Clinical and Subclinical Endometritis in the Mare: Both Threats to Fertility

Abstract

Endometritis, a major cause of mare infertility arising from failure to remove bacteria, spermatozoa and inflammatory exudate post-breeding, is often undiagnosed. Defects in genital anatomy, myometrial contractions, lymphatic drainage, mucociliary clearance, cervical function, plus vascular degeneration and inflamm-ageing underlie susceptibility to endometritis. Diagnosis is made through detecting uterine fluid, vaginitis, vaginal discharge, short inter-oestrous intervals, inflammatory uterine cytology and positive uterine culture. However, these signs may be absent in subclinical cases. Hypersecretion of an irritating, watery, neutrophilic exudate underlies classic, easy-to-detect streptococcal endometritis. In contrast, biofilm production, tenacious exudate and focal infection may characterize subclinical endometritis, commonly caused by Gram-negative organisms, fungi and staphylococci. Signs of subclinical endometritis include excessive oedema post-mating and a white line between endometrial folds on ultrasound. In addition, cultures of uterine biopsy tissue or of small volume uterine lavage are twice as sensitive as guarded swabs in detecting Gram-negative organisms, while uterine cytology is twice as sensitive as culture in detecting endometritis. Uterine biopsy may detect deep inflammatory and degenerative changes, such as disruption of the elastic fibres of uterine vessels (elastosis), while endoscopy reveals focal lesions invisible on ultrasound. Mares with subclinical endometritis require careful monitoring by ultrasound post-breeding. Treatments that may be added to traditional therapies, such as post-breeding uterine lavage, oxytocin and intrauterine antibiotics, include lavage 1-h before mating, carbetocin, cloprostenol, cervical dilators, systemic antibiotics, intrauterine chelators (EDTA-Tris), mucolytics (DMSO, kerosene, N-acetylcysteine), corticosteroids (prednisolone, dexamethasone) and immunomodulators (cell wall extracts of Mycobacterium phlei and Propionibacterium acnes).

Accuracy of different endometrial swabbing techniques in the mare

“…Clinical findings are substantiated by inflammatory uterine cytology (Knudsen 1964, Wingfield Digby and Ricketts 1982, Riddle et al 2007, Leblanc and Causey 2009 and positive uterine culture (Dimmock and Edwards 1923, Brook 1984, Riddle et al 2007). Collecting samples from the uterus is a routine practice in the assessment of uterine health.…”

Evaluation of the reproductive and metabolic problems encountered during two breeding seasons in barren Arabian mares

“…Ovarian activity disorders that may cause infertility should be evaluated, and pathological changes in the reproductive organs, such as intrauterine fluid accumulation, can be detected during an ultrasonographic examination (2). Endometritis, which is one of the major causes of infertility in mares, is caused by inadequate bacterial inhibition, spermatozoa removal from the uterus, and inflammatory exudates after breeding (3). Although clinical endometritis is diagnosed easily, uterine culture, cytology, and endometrial biopsy are important tools along with ultrasonography examination that enable diagnosis of subclinical cases of endometritis (3).…”

“…Endometritis, which is one of the major causes of infertility in mares, is caused by inadequate bacterial inhibition, spermatozoa removal from the uterus, and inflammatory exudates after breeding (3). Although clinical endometritis is diagnosed easily, uterine culture, cytology, and endometrial biopsy are important tools along with ultrasonography examination that enable diagnosis of subclinical cases of endometritis (3). Previous studies have suggested that only uterine cytology or bacteriology (4) or a combination of both (4,5) can be used to determine uterus inflammation.…”

“…In addition, various studies have also shown that uterine cytology and bacteria collected at the beginning of the season (before breeding) might affect the success rate of pregnancy and foaling (4,6). Degenerative changes, which are determined by endometrial biopsy, are also associated with the diagnosis of subclinical endometritis in mares as well as treatment success (3).…”

Non-traditional treatments for endometritis in mares

“…Failure to remove bacteria, spermatozoa and inflammatory exudate post-breeding may lead to inflammation of endometrium. Moreover, the factors which underlie susceptibility to endometritis are: defects in genital anatomy, impaired myometrial contractions, impaired immune defense, overproduction of mucus and inadequate lymphatic drainage, abnormal mucociliary clearance and cervical function (Watson, 2000;LeBlanc & Causey, 2009;LeBlanc, 2010). Uterine inflammation has been proposed as a mechanism for impaired myometrial contractility and accumulation of inflammatory products in the uterine lumen (Troedsson et al, 1993;Troedsson, 1999).…”