Equine Ehrlichiosis
Thomas B. Massie, Jr., DVM

This is a disease that has been seen with increasing frequency in our area over the past few years. It affects horses of all ages and the symptoms are usually noted suddenly. Unlike many diseases, this condition causes less severe symptoms in younger horses (less than three years).

The disease is caused by Ehrlichia equi and is transmitted by ticks of the Ixodes family (deer ticks). This condition is related to several other more known diseases such as Lyme Disease and Rocky Mountain Spotted fever. The clinical symptoms are seen most frequently in the winter, spring and fall. The most commonly noted symptoms are depression, anorexia, weakness, limb edema, fever (early in the disease), and immunosupression. The bacteria tends to be engulfed by white blood cells and causes accelerated destruction of these infection fighting cells. After initial infection, the horses will be normal for 10-20 days prior to developing clinical signs.

After clinical signs develop the horse will deteriorate rapidly and often will show mild signs of colic and become jaundiced over the next 3-4 days. Most horses will survive after 10-14 days of severe illness, but some will develop subclinical infection. Diagnosis is made through a combination of clinical signs, blood analysis, environmental conditions, and response to treatment. With early and aggressive treatment, most horses become more normal within 24-36 hours and complete recovery is usually noticed within seven days. Unlike many diseases, this disease responds well to intraveneous Oxytetracycline given for seven days. Some will require more aggressive therapy including IV fluids, diuretics, wrapping, etc.

At this time, prevention is solely by reducing exposure to ticks as no vaccine is currently available.

This article comes from Rose Hill Veterinary Practice website, www.rosehillvet.com