Endometritis in Production Animals

The pathogenesis of endometritis in cows is not fully understood, but it is becoming increasingly clear that postpartum uterine diseases, particularly in high-producing dairy cows, are mediated by an impaired immune response, probably related to negative energy balance. In cows, the dominant organism linked to endometritis is Trueperella pyogenes. Cows developing endometritis may delay differentiation between the microbiome of the vagina and the uterus. Opportunistic pathogens from the normal vaginal flora or the environment may invade the uterus from time to time. A cow with adequate immunologic response can eliminate transient infections, but cows with inadequate immunologic status may develop chronic endometritis.

Clinical endometritis in cows is characterized by the presence of purulent (>50% pus) or mucopurulent discharge (approximately 50% pus and 50% mucus) in the vagina after 21 days after parturition without systemic signs. The name clinical endometritis has been questioned. An alternative name suggested is purulent vaginal discharge, because, in some cases, the pus identified in the vagina is from the cervix or vagina, not the uterus.

Subclinical endometritis in cows is characterized by endometrial inflammation of the uterus determined by the presence of a threshold of PMNs on cytologic examination without the presence of purulent material in the vagina.

Clinical endometritis in cows can be diagnosed by use of a vaginal discharge collection device or vaginoscopy, or based on purulent discharge in the perineal area. The presence of more than 50% on the sample collected after 21 days after parturition can be used as a criterion to diagnose clinical endometritis.

Subclinical endometritis in cows is diagnosed through the collection of a uterine lumen sample for cytologic evaluation using either cytobrush or cytotape techniques or uterine lavage. A threshold to characterize subclinical endometritis has been described: >18% PMNs in samples collected at 20–33 days after parturition or >10% PMNs in samples collected at 34–47 days after parturition.

Cephapirin benzathine (500 mg, intrauterine, once; second treatment may be required in 7–14 days if clinical signs persist) has been shown to improve reproductive performance in cows with endometritis; however, this product not available in the US. All other systemic and intrauterine treatments should be discouraged. The body of evidence from the scientific literature shows that the administration of PGF2-alpha is not effective for the treatment of clinical endometritis or subclinical endometritis.

The control of endometritis includes providing adequate comfort, sanitary, and nutritional management during the transition period to minimize the risk of calving and postpartum health disorders associated with predisposing factors. Some nutraceuticals, such as chromium propionate, have been associated with reduced incidence of endometritis.

In mares, the most common etiologic agent of endometritis is Streptococcus zooepidemicus. Several other organisms may be involved, including Escherichia coli, Pseudomonas aeruginosa, and Klebsiella pneumoniae. Other pathogens associated with the occurrence of endometritis in mares are yeasts and fungi, particularly in mares with reduced resistance, or as a sequela of exuberant antimicrobial therapy. Some mares appear particularly susceptible to postbreeding endometritis. These mares accumulate fluid in the uterine lumen after mating or insemination. In contrast, healthy mares have a vigorous but transient inflammatory response to mating, and the uterus rapidly regains the noninflamed status.

Visible exudate is rarely a feature of endometritis in mares. Endometrial inflammation is best confirmed by examination of endometrial cytologic or histologic evaluation. Ultrasonographic imaging of intraluminal free fluid, especially during diestrus, and isolation of potentially pathogenic bacteria from appropriately guarded swabs are additional diagnostic techniques. Because most causative organisms are common commensals, isolation of bacteria alone is not sufficient evidence for diagnosis. Nevertheless, evidence suggests that the fertility of mares is impaired if results of endometrial cytologic evaluation or culture are positive.

Intrauterine treatment for endometritis is still commonly used in mares. Many antimicrobial drugs have been used, and effective doses determined mainly empirically. Some examples include penicillin (5,000,000 U per mare, intrauterine; effective mainly against S zooepidemicus), ticarcillin (6 g per mare, intrauterine; provides broad-spectrum activity), ampicillin (3 g of soluble preparation per mare, intrauterine), gentamicin (2 g [buffered with bicarbonate] per mare, intrauterine; effective especially against gram-negative bacteria), and kanamycin (2 g per mare, intrauterine; effective against gram-negative bacteria). For fungal or yeast infections, amphotericin B (100 mg per mare, intrauterine) or clotrimazole (500 mg per mare, intrauterine) has been effective. Treatment should be continued for several consecutive days, preferably during estrus. Most of these endometritis treatments constitute extralabel drug use in the US. Postbreeding endometritis may be treated by uterine lavage or by the use of oxytocic drugs to rid the uterus of fluid.

Endometritis in sows is characterized by profuse purulent discharge 15–25 days after infection, during the subsequent proestrus or estrus. Infection may be of long duration, with signs recurring at each estrus.

Some sows recover from endometritis spontaneously, but there does not seem to be an effective treatment for those that do not. At necropsy, copious quantities of purulent exudate may be found in the uterus, making this condition more akin to pyometra.