Understanding The Threat of Equine Infectious Anemia (EIA)
Equine Infectious Anemia (EIA), also known as Swamp Fever, is an infectious disease of horses, donkeys and mules caused by a RNA virus and spread by blood-sucking insects such as horse flies, deer flies and stable flies. Horses infected with the EIA virus carry it for life. Most infected horses show no symptoms but they remain infectious, endangering the health of other horses. The best protection against EIA is to understand the disease and the control measures that can help keep your horses from contracting it.
What is Equine Infectious Anemia (EIA)?
Equine Infectious Anemia (EIA) is a viral disease that affects the horse’s immune system. The virus reproduces in the horse’s blood cells and circulates throughout the body. The horse’s immune system produces antibodies, which attack and destroy its own blood cell components. The result is anemia and organ-damaging inflammation. The clinical symptoms of EIA are variable and include fever, anorexia, depression, swelling of the underside of the belly and legs, muscle weakness and wasting, jaundice of mucous membranes and infertility. EIA can leave a horse vulnerable to other potentially fatal diseases.
Equine Infectious Anemia does not pose a risk to human health.
The Canadian Food Inspection Agency  (CFIA), in collaboration with equine stakeholders, conducts surveillance for EIA through the national EIA Control Program . Under the current program, horse owners voluntarily have their animals tested for the disease.
EIA is a reportable disease under the Health of Animals Regulations. This means that all suspected cases must be reported to the CFIA.
Phases of Equine Infectious Anemia (EIA)
Equine Infectious Anemia (EIA) has three phases:
- Acute - during this phase the virus is active, multiplying and harming the immune system. The acutely ill horse has heavy concentrations of the virus in its bloodstream.
- Chronic - the animal has high concentrations of the virus in its blood but may alternate between remission and disease states.
- Inapparent Carrier- the horse carries the virus but shows no apparent signs of illness. Stress or disease may trigger an acute episode.
At this time, there is no treatment or cure for a horse that has contracted EIA. There is also no vaccine available to protect a horse from the EIA virus.
Transmission of Equine Infectious Anemia (EIA)
Equine Infectious Anemia (EIA) is a blood-borne disease transmitted mainly through the natural feeding of large biting insects, principally horseflies and deerflies. Transmission can also occur through the re-use of contaminated needles and surgical and dental instruments. Because these processes can be identified, decisions can be made regarding disease management and control.
It is important to remember the threat that an EIA infected horse poses to the whole community. The risk may be unknown, but the consequences can be great, extending even to legal liability. Strict control measures should be followed in order to prevent the spread of this virus. All stables, farms, horse shows, racetracks, rodeos, clinics and equine event operators are strongly encouraged to ask for and verify a current Coggins certificate for all horses entering their premises. This, along with good management practices, will help in the fight against this disease. All equids infected with EIA virus remain lifelong carriers.
There is no vaccine available for equine infectious anemia. It is important to remember the threat that an EIA infected horse poses to the whole community. The risk may be unknown, but the consequences can be great, extending even to legal liability. Strict control measures should be followed in order to prevent the spread of this virus. All stables, farms, horse shows, racetracks, rodeos, riding clinics and equine event operators are strongly encouraged to ask for and verify current EIA test results for all horses entering their premises. The most common test for EIA, the agar gel immunodiffusion (or Ccoggins) test, along with rapid testing (ELISA tests), provide a high level of sensitivity to equine infectious anemia. Up-to-date testing, along with good management practices, will help in the fight against this disease.
Listed below are a number of measures one can take to prevent equine infectious anemia.
Use sterile needles, syringes, and IVs
Disinfect any tattoo equipment, surgical equipment, lip chains, or other medical equipment
Administer only commercially licensed blood or blood products
Keep wounds clean and covered
Ask for proof of a negative EIA test when introducing a horse into a population
Control fly population through proper manure disposal, fly sprays, etc.
There is no available treatment or cure for Equine Infectious Anemia. Since equids infected with EIA virus remain lifelong carriers, the most common recourse is euthanasia or permanent quarantine.
Where Can I Find Information on EIA Outbreaks?
As of March 2020, information on the number and location of EIA affected premises and equines will be shared on the Canadian Animal Health Surveillance System (CAHSS) equine diseases dashboard .
Historical EIA Outbreak maps  of the past can still be accessed via the Canadian Food Inspection Agency website.
SourcesFor more information:
- Canadian Food Inspection Agency 
- Merck Veterinary Manual 
- Equine Disease Communication Center