Fact Sheet

Introduction to Equine Infectious Anemia (EIA / Swamp Fever)

Fact sheet prepared by Doug & Karen Brown based on the information that we have been able to gather from all sources to this point in time. Most of the information included comes directly from reports published by active EIA researchers. Many U.S. universities had projects underway before the Test and Slaughter or quarantine policies limited the researcher's abilities to answer the complex questions surrounding the disease. Information indicates that the disease was officially recognized by the veterinary community as early as 1843 in France.

The virus responsible for the infection is designated as a lentivirus of the family of retroviruses which include Human Immunodiffiency Virus HIV (humans), SIV (monkeys), FIV (cats) also including similar ones affecting other domectic as well as wild animals. Viruses of this family are able to incorporate their RNA into the DNA of host cells thereby evading the immune system of the animal while they remain dormant. Like the Equine Herpes Virus which causes the infections known as EHV and EHVM, it also has the ability to mutate so as to produce a new identity which might not be recognized by the antibodies which were produced to counteract the initial infection.

EIA is a reportable disease in Canada affecting horses, mules and donkeys.

EIA is rare in the horse population of Canada. Based on historical data testing approximately 65,000 horses per year with an EIA incidence rate varying from 0.05% to 3.2.%.

The simplest way to describe this infection is to separate it into the following forms:

Acute: A rapid advancing condition characterized by fever, edema, anemia, petechial hemorrhage, weight loss, depression, loss of muscle function and death. If the horse’s immune system cannot control the virus attack, this form ends in death. (Even the acute case will not transmit explosively, but requires particular circumstances). In the acute form of the disease, the animal has a high enough viral titer in the blood to transmit to other horses if a method of transmission is available. These are potentially dangerous animals.

Chronic: An initial attack followed by periodic recurrences of disease, indicated by fever and varying degrees of the symptoms described above, sometimes several times per year, sometimes years apart. The disease gradually takes its toll on the animal, creating an unthrifty appearance etc., historically known as a “swamper”.

Subclinical: Sometimes called latent, asymptomatic or inapparent carriers. Most common form. (85% to 95% of all AGID (Coggins test) positive horses fall into this category). Appearing normal physically, athletically and reproductively with no apparent effects of the virus. Although these horses have become infected with the EIA virus and carry antibodies in their bloodstream, they are for all intents and purposes free of disease. The viral titer in the subclinical animal has shown to be below a transmissible level, under normal field conditions.

Occult: This in the animal that consistently tests negative on a Coggins test, but has been shown to be capable of spreading the disease. (Some people like to deny the existence of this form or at least downplay the significance of it but occurs repeatedly in research reports and should be considered seriously in any program which relies heavily on the use of the Coggins or ELISA test.)

The Coggins Test

Coggins Test: An agar gel immunodiffusion test modified and patented by Dr. Leroy Coggins in 1971. Considered for many years to be the standard test for EIA worldwide. Promoted as being approximately 95% accurate, it is subject to human interpretation and does produce varying results between labs and lab technicians. In recent years it has been shown to be less sensitive than the enzyme based tests. The Coggins test only determines whether or not there were EIA antibodies present in a horse’s system during that moment in time in which the sample of blood was drawn. Many people have been lured into the false belief that a negative test somehow offers protection for their horse, or for other horses they may come in contact with, for a period of several months or more when in fact it only indicates the state of their horse’s immune system at the moment the sample was taken.

A positive Coggins test is many times more deadly than EIA itself. (Estimates suggest that when left in a natural state, the disease would kill 1 out of every 20,000 horses but "test and destroy" has killed as many as 600 out of every 20,000 subjected to it.)

Conclusions

Based on all the information we have received we feel there are too many unanswered questions to destroy subclinical horses. Because the disease has always been self-limiting is there perhaps a genetic factor that helps control the virus? See: Points of Interest. In a fax we received, Dr S. McConnell states "You are correct in your assumption that by eliminating the EIA virus from the environment that with time all horses will become much more susceptible."

"Fear of the unknown is the worst fear of all and the most difficult to dispel".

Given the fear, misinformation, lack of knowledge, limited statistics and current policy; human nature is to panic.

Alternatives

Common consensus is that eradication of EIA in this country by means of the test and slaughter method is impossible for a number of reasons.

As open minded logical horsepeople why do we not use a more constructive approach?

Wouldn't it be nice if some of the money getting spent to administer these programs could be used to save the life of the asymptomatic horse (which is innocent), through investigation of procedures like those used by Dr. S. McConnell (at Texas A&M) to determine which horses present a danger and which do not? Perhaps some money could be used simply to educate horse owners, and regulators as well, to better understand the nature of the infection. Why do we not seriously look into the information that other countries are looking at? What about a vaccine? China claims to have a vaccine as well as a test to differentiate which horses have been vaccinated and which have not. It is easy enough for people in positions of authority to disclaim information, but so far it has been impossible for these same people to provide researched, documented facts to prove their position. Show us documented proof that a subclinical (asymptomatic) horse has ever been responsible for transmission of the disease under normal field conditions!

As responsible horse owners we feel that it is up to every horse owner to push for further investigation and research, and stand totally against the destruction of animals based solely on the presence of antibodies in that animal's bloodstream.

Comments

WE BELIEVE IN A CONTROL PROGRAM, but not one that kills apparently healthy horses indiscriminately.

In order to change this barbaric approach to the handling of the EIA situation in Canada, or the world for that matter, we suggest:
-read every piece of research information you can get your hands on,
-make your opinion known to the people in the positions to make decisions, and ask for a list of documented research that they have based these decisions on; after all it is their responsibility to gather and consider all the information so that truly informed decisions can be reached. People in positions of authority must be sadly indifferent if they do not avail themselves of all the facts before issuing a death warrant for an innocent asymtomatic horse.
-boycott shows requiring a negative test until the policies are changed,
-make other horsepeople including show management aware that there could be alternatives, but only if we are prepared to insist.
The time for complacency is over.

Perhaps if the policies were changed to remove the death sentence for the asymptomatic horse, it would be easier to educate horsepeople on the signs of the acute and subacute horse, and the importance of checking out all sick horses including the "poor doers". Perhaps if the stigma were removed from the AGID Positive asymptomatic horse, you would see more of the horse population tested voluntarily and thereby achieve better overall control of the disease.