Horse Tales: Equine Infectious Anemia

Recently we had occasion to pass by the office of our former veterinarian, long retired, and were reminded of a conversation we had regarding a horse from my childhood.

I’ve always had a passion for horses, and despite being born and raised in the country to parents who were lifelong “city” people and knew nothing about horses or farming, my father decided that I was responsible enough to get my first horse at age 14. The only “hands-on” experiences were learned through 4-H meetings and the kindness of 4-H leaders, who always supplied a horse for trail rides. The end of the summer of 1970 when I was gifted with my first horse was a memorable one. Many happy hours were spent caring for Squire, the patient and tolerant red sorrel with the big white blaze. I would rise before dawn to finish morning horse duties before school, then race back to the barn at the end of the day for as many hours with my horse as possible. That next summer I was proud to ride him in my first horse show at the Sullivan County Fair and bring home the ribbons we had won.

Not long after that summer, I noticed a decline in his health and general well-being. Squire began to lose weight, despite our efforts to increase and supplement his feed, and his lustrous red coat became dull, as were his eyes. His vital signs showed an elevated temperature, heartbeat and respiratory rate, and we called our veterinarian to see what the problem might be. After his examination, Dr. Bartholf was very concerned; although Squire had been up to date on all his vaccinations, what he had was serious – we learned the devastating news that he had a fatal disease for which there was no cure.

Fast-forward about 25 years to 1996; now married and living in a different town across the county from my childhood home, we had purchased two horses and introduced them to our young sons. Happy to learn that Dr. Bartholf was still practicing, we called on him for their routine exams and vaccines. After receiving payment for the farm call, he noticed the name on our check and asked if I was the same Judy who lived in Grahamsville in the early 1970s. Then he said, “You had a red sorrel horse, a gelding with a white blaze…named Squire?” We were quite surprised that he remembered Squire’s name, much less the description of the horse from so many years before. He told us that it was something he had never forgotten – that my horse was one of the first that he encountered with that disease, and how sad it was to tell me. Believing it was likely picked up during exposure to so many other horses at the horse show, as he was stabled alone at our barn, he explained that what Squire had was equine infectious anemia (EIA), and in those days there were no reliable tests available to confirm it. What was most frustrating is that some horses could be carriers of the disease but show no recognizable symptoms and during that epidemic in the early 1970s Dr. Bartholf recalled being called to a farm where one or two horses were sick and others appeared perfectly healthy and having to euthanize all the horses on the property to prevent the spread of the disease. This happened again and again and he stated that those were the darkest days of his career.

Horse Tales: Equine Infectious Anemia

Judy with her first horse Squire. Imagine how difficult it was to be a veterinarian during the EIA outbreak in the early 1970s and having to notify a child that their beloved first horse had contracted a fatal disease for which there was no cure or vaccine. Prior to the development of the Coggins test, entire stables of horses had to be euthanized if even one was found to show symptoms of EIA.

There was a major effort ongoing to come up with an accurate, affordable test to diagnose whether a horse carried the virus and finally Dr. Leroy Coggins and his co-workers at New York State Veterinary College, Cornell University, were successful in adapting the agar gel immunodiffusion (AGID) test to the diagnosis of EIA. Known as the Coggins test, it was recognized in 1973 by the USDA as the official test for the detection of EIA and became the basis for widespread state and federal regulations to assist in eliminating carriers of EIA.

EIA is caused by a virus that affects only members of the family Equidae (horses, ponies, mules, donkeys and zebras) and is found worldwide. The incubation period of the virus is usually about 14 days but can vary from one week up to several months. Symptoms are often non-specific, making it difficult to differentiate from other diseases, and can range in severity from loss of appetite and lethargy to elevated temperature, heart and respiratory rate, severe anemia and sudden death. Clinical signs in the acute stage can include swelling of the limbs, bleeding from the nose, blood in the feces and yellow discoloration of the mucous membranes (jaundice.)

The virus is transmitted by infected blood, primarily by blood-sucking insects such as horseflies and deerflies, but can also be transmitted through the use of contaminated hypodermic needles, surgical instruments, dental floats and bridle bits. Mares can transmit the virus to their foals during pregnancy. Outbreaks frequently develop during late summer and early autumn, which coincides with the peak season for biting insects. The virus triggers an immune response with EIA antibodies, but they are not effective in eliminating the infection.

Some horses survive the acute phase of the disease but will be chronic carriers throughout their lives, often with recurring flare-ups after being exposed to stresses such as other illness or strenuous work. Because there is no cure for the disease, horses that are carriers must be euthanized or permanently isolated and quarantined.

The only protection against EIA is prevention, which is best done by monitoring and testing, and is aided by reducing your horse’s exposure to biting flies by using fly repellants, keeping stables and stalls clean, disposing of manure away from stabling areas and preventing standing water with good drainage. Use only sterile, disposable needles and syringes, one per horse, for all vaccines and medications. Test all horses for EIA every year and participate only in events that require proof of negative Coggins test for every equine entering the event or premises.

Since the Coggins test was developed in the early ‘70s, clinical outbreaks have been greatly reduced, and the rate of infection of EIA in this country has fallen from about 4% to about 0.004%. However, New York State experienced two outbreaks of EIA since 2014 and the number of confirmed EIA cases has slowly increased nationally.

There is still no cure or vaccine for EIA, and horse owners should be aware of and adhere to their state’s requirements.

Buyers should always ask for proof of a current EIA test before purchasing a horse. Horse show managers and boarding stable managers should require proof of a current EIA test prior to entering the premises to protect their competitors and boarders. Horse dealers, auctions and livestock markets all play critical roles in making sure the required tests happen when ownership changes. In addition, the Division of Animal Industry advises all livestock owners to isolate new additions to their herds for three weeks before introduction into the general population on their farms to assist in the prevention of the spread of infectious diseases.

by Judy Van Put

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