Immunostimulant Helps Mares with Endometritis Maintain Pregnancy

"Post-breeding endometritis is a major cause of subfertility, affecting approximately 15% of mares," said John Steiner, DVM, Dipl. ACT, of Hagyard Equine Medical Institute. "We know it's a big problem, so we've tried an adjunct treatment to see if this would help."

He and his colleagues recently examined the efficacy of Propionibacterium acnes, sold under the trade name EqStim, and found that it can be useful in treating mares with persistent endometritis so they can be successfully bred. He presented results of the study at the Hagyard Bluegrass Equine Reproduction Symposium 2006, which was held Oct. 18-21 in Lexington, Ky.

P. acnes is a type of slow-growing, nonsporulating, Gram-positive anaerobic bacilli (rod-shaped bacteria), and it's known for causing acne in humans. EqStim is designed to stimulate cell-mediated immunity in horses with bacterial and viral respiratory infections, and veterinarians often use it as an adjunct to antibiotic therapy.

Steiner and his colleagues designed a randomized, double-blind, placebo-controlled clinical trial to evaluate EqStim and its effects on conception, abortion, and live foal rates. Twenty-three practitioners based in either Lexington or Ocala, Fla., participated in the two-year study that examined 112 mares. They administered either a placebo or EqStim intravenously to mares with endometritis (confirmed using uterine cytology indicating inflammation), on Days 1, 3, and 7 of the study, and they were bred within 30 days of the first treatment and were only treated on one cycle. The veterinarian could treat the mare in any other way he/she wished for endometritis.

In the first year of the study (2004), four out of 25(16%) in the treatment group mares aborted, whereas four out of 17 (24%) control group mares aborted (Steiner said dthe 2005 numbers are not available yet). The pregnancy rate of Eq-Stim treated mares was 76%, compared to a 63% rate in the controls. Thus, EqStim increased pregnancy rates by 13%. The veterinarians did not note any adverse reactions in any of the treated mares.

"We know (P. acnes) stimulates a general immune response," said Steiner, "but the mechanism is unclear. It seemed to have an effect, and certainly a statistically significant one."

About the Author

Stephanie L. Church, Editor-in-Chief

Stephanie L. Church, Editor-in-Chief, received a B.A. in Journalism and Equestrian Studies from Averett College in Danville, Virginia. A Pony Club and 4-H graduate, her background is in eventing, and she is schooling her recently retired Thoroughbred racehorse, Happy, toward a career in that discipline. She also enjoys traveling, photography, cycling, and cooking in her free time.

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