher risk of providing false-positives, however. As such, any positive results derived from a C-ELISA test should be double-checked by veterinary diagnostics companies through a Coggins test.

Treatment of EIAV

Sadly, there remains no effective treatment for Equine Infectious Anemia Virus. The good news is proper management can greatly reduce your horses’ chances of infection. Here are some guidelines to help keep your herd safe:

  • Use a veterinary diagnostics company to test all horses annually. Horses who frequently travel or are known to have been in an area where there was an outbreak should be tested more often. Also have any new horses tested before being brought home.
  • Even after testing, quarantine all new horses for 45 days and watch for signs of the virus. After a 45-day quarantine, have the horse retested by a veterinary diagnostics company.
  • Never reuse needles and syringes.
  • Sterilize all dental tools and instruments between use on horses.

What to do for infected horses

Once a horse has been positively identified as infected, there are really only two options available: euthanasia or life-long quarantine. While the latter is far more emotionally difficult, it remains the recommended course by the American Association of Equine Practitioners and federal and state health agencies. Life-long quarantine is an alternative, but it’s one that requires vigilance. Unfortunately there is no easy answer for owners of EIAV infected horses.