The Horse:Your Guide To Equine Health Care provides monthly equine health care information to horse owners, breeders, veterinarians, barn/farm managers, trainer/riding instructors, and others involved in the hands-on care of the horse.
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35 February 2016 THE HORSE TheHorse.com Persistent mating-induced endome- tritis One of the most common causes of reduced fertility in mares, persistent mating-induced endometritis is chronic inflammation of the uterine wall lining after breeding or artificial insemination. McCue said mares, especially older ones, are sometimes unable to clear sperm, fluid, and inflammatory de- bris from the uterus after breeding. "Inadequate or insufficient muscular contractions of the uterus and/or a cervix that failed to relax sufficiently are the most common causes for the retained fluid and persistent inflammation," he said. Should an embryo enter the uterus that still has inflammatory fluid present, it would be unable to survive, McCue said. Further, he added, this persistent inflammatory fluid buildup can cause the endometrium to release the hormone prostaglandin, which adversely affects development and function of the corpus luteum, a structure formed after the fol- licle ovulates, and subsequently decreases progesterone (the so-called pregnancy hor- mone) production. This can result in low progesterone levels and/or s hort-cycling. McCue said treatment is focused on reducing the severity and duration of the mare's inflammatory response and clear- ing her uterus of detrimental substances. He recommended breeding at-risk mares only once during an estrous cycle and timing the breeding to take place imme- diately prior to ovulation. For additional measures, veterinarians can lavage the mare's uterus with sterile saline or sterile lactated Ringer's solution four to six hours after breeding and/or administer oxytocin, which will help stimulate uterine contrac- tions to remove the fluid. Bacterial endometritis Uterine inflam- mation in conjunction with a bacterial infection is another common cause of reduced fertility. "A majority of young mares eliminate bacterial contamination of the uterus following mating, parturition (foaling), intrauterine manipulations, and other events," McCue said. "In contrast, some older multiparous mares (those that have had many foals) may be unable to sponta- neously eliminate pathogenic organisms from their uteri and are considered to be susceptible to bacterial infection." He said risk factors for developing bacterial endometritis include: ■ Contamination during breeding; ■ Urine accumulation in the vagina and/ or uterus; ■ Trauma from breeding or giving birth; ■ Failure of natural defense mechanisms, such as white blood cell function, local antibody production, etc.; and ■ Poor perineal conformation. "The general principles of a treat- ment regimen are to remove the source of infection, aid in physical clearance of the uterus, eliminate pathogenic organ- isms by local infusion with antimicrobial agents, and reduce future contamination by enhanced reproductive management," McCue said. He noted that if poor perineal confor- mation or decreased vulval muscle tone are a concern, the mare might benefit from a Caslick's procedure (suturing closed the upper part of the vulva) to prevent contaminants from entering the reproductive tract. Fungal endometritis A third cause of endometritis—and one that is more difficult to diagnose and eliminate—is fungus in the uterus. "Fungal infections of the uterus most commonly occur in older mares with reduced uterine defense mechanisms receiving prolonged antibi- otic therapy," McCue said. He described a variety of clinical presentations for fungal endometritis, ranging from no clinical signs to severe purulent (producing pus) endometritis with chronic infertility. Chronic fungal or bacterial infections can cause permanent damage to the endometrium if not diagnosed accurately and treated properly. The chronic inflam- mation and scar tissue development can lead to markedly reduced fertility. McCue said fungal endometritis treat- ment focuses on correcting predisposing factors (including perineal conformation- al deficits), removing debris via uterine lavage, and using local and systemic antifungal agents. What if treatment fails? Despite best efforts, treatment doesn't always work. In these cases, McCue recommended veterinarians: ■ Take a closer look at the case, re- examining the original diagnostics and considering whether there could be multiple issues at play; ■ Consider alternative or complementary therapeutic techniques; and ■ Employ advanced reproduction tech- niques, such as embryo transfer or intracytoplasmic sperm injection. Finally, he encouraged veterinarians to consider consulting a reproductive spe- cialist, referring the patient for a second opinion, or performing additional diag- nostic procedures if the initial treatments are ineffective. h Endometritis, defned as an infammation of the uterine wall lining, is one of the most common causes of reduced fertility in mares. DR. ROBIN PETERSON Fungal infections … most commonly occur in older mares with reduced uterine defense mechanisms receiving prolonged antibiotic therapy." DR. PATRICK MCCUE Cervix Ovaries Fluid and infammation Uterine horns