Coggins Test

While on the phone the other night with a good friend talking about horses we got on the subject of the Coggins test.  I asked her what is the Coggins test and why do we do it?  I don’t recall ever having this test done way back when I had my horses. We talked a bit more about it and then she suggested it to be an article here at Kritter Korner. So with that in mind I started searching for information.

In the 1970’s a veterinary virologist, Dr. Leroy Coggins of Cornell University developed the Coggins test also know as the agar gel immunodiffusion (AGID) test. This serum test is reliable and detects the presence of Equine Infectious Anemia (EIA) specific antibodies in the blood. EIA is also known as Swamp Fever, because the disease has been associated with wet, warm regions, note EIA is NOT limited by geography. A negative reading means no detectable antibodies at that time, positive indicates the horse is infected and a carrier of the virus. The Coggins test was made the official test for EIA by the United States Department of Agriculture in 1973.  You ask why this test is so important. Well it’s because Equine Infectious Anemia (EIA) is a serious, contagious, viral disease with no cure and no horse has ever recovers from it. EIA affects the horse’s immune system and threatens horses worldwide. EIA has been around for centuries, reported around the globe. At risk are horses, ponies, mules, donkeys and zebras, and once they are infected they are infected for life.  EIA is a slow-acting virus in the family of the lenti-retrovirus group related to the viruses that cause bovine leukemia, feline leukemia and AIDS (acquired immune deficiency syndrome) in humans. EIA was first identified back in 1843 in France, in 1881 reported in Canada and a single case in New Zealand and also in Wisconsin in 1888. Two major outbreaks occurred in 1901, Wyoming suffered an epidemic and in 1947 New Hampshire’s Rockingham Park was the site of another outbreak resulting in 77 horses dying or having to be euthanized because of EIA.  The EIA virus circulated throughout the body, reproducing in the blood cells. The immune system via antibodies attacks and destroys the infected red blood cells. This reduces blood count causing anemia, vital organs like the liver can become damaged by the associated inflammation. Other organs this virus attacks are the spleen, kidneys, and lymph nodes. Because the immune system is impaired the horse may also become susceptible to secondary infections like bronchopneumonia. Horses infected by EIA usually die from the virus or from secondary infections. EIA is difficult to diagnose because symptoms vary and it can mimic other diseases plus some horses may show no obvious signs at all. There are three forms of EIA acute, Chronic, and in apparent.

1.    Acute, during which the virus is active, multiplying and harming the immune system and other organ systems.

2.    Chronic, during which the animal may vacillate between remission and disease states. The horse may be thin or in poor body condition, and may suffer recurring bouts of clinical signs, as seen in the acute phase.

3.    In apparent, during which the horse carries the virus but shows no apparent symptoms. Stress or disease may bring on an acute episode[a].

Acute EIA
While acute responses to EIA infection are rare in natural situations where blood-feeding insects transmit low doses of the virus, it is useful to describe this scenario.
Unfortunately, the clinical signs of acute EIA are rather nonspecific. The predominant symptom is fever, which may appear rapidly but last less than 24 hours. Even vigilant horse owners and veterinarians might miss or incorrectly diagnose the fever because it can be short-lived and because fever is also a response to many other equine diseases (like influenza, also known as flu, and equine encephalitis, also known as sleeping sickness). In some cases death can occur within two to three weeks.Possibly the horse will survive this first acute attack and appear to recover… maybe even without having been diagnosed as ill. If the horse escapes detection at this stage of the infection, he may continue to move freely among other horses; this is risky.
The first indication that the horse was exposed to and infected with EIAV may well be a positive test result on a routine annual test.

Chronic EIA
The horse that survives the acute phase may have recurring episodes of the disease. These bouts are thought to be caused by new mutant EIAV strains generated in the infected horse. Signs can include very high fever (105 – 108 degrees), tiny spots of hemorrhage on the mucous membranes, depression, weight loss, edema of the lower body, irregular heartbeat, and anemia. It is during the acute phase or recurring episodes that the horse is most infectious.

In apparent Carriers
By far the majority of horses who test positive for EIA are carriers that appear healthy. They may have low or high amounts of the virus in their blood (and it is not easy to determine which is the case). In general, the chances of transmission from an in apparent carrier are lower than from a horse with clinical signs of EIA.In apparent carrier horses, when stressed, can begin to exhibit clinical signs. Stressors may include the environment (severe weather or drought), hard work (overexertion over time), or by other disease (encephalitis, etc.). Prediction of which in apparent carrier is likely to exhibit clinical signs is difficult. When exhibiting clinical signs, in apparent carriers pose an increased risk to other horses.[b]

Now you wonder how my horse gets EIA. Well it is transmitted by blood via blood sucking insects like the horse fly, deer fly, stable flies and sometimes human using hypodermic needles. Horse flies are considered the highest risk carrier due to their large size. According to the Penn State College of Agricultural Science department, research has shown that flies are unlikely to travel more than 200 yards when feeding. As a result, when horses are quarantined for EIA, the USDA mandates the minimum distance is 200 yards for keeping infected individuals apart from healthy animals.[c] The blood sucking insects bites an infected animal and carries the residual blood which contains the virus on its mouthparts as it travels about from one host to the nest spreading the virus. EIA can also be spread by humans in the same why by using a single needle when giving injections on multiple horses. It can also pass in utero from mare to foal.The risk of transmitting the disease is greatest when an infected horse is ill, as the blood levels of the disease are high enough to infect the blood-feeding insects.[d]

EIA is not transferable to humans because it is not directly contagious from one horse to another, it can only be spread through contaminated blood.There are several factors that can put your horse at risk such as exposure events like horses shows and sales where health care regulations are not enforced and a negative Coggins certificate is not required. Damp swampy area pastures where insects are abundant, and the close proximity to regions where EIA outbreaks have occurred. There is no effective treatment for EIA and no vaccine to prevent it, so prevention is the best way to protect your horse. Here are some things you can do:Use disposable syringes and needles when giving medications and vaccines. Sterilize dental tools and other instruments before using them on another horseAll stable areas should be kept dry, clean and waste free. Remove manure and provide adequate drainage to discourage breeding sites for pests in your pastures.Have your veterinarian perform a Coggins test on your horse annually.Before bringing a new horse onto your property make sure it has been tested beforehand and has a negative Coggins.Only board your horse where a negative Coggins test is required of all horses at the facility.Only participate in shows and events where negative Coggins is required.

FEDERAL & STATE REGULATIONS
The USDA requires that horses being imported from foreign countries test negative to the Coggins test, along with other tests. Within the U.S., each state drafts its own specific requirements regarding EIA and the movement of horses interstate, intrastate, and in change of ownership. Learn what is required in your state and states you will be visiting. Be aware that laboratory results take time, and plan to have your horse tested in time to get results before you must transport your horse. By law, EIA is a reportable disease. All positive cases must be filed with the state veterinarians and the federal Animal and Plant Health Inspection Service (APHIS) office.[e]

All horses that test positive for EIA are also required by law to be permanently identified by either branding, tattooing and to be quarantined.Stopping the spread of EIA is everyone’s responsibility. If you suspect a horse has EIA, call your Veterinarian or state animal health agency immediately. They can assess the animal and initiate the required tests. Owner compliance with Coggins testing and the destruction of most known reactors has aided in a marked decline in EIA cases in the last 20 years. Today fewer than 1 percent of the 1 million horses tested annually are found to be carriers. But with an estimated 6.6 million horses in the

U.S., more widespread screening is needed. Even backyard horses that never leave the property will benefit.[f] By having your horse tested, you will be doing yourself and the entire equine industry a favor. The cost is minimal; the price well worth the peace of mind.

Sources:http://www.eqgroup.com/Library/coggins.
htmhttp://www.ruralheritage.com/vet_clinic/coggins.
htmhttp://www.horses-and-horse-information.com/articles/0696eia.shtm
lhttp://www.wiwfarm.com/coggins.htm 

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[a] http://www.dclahdvm.com/articles/anemia.htm

[b] http://www.eclectic-horseman.com/newsletter/EIA.php

[c] http://www.oddsonracing.com/docs/EIACogginsTest.cfm            

[d] http://en.wikipedia.org/wiki/Equine_infectious_anemia

[e] http://www.dclahdvm.com/articles/anemia.htm[f] http://www.dclahdvm.com/articles/anemia.htm