The Coggins Test... What is this pesky piece of paper anyway?

It’s that time of year again! Spring is around the corner and we’re all getting our horses out and getting ready to ride again. If you're planning on going anywhere with your horse you’ll need to make sure you have an up to date “Coggins”. So what is that pesky piece of paper anyway? Coggins is a blood test for horses or other equines, named after Dr. Leroy Coggins who developed this test in 1970. This test screens for the Equine Infectious Anemia Virus (EIAV) also referred to as “Swamp Fever”….If you’ve never heard of it by this name, it’s likely because the strict testing requirements have been implemented to control this disease.

As it says in the name, Equine Infectious Anemia is a disease that causes anemia (or a low red blood cell level) in horses. The virus alters the makeup of a horse’s red blood cells causing the horse’s own immune system to destroy the cells. This very contagious virus is transmitted to other horses through biting insects (mostly larger biting flies) or equipment such as needles or surgical instruments, contaminated with blood from an infected horse. Interestingly enough, the EIA virus is a retrovirus, the same genus and family as HIV in humans.

Horses infected with the virus can fall into three categories. Acute infections, chronic infections and inapparent carriers. Acute and chronic infected horses will show clinical signs. Acutely infected horses are horses that have been infected within 30-40 days and will generally have a fever, be lethargic, and have no appetite but will not yet have a positive coggins test which may not lead to an immediate diagnosis of EIA. Chronic infected horses will have a positive coggins test. They will also have recurrent fever, weight loss, ventral edema and of course anemia. The third group of horses, inapparent carriers, are the horses that are of more concern and make up the largest group of infected horses. These horses show no outward/clinical signs of being infected yet can be a source of transmission to other horses. Since they are infected, these horses will also test positive on a coggins test.

So, if most horses don’t have clinical signs, does it really matter? There is no cure or treatment for EIAV. Once a horse develops clinical symptoms, supportive care can be given however, eventually the horse will succumb to the disease and die. In 1972, the Coggins test started to become mandated by states. As part of the mandate, horses who tested positive are required to be reported to state and federal authorities and either have to be euthanized or branded and quarantined for life, at least 200 yards from other horses. In 1972, almost 4% of the horse population in the United States was infected. The extreme mandates were effective. By 2005, less than 0.01% of the horse population tested positive. In 2014, the estimated horse population in the United States was about 10.3 million, this would mean, if we still had a 4% infection rate there would be almost 412,000 infected horses. However, today, with strict regulation, the disease affects less than 1,000 horses in the United States. While it may seem like a pain to pay for a coggins test every year, it’s a small price to pay for the comfort of knowing your horse is safe and healthy.

In the state of Wisconsin, a coggins test is required for all horses being imported, entering exhibitions or competitive events, participating in an organized trail ride or training seminar, being moved interstate, changing ownership, or entering auctions or sale markets. A coggins test result is valid for 12 months from the date the blood was sampled.

For more resources to learn about EIA:

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