General and comparative aspects of endometritis in domestic species: A review

Abstract

Endometritis is a leading cause of sub‐ and infertility in domestic animal species. The healthy uterus is colonized by commensal bacteria, viruses and yeast/fungi that represent the nonpathogenic microbiota. A shift in the number or type of organisms accompanied by immune dysfunction, however, may trigger uterine infection and inflammation. Metritis is associated with inflammation of all uterine layers (endometrium, myometrium and perimetrium), whereas endometritis is a more superficial inflammation involving solely the endometrium. Endometritis generally occurs at two time points in domestic animal species, postpartum and postmating. Postpartum endometritis may chronically persist, either as a low‐grade disease that often manifests as a vaginal discharge but not a systemic illness (in some species termed clinical endometritis) or sometimes subclinical where features are only detected by endometrial sampling. Contamination of the uterus at the time of mating occurs by direct deposition of semen (ejaculated or artificially inseminated) into the uterus. Improper drainage of the ejaculatory fluid or an inadequate immune response may result in persistent mating‐induced endometritis. Both postpartum and postmating endometritis interferes with fertility by creating a suboptimal environment for embryo development and placentation, and chronic endometritis may have an impact on sperm survival and fertilization ability. In the postpartum animal, there may also be changes in milk production and maternal behaviour, which can affect offspring health and survival. Preventive strategies for endometritis largely depend on monitoring their known risk factors, which are sometimes specific with regard to the species. Effective, nonantibiotic therapy for endometritis is not available to date. Overall, extensive research has been performed in cattle and horses to unravel key aspects of endometritis, but in sows and bitches, the available literature is scant. Thus, the need and opportunity to investigate the condition vary considerably among domestic species and necessitate their comparative assessment. This article reviews general and comparative aspects of the diagnosis and classification, pathogenesis, preventive strategies and therapeutics of endometritis in domestic species with a specific focus on cows, mares, sows and bitches.

Investigation of Uterine Fluid Extracellular Vesicles’ Proteomic Profiles Provides Novel Diagnostic Biomarkers of Bovine Endometritis

“…In both species, the presence of endometritis without clear clinical manifestations poses a notable challenge, as its diagnosis is intricate. The impact of endometritis in cattle encompasses diminished conception rates, heightened embryo loss, and prolonged calving-to-conception intervals [ 48 ]. Similarly, in humans, endometritis is associated with compromised implantation and an elevated risk of miscarriage [ 9 ].…”

“…While bacterial dysbiosis and insufficient immune responses have been correlated with CLE, SE has not been linked to uterine dysbiosis. Instead, it has been shown to associate with negative energy balance [ 48 ]. Researchers have established a connection between inadequate adaptation to negative energy balance and impaired regulation of inflammation [ 64 , 65 ].…”

Immune Regulation of Seminal Plasma on the Endometrial Microenvironment: Physiological and Pathological Conditions

“…Transient endometritis that occurs after mating is normal and can be caused by infectious factors (bacteria and fungi) or non-infectious factors (sperm) [167]. In species such as horses, pigs, and dogs, the lack of a cervical barrier and the deposition of large amounts of semen in the uterus are more likely to interfere with the uterine immune response and microbiome, resulting in persistent endometritis [168]. SP exhibits both anti-inflammatory and pro-inflammatory properties in regulating endometritis.…”

Reproductive Tract Microbial Transitions from Late Gestation to Early Postpartum Using 16S rRNA Metagenetic Profiling in First-Pregnancy Heifers

“…This phenomenon is particularly pertinent for primigravid females, as this is their first-ever parturition. In dairy cows, postpartum uterine contamination has been documented in nearly 100% of animals [7][8][9], and the same was suggested in humans and other mammals [2,[10][11][12]. Moreover, in dairy cows and women, postpartum uterine inflammatory diseases are more prevalent among primiparous than multiparous females [13][14][15].…”