The universally recognized test for diagnosis of equine infectious anemia (EIA) — aka “swamp fever” — is the Coggins test. When news of the perfection of this test first broke in 1970, regulatory officials believed it was the tool they needed to eliminate EIA by removing positive horses from the general population. Reality has since tempered those high hopes.
EIA is a viral disease, similar in many ways to AIDS, although it focuses on different blood cell types than the HIV virus. Like HIV, the EIA virus is with the horse for life. Methods of spread are also similar to HIV, requiring either direct blood-to-blood contact or close physical contact that may involve small breaks in the skin or mucus membranes (e.g. breeding). Casual contact between horses will not spread EIA, but reusing needles on horses and biting flies can.
Symptoms Of EIA
Symptoms of EIA include fever, severe anemia, weakness, weight loss, edema of the legs and/or belly and, less commonly, neurological symptoms. Some horses (up to 30% with some strains) get extremely sick when first infected. In this form, the horse will die within two to three weeks. As little as 1 cc of blood from such a horse contains enough virus to infect a million other horses (Source: USDA/APHIS Veterinary Services 1996 Factsheet).
Horses with the chronic form of EIA have bouts of fever, edema, marked anemia and small hemorrhages on the mucus membranes with weight loss and depression. One cc of blood from these horses at times when they have fever (coinciding with large numbers of circulating virus) is sufficient to infect 10,000 horses.
Most horses infected with EIA are asymptomatic carriers. They show no signs of the disease, although the horse probably did have mild fever and depression that were not detected during the first six months after he was infected. As the immune system becomes more adept at rapidly killing the virus, however, you may never know when another wave of virus is being released.
The odds of a biting fly being able to spread EIA to another horse from this group is about one chance in six million bites. To put this in perspective, a horse grazing side by side with an EIA carrier having no symptoms and no fever is about 10 times more likely to get struck by lightning than become infected with the EIA virus.
The problem is that recent studies suggest carriers that appear well may sometimes have significant levels of virus circulating in their blood without any change in their condition — and these horses are highly capable of passing along the virus. Regulations concerning the fate of these horses are highly controversial, but the requirements protect all horses.
Federal And State Laws
Since the first requirements regarding Coggins testing focused on horses moving interstate, many people assume the federal government is behind Coggins requirements and EIA laws. In reality, federal law only regulates the interstate movement of reactor/positive horses and calls for the mandatory branding/tattooing of these horses. Period.
Federal law dictates that any Coggins-positive horse may only be moved across state lines if they are directly enroute to:
• An inspected plant for slaughter,
• Their home farm for quarantine,
• A certified diagnostic or research facility, or
• A sale for the purpose of slaughter where they will move on within five days of arrival. Positive horses at these sales do not have to be quarantined if moving out within 24 hours. Otherwise, they must be held in designated quarantine pens, 200 yards away from other horses.
All other Coggins testing requirements originate with individual states. However, the federal government publishes “Equine Infectious Anemia, Uniform Methods and Rules,” which is a guidebook for the states to use in setting up their EIA control programs. This book suggests no horses be permitted to enter this country or move interstate without a negative Coggins. All states have adopted this rule, although some grant exceptions. Coggins tests for interstate movement must have been drawn within the previous three to 12 months with exact requirements varying by state.
The USDA also suggests a negative Coggins be required for the private sale of horses, public sales and auctions, and all gatherings of horses such as shows, farm exhibits, events, racing, trail rides, and so on. This requirement goes a long way in helping ensure you don’t expose your horse to positive horses when you are away from home. A handful of states also have Coggins-testing requirements for horses traveling on the state’s roads or for breeding stock. Unfortunately, the degree to which the states have taken the USDA’s advice varies widely.
Although some states label their EIA programs as eradication programs, the fact is no disease can be truly eradicated unless all infected animals are identified and destroyed. The Coggins test accurately identifies affected animals, but no law requires all horses be tested. Without this part, any hope of an EIA eradication program falls apart.
Current estimates of the U.S. equine population are between 6.5 and 10 million. Only 1.5 million Coggins tests were performed last year — and it is basically the same horses, from the same specific populations, that get tested each year.
A 1998 report from the National Animal Health Monitoring System (NAHMS), a division of the Animal and Plant Health Inspection Services, showed where samples were originating. Only 55.2% of horse operations in the South had at least one Coggins test drawn in 1997, 36.2% in the Northeast, 18.9% in the West, and 40.3% Central. The larger the operation, the more likely Coggins tests were done. Up to half of the horse operations never even heard of EIA.
With so many horses never tested for EIA, eradication appears impossible. But — even with as many as 8.5 million horses never tested — there is hope. All we have to do is narrow the scope. It’s similar in many ways to controlling crime. You can’t eliminate it entirely, but you can certainly make a big difference in your own neighborhood.
Keys To Success
Protecting your horse from EIA is not difficult theoretically. The biting insects that spread this disease usually don’t travel more than a few hundred yards to feed. They require a warm, moist environment to reproduce. If you keep your horse away from infected horses and protect him from flies, you should be OK.
All barns — public and private — should ensure all horses are tested regularly and each new addition arrives with a current negative Coggins. To be absolutely certain, however, quarantine new additions for about 45 days, then get another Coggins test to confirm, especially if the horse was purchased at a sale or from a large group. It can take that long for a horse with a new infection to show the antibodies.
The real problems arise when you leave home, and this is where we need tougher state regulations.
The USDA Uniform Methods and Rules suggest Coggins testing be required for:
• Any transfer of ownership (i.e. including private sales, loans, leases, gifts, etc.),
• Any collection/assembly of horses for the purpose of shows, competitions, exhibits, etc.,
• All public sales/auctions.
Some states have added Coggins requirements for breeding stock and any horses traveling inside the state. When these measures are adopted, the high-risk horses — those leaving home and coming into contact with many other horses — are much less likely to be exposed.
States with the most rigorous programs, even states with serious biting insect problems like Florida and Louisiana, generally show few reactors and downward trends from year to year in the percentage of samples that turn up positive.
Sounds good so far, but why do we still find well-maintained horses, with law-abiding owners who get Coggins tests as required, turning up positive' Part of the pr oblem is the 8.5 million horses that are never tested. Another factor is the continued existence of reservoirs of EIA (see sidebar). A third, and one we should consider doing something about, is the loopholes in present EIA laws.
Holes In Control Programs
One of the most ubiquitous holes in EIA control programs is with horses intended for slaughter. Even the federal government allows horses intended for slaughter to go through sales facilities and doesn’t require quarantine if they leave the premises within 24 hours.
Horses staying up to five days (the limit) are penned only 200 yards from all other horses. While flies under research conditions may stay inside the 200-yard limit, we’re not so sure about real-life flies. (Sale facilities are supposed to have fly control, but these may amount to no more than fly strips.)
States vary widely in how they deal with these horses. Some allow horses to be sent through regular auctions without a Coggins test, branding or separate quarantine requirements. Furthermore, while many states will say the horse must be intended for “immediate slaughter,” the definition of “immediate” varies from 48 to 72 hours to up to two weeks. Anytime an EIA-positive horse is housed in the same facility as a negative horse, the potential for transmission is there. Horses infected at sales could then carry the infection with them to their new homes.
The state-required radius of quarantine areas for positive horses is most often 200 yards, based on the fact that the biting insects will not go farther than this when there are plenty of horses around to feed upon. It also takes into consideration that not every fly going horse to horse is going to spread the disease. In essence, they are playing the odds.
In reality, horses quarantined on farms or at pasture may be visited by flies that need to travel much farther to get their next meal. In those situations, safety zones of one-quarter to one-half mile in radius around the infected horse are needed to allow for the migratory range of these flies.
Without Coggins testing and required quarantine/control measures, EIA would return with a vengence. However, with 85% of all horses never tested, we aren’t going to get rid of it.
We urge you to support stringent Coggins testing laws and ask event/show/trail managers to check Coggins testing even if not dictated by law. Assume personal responsibility for not exposing your horse to any untested horses. Avoid barns that do not require negative Coggins tests before accepting horses. Boycott shows, sales, etc. without requirements.
Urge your state horse council to work hard to end loopholes in laws that allow positive horses to go through sales with negative ones and ask for more stringent quarantine requirements for EIA-positive horses at sales.
The sad fact is that it is the law-abiding owner who has his/her horse regularly Coggins tested who stands to pay the highest price if loopholes result in an EIA outbreak in the general population. Let lawmakers know the stakes are too high.
Also With This Article
Click here to view "No Cure, No Vaccine."
Click here to view "High Price Of Not Obeying The Law."
Click here to view "Do Strict Coggins Enforcements Help'"
Click here to view "Coggins Testing Can Work To End EIA."
Click here to view "Reservoirs of the EIA Virus."
Click here to view "Could Your Horse Be Exposed'"
Click here to view "If Your Horse Tests Positive."
Click here to view "State Coggins Test Summary."