Reproductive Tract Microbiota of Mares.

The female reproductive tract microbiota is a complex community of microorganisms that might be crucial in maintaining a healthy reproductive environment. Imbalances in the bacterial community (dysbiosis) and the reduction of beneficial organisms and pathogen proliferation are associated with disease. Endometritis is a common cause of fertility problems in mares, and it is still challenging to diagnose and treat based on routine culture results of certain microorganisms. Although high-throughput sequencing studies provide helpful information regarding the composition of the reproductive tract microbiota in mares, there are still challenges in defining a "normal" microbiota. The primary objective of this literature review is to summarize the current knowledge regarding the microbiota present in the reproductive tract of mares, including the vagina, cervix, and uterus. The second objective is to describe the relevant factors that can impact the reproductive microbiota of mares, including the estrous cycle stage, the type of species (genera) investigated, season, and geographic location. The rationality of identifying the normal microbiota in the reproductive tract of a mare will likely aid in understanding the impact of the microbiota on the host's reproductive health and contribute to the treatment and prevention of equine sub and infertility issues.

Vaginal and Uterine Microbiota of Healthy Maiden Mares during Estrus.

This descriptive cross-sectional study compared the microbiota of the uterus, vagina, clitoral fossa (CF), and perineal skin in healthy maiden mares during estrus. Twelve synchronized, healthy maiden mares (3-4 years old) from one single recipient mare herd were included. Microbial communities were characterized by amplifying the V3-V4 region of the 16S rRNA gene using the Illumina MiSeq platform. The uterine and vaginal microbiota had significantly lower richness (Chao-1) than the skin (p < 0.05). The uterine and vagina bacterial composition was similar in presence and abundance and could be differentiated from that of the CF and perineal skin. The microbial composition (Jaccard and Bray-Curtis distances) significantly differed across body-site locations (p < 0.05), which explained approximately 14% and 19% of the variation in microbial composition for Jaccard and Bray-Curtis distances, respectively. Firmicutes, Actinobacteria, Proteobacteria, and Bacteroidetes were the dominant taxa in the uterus and vagina, with higher proportions of Proteobacteria in the vaginal samples compared to the uterine samples. Streptococcaceae and Staphylococcaceae were present in high abundance in the uterine and vaginal samples, while Lactobacillaceae were not (<10%). We demonstrate that the uterine and vaginal microbiota of healthy maiden mares during estrus is similar but both distinct from that of the CF and perineal skin.

Dynamics of the Equine Placental DNA Methylome and Transcriptome from Mid- to Late Gestation.

The placenta is a temporary organ that is essential for the survival of the fetus, with a lifelong effect on the health of both the offspring and the dam. The functions of the placenta are controlled by its dynamic gene expression during gestation. In this study, we aimed to investigate the equine placental DNA methylome as one of the fundamental mechanisms that controls the gene expression dynamic. Chorioallantois samples from four (4M), six (6M), and ten (10M) months of gestation were used to map the methylation pattern of the placenta. Globally, methylation levels increased toward the end of gestation. We identified 921 differentially methylated regions (DMRs) between 4M and 6M, 1225 DMRs between 4M and 10M, and 1026 DMRs between 6M and 10M. A total of 817 genes carried DMRs comparing 4M and 6M, 978 comparing 4M and 10M, and 804 comparing 6M and 10M. We compared the transcriptomes between the samples and found 1381 differentially expressed genes (DEGs) when comparing 4M and 6M, 1428 DEGs between 4M and 10M, and 741 DEGs between 6M and 10M. Finally, we overlapped the DEGs and genes carrying DMRs (DMRs-DEGs). Genes exhibiting (a) higher expression, low methylation and (b) low expression, high methylation at different time points were identified. The majority of these DMRs-DEGs were located in introns (48.4%), promoters (25.8%), and exons (17.7%) and were involved in changes in the extracellular matrix; regulation of epithelial cell migration; vascularization; and regulation of minerals, glucose, and metabolites, among other factors. Overall, this is the first report highlighting the dynamics in the equine placenta methylome during normal pregnancy. The findings presented serve as a foundation for future studies on the impact of abnormal methylation on the outcomes of equine pregnancies.

Effect of Transvaginal Aspiration of Oocytes on Blood And Peritoneal Fluid Parameters in Mares.

Transvaginal aspiration of oocytes (TVA) is a commonly used clinical procedure to obtain oocytes for in vitro production of embryos in horses. The goal of this study was to evaluate the effect of the TVA procedure on blood and peritoneal parameters, and to investigate the association of these findings with variables such as use of antibiotics, number of ovarian punctures, and length of the procedure. Physical examination was performed and blood and peritoneal fluid were obtained from 14 mares before they underwent TVA and the same parameters were assessed 24 hours after the procedure. On examination, 13/14 mares remained clinically healthy after the procedure. One mare developed low-grade fever, transient anorexia and mild colic that resolved within 12 hours post-TVA. The use of antibiotics, length of procedure and number of ovarian punctures did not have an effect on the measured parameters. All the mares presented significant changes in the leukogram, but these mostly remained within normal reference range values. The peritoneal parameters were also consistently affected after TVA. A significant post-TVA increase in lactate, total protein, and peritoneal neutrophil count was observed in peritoneal fluid. Peritoneal lactate level was elevated above baseline physiological levels in more than 50% of the mares. Results from this study indicate that there is an expected degree of inflammation after TVA procedures and peritoneal fluid parameters could be successfully used to monitor inflammation in the early stages.

Fungal Placentitis Caused by Aspergillus terreus in a Mare: Case Report.

Placentitis has been reported as the most important cause of equine abortions, stillbirths, and perinatal deaths in horses. Most cases are caused by bacteria and less commonly by fungal elements. The aim of this report is to describe the clinical presentation of a fungal placentitis caused by Aspergillus terrerus. A 5-year-old thoroughbred maiden mare at the 217th day of gestation presented with some classic signs of placentitis (premature udder development and milk dripping). All ultrasonographic findings were consistent with a live fetus and a severe placentitis. On vaginal examination, purulent discharge was found coming from the external cervical os. Samples sent for culture yielded very small numbers of mixed growth including Enterococcus faecalis (by matrix-assisted laser desorption/ionization time-of-flight mass spectrometer), Streptococcus viridans, and Aspergillus terreus, and polymerase chain reaction was positive for Aspergillus terreus and Pseudomonas. The mare was placed on broad-spectrum antimicrobials, nonsteroidal anti-inflammatories, and hormonal and antifungal treatment. The fetus kept on developing and growing despite the placentitis for 14 days until the demise of the fetus in utero occurred. Aspergillus terreus was isolated from the chorionic surface but not from the fetus. Fungal placentitis is not very commonly found in mares. The extent of the placental lesions and the severity of the placentitis contributed to the death of the fetus. This is one of the few case reports available describing fungal placentitis. Aspergillus terreus has not been previously reported as a cause of placentitis.