Correcting the defects in uterine defense, neutralizing virulent bacteria, and controlling post-breeding inflammation are the goals of successful therapy. This is accomplished by surgically correcting anatomical defects, improving physical drainage after insemination, reducing the length or modulating the inflammatory response to insemination and inhibiting bacterial growth. Post-breeding inflammation is most commonly treated by improving physical clearance of uterine fluid with uterine irrigation followed immediately by administration of either oxytocin (10-25 IU i.v. or i.m.) or cloprostenol (250 μg i.m.). In some cases, the uterus is infused with antibiotics post mating. Bacterial or fungal endometritis are routinely treated for 3 to 5 days during estrus with either intra-uterine or systemic antibiotics in combination with uterine irrigation. Emphasis here will be on the use of mucolytics, chelating agents and administration of steroids for modulating the inflammatory response.

Mucolytics

Not all infections respond to uterine irrigation and antibiotic treatment. Treatment failure may be due to continual contamination of the uterus because of anatomical abnormalities in the caudal tract, degradation of antibiotic in uterine exudates, or biofilm production by the micro-organism. Previous work indicates that mucus secretion increases during experimental uterine inflammation, and in mares with delayed uterine clearance and bacterial endometritis. Mares with chronic endometritis have an increase in the thickness of the mucus ribbon overlying the endometrium, increased staining intensity of both intracellular and extracellular mucus, and epithelial cell loss. Excessive mucus or exudate can interfere with antibiotic penetration, can render aminoglycosides chemically inert or may interfere with sperm transport to the oviduct. Treatment with a mucolytic agent may help clear mucus and increase effectiveness of intra-uterine antibiotics. Solvents and mucolytic agents have been added to uterine irrigation fluids in an attempt to clear exudate, mucus or biofilm. Agents used include DMSO, kerosene and N-acetylcysteine. Each compound appears to have some beneficial effects. Barren mares (n = 16) infused with a 30% solution of DMSO after breeding tended to have higher pregnancy rates than mares infused with saline. Intrauterine DMSO therapy also resulted in a significant improvement in endometrial biopsy classification in 18 of 27 mares; whereas only 2 of 18 barren mares improved following intrauterine saline treatment. In contrast, intrauterine infusion of 50 ml of commercially available kerosene in 26 mares with varying degrees of endometrial pathology induced diffuse moderate to severe endometritis, severe diffuse edema and production of a serum-like exudates. Half of the mares exhibited mild to severe necrosis of luminal epithelium. Mares were subsequently bred on the next cycle and surprisingly, 50% of the mares with Category II or III biopsy scores carried foals until term. Although kerosene was associated with significant inflammatory changes, pregnancy may have been established because mucus and exudate were removed via destruction and necrosis of uterine epithelium.