Equine Infectious Anemia Explained

Can you please give me any info you have on equine infetious anemia? I have an older horse and he is sick. The vet said he is very anemic, but not what to do please help. He is more family then pet. Thank-you Pam

Story originally posted by: Dr. Michael Lowder, DVM, MSUniv. of GA School of Veterinary Medicine



There are many causes of anemia as I am sure your vet told you. Depending upon what type of anemia your horse has your vet should be able to recommend a course of treatment to you. In regards to equine infectious anemia (EIA) I will repeat an earlier answer.

Dr. Leroy Coggins developed the coggins test in the early 1970s. The purpose of the test is to test for the disease “equine infectious anemia” also called “swamp fever”. Most states require a coggins test on any horse (mature horses and foals over six months of age) that is transported within or through their state. The test must be within six to twelve months and varies with state. You can call your local vet to find out what the requirements are for your state or contact your state veterinary’s office or look on the web HERE. Equine infectious anemia (EIA) is a slow acting lentivirus (a member of the retrovirus family) that use the RNA of a cell to produce their DNA with is incorporated into the genetic makeup of the infected cell.

The virus is highly infectious and is transmitted by biting insects (mosquitoes, horse flies, etc.) and has the potential to be transmitted by blood contaminated instruments, transplacentally or colostrum. The coggins test is a serological test (agar-gel immunodiffusion test) that test for antibodies against the EIA virus in the horse’s blood. An acute, chronic and inapparent form characterizes the disease. The acute form is seen between 7 to 30 days after the horse is infected (the horse may test negative for up to 45 days after being infected) in which the horse develops an elevated temperature (up to 105(F) that usually last less than 24 hours.

The horse becomes lethargic, anorexic and most owners do not notice any significant change in their horse’s behavior. The chronic form have recurrent viremia and fever, weight loss, dependent edema, anemia, lethargy and depression. The chronic form is the one most commonly associated with the name “swamp fever” which comes from horses that are stabled or pastured near water. In the inapparent form, the horse recovers from the acute form and never develops the chronic form and therefore is a potential source of infection for other horses.

There are no vaccines for the disease and testing is the only control. The fate of positive horses depends upon the individual state laws, which usually involve lifelong quarantine, euthanasia or donation to a research facility.

Dr. Lowder