Equine Infectious Anemia (EIA): What You Need To Know

The Coggins test. Many of you reading this may know why horses need routine Coggins testing, however, some of you may just see it as a pesky nuisance required to cross the border. At Energy Equine, Coggins tests are on the rise, simply because more and more equine facilities are requesting negative Coggins for equine athletes that are on site. Due to this trend we felt we should shine some light on the Coggins test, and specifically what we are testing for – Equine Infectious Anemia (EIA).

What is EIA?

Equine Infectious Anemia (EIA) is a virus that is sometimes referred to as “Swamp Fever.” This is a misnomer, it was labelled Swamp Fever because when first diagnosed in the 1880’s it was believed to only occur in wet and humid regions of the southern United States. However, EIA is found worldwide, including Canada where its presence is mostly detected in the western provinces. EIA is spread through mechanical transmission, which typically is the result of a blood-feeding insect such as a mosquito or horsefly feeding on an infected horse and having it’s feeding cycle interrupted. Perhaps the horse flicked its tail at the insect, or jumped from the bite. When disturbed, the fly will then jump to an uninfected horse and can spread the virus from there. The virus does not live long on the mouth of the insect and flies don’t travel long distances, so EIA is more likely to be spread to horses that live together.

EIA can also be transmitted via medical equipment such as needles, syringes, IV tubing or other equipment contaminated with blood or through transfusion of blood or blood products from an infected horse. Although we find that most horse owners recognize this risk, it is always something to keep in mind. The sharing of needles, syringes or other blood-contaminated equipment from horse to horse is never a good idea.

The incubation of the virus is 15 to 45 days. Signs and symptoms include fever, depression, low platelet count, anemia, red or purple spots on the mucous membranes, edema, muscle weakness and muscle atrophy. Other visible signs can include jaundice and swelling in the legs, under the chest and other areas. At this early acute stage of the virus diagnosis can be difficult, as it sometimes takes anywhere from a week to a month for antibodies to be detected, which renders the diagnostic tests ineffective.

Horses can die within a few weeks of exposure to EIA but many survive. Horses that have been infected with EIA are lifelong carriers, however horses that are showing clinical signs of the disease are more of a threat to healthy populations because of higher levels of the virus concentrating and circulating in their blood. Horses that survive the initial clinical phases of the disease usually become carriers within a year, but they will remain a reservoir for the disease for the remainder of their lifetime. Horses can also be carriers and never show symptoms of the virus.

Testing for EIA

This is where our friend the Coggins test comes in to play. EIA is diagnosed by testing antibody levels in the blood – essentially the antibodies are what is fighting the EIA in the horse’s body. The Coggins test was invented by Dr. Leroy Coggins of Cornell State University in 1970, the development of this test led to EIA control programs across North America. In 1971, EIA was designated a reportable disease under the Canadian Health of Animals Act.

Under the current EIA control program all suspected cases of EIA must be reported to the Canadian Food Inspection Agency (CFIA) which has legislated control and reporting measures for the disease. If a horse tests positive for EIA, the CFIA will respond by implementing control measures. The CFIA will generally order a quarantine on the farm or facility where EIA-infected horses are suspected. All horses that have been in contact with the suspected horse within the previous 30 days are tested. If the tests come back positive, the horses will be retested. Anything that re-tests positive and shows clinical signs are ordered destroyed. Horses that are confirmed to be infected, whether they show clinical signs or not, are ordered to be euthanized or put in a permanent quarantine in a fly-proof facility and are permanently identified with a brand or tattoo.

Prevention

There is no vaccine available for EIA, and as detailed above, this tragic disease almost always ends in euthanasia due to the poor quality of life that a life-long quarantine sentence offers a horse. Methods of prevention include insect control to reduce the possibility of transmission and ensuring that needles and other medical equipment contaminated with blood are never shared between horses.

Insect control includes:
– Use insect repellents frequently and re-apply after rain
– Keep horses in at night when possible and apply insect repellant
– Eliminate or minimize standing water
– Stock tanks or ponds with mosquito-feeding fish
– Eliminate brush piles, gutters, old tires and litter
– Remove all equipment in which standing water can collect
– Practice fly control by managing manure piles and routinely cleaning pastures

Biosecurity protocols should be in place at boarding facilities. Consider all horses EIA carriers until they provide a negative Coggins, or test negative. Isolate all new horses for atleast 45 days, checking their temperature daily to check for fever and keeping an eye out for other signs of illness.

Routine EIA testing should be performed to determine the status of horses in an area and thus prevent transmission of the virus to horses nearby. As many show facilities are now requesting negative Coggins, we are seeing a rise in Coggins testing that isn’t necessarily for out-of-country travel. The Alberta Veterinary Medical Association (ABVMA) suggests that horses should be tested annually but horses at a greater risk (an example being equine athletes that travel frequently) should be tested every 4-6 months. Coggins tests for out-of-country travel are sometimes only valid for 6 months dependent on the states you are travelling through. The test for Coggins is quite simple and pain-free. An Energy Equine veterinarian can either pull the blood to be sent to the laboratory on site at the clinic, or at your farm or boarding facility.

More and more we are seeing boarding facilities host herd health wellness days. This is an excellent way to have a veterinarian come out, perform fecal exams for deworming protocols, administer routine and requested vaccinations, and pull blood for Coggins exams. These days provide peace of mind and set owners up for success long before show season starts.

Although a worrisome disease, owners should not panic. If you are practicing insect control, biosecurity measures, herd health and wellness protocols, you are going above and beyond to protect your horses from EIA. The disease is not fast-moving and Canadian regulations are in place to diligently watch for cases of the disease. Like all things in horse ownership, owners should be aware of the signs and symptoms, and what they can do to protect their horses against EIA.

Sources
https://aaep.org/sites/default/files/Documents/Outside%20Linked%20Documents/DiseaseFactsheet_EIA_0.pdf