Treatment strategies for mares with placentitis

Diagnosis and management of placentitis with severe funisitis in a multiparous Warmblood mare

Placentitis is an important cause of reproductive losses in the equine industry. Many cases of clinical placentitis are not diagnosed until late in the course of the disease, and for this reason there is variability in the timing of intervention, diagnostic measurements, and treatment protocols. An 8-year-old multiparous Dutch Warmblood mare that was recently exposed to EHV-1 in the herd of origin presented for routine foaling management. Placentitis was diagnosed upon intake, and medical treatment was initiated. The mare delivered a term foal, and diagnostics for infectious etiology were unrewarding. While there were obvious clinical signs supporting a diagnosis of placentitis, histopathologic examination did not reveal active inflammatory lesions in the chorioallantois; however, severe funisitis was present. This report reviews early diagnosis and management of placentitis, demonstrates an array of classic and subtle pathologic lesions seen on microscopic examination, and discusses pathophysiology of placentitis.

Metagenetic Analysis of the Pregnant Microbiome in Horses

Placentitis is the leading cause of infectious abortion in the horse. Additionally, it can result in weak and/or growth restricted offspring. While the etiology of ascending placentitis is well described in mares, less is known regarding the pathogenesis of other types, such as nocardioform placentitis. This study aims to identify the microbial communities in different body sites of the pregnant mare in early gestation to establish a core microbiome that may be perturbed in pathologic pregnancies such as placentitis. We hypothesize that the equine placenta harbors a distinct resident microbiome in early pregnancy when characterized by metagenetics and that there will be a disparity in bacterial communities from the oral, vaginal, and fecal microbiome. Samples were collected from the oral cavity, vagina, anus, and the allantoic portion of the allantochorion ("placenta") from five pregnant mares between 96 and 120 days of gestation. The V4 region of the 16S rRNA gene was amplified for Illumina MiSeq sequencing to examine core bacterial communities present in the different body sites. Microbial community composition of the pregnant ponies by body site was significantly different (Bray-Curtis dissimilarity). The placenta was significantly different from the feces, oral cavity, and vagina. Alpha diversity measuring the Shannon diversity matrix was significant, with the body sites being a compounding variable, meaning there was a difference in richness and evenness in the different microbial communities. Feces had the greatest alpha diversity, while the oral cavity and placenta similarly had the least. In conclusion, metagenetics did reveal distinct community differences in the oral, fecal, vaginal, and placenta cavities of the horse. The equine placenta does show similarities in its microbial communities to the oral cavity. Further research needs to be completed to investigate how bacteria may be translocated to the placenta from these other body sites and how they contribute to the development of placentitis.

Dystocia in the Standardbred Mare: A Retrospective Study from 2004 to 2020

Dystocia as a prolonged stage II parturition (>30 min) was associated with a higher risk of complications. The hypothesis of the study was that any type of dystocia could affect the foal’s health, even when the stage II was <30 min. Clinical reports on 222 Standardbred mares and their foals hospitalized at the Veterinary Teaching Hospital of the University of Bologna from 2004 to 2020 were reviewed. Mares were divided into the Eutocia Group (165, eutocic delivery) and the Dystocia Group (57, dystocic delivery). The incidence of dystocia was 4.9%. Stage II was longer in the Dystocia Group (median 20 min) than in the Eutocia Group (median 12 min). All occurrences of dystocia were retrospectively classified into three categories of severity: mild, moderate and severe dystocia. The occurrence of postpartum complications in mares and neonatal diseases and failure of passive transfer of immunity in foals was higher in the Dystocia Group. Foal venous lactatemia and serum creatine kinase were significantly higher in the Dystocia Group (median 3.9 mmol/L; 262 UI/L respectively) than in the Eutocia Group (median 3.1 mmol/L; 187 UI/L respectively). The APGAR score was lower in the Dystocia Group (median 8) than in the Eutocia Group (median 10) and significantly lower in severe dystocia (median 3). The duration of stage II should not be considered the only parameter of dystocia in mares: even a rapid resolution of dystocia could pose health risks to the foal and the mare.

Managing Reproduction Emergencies in the Field: Part 1: Injuries in Stallions; Injury of the External Portion of the Reproductive Tract and Gestational Conditions in the Mare

Selected emergency conditions of male and female reproductive tracts in horses are described, including injuries affecting the external genitalia of male horses and emergent conditions arising during gestation in mares. Conditions affecting male horses are discussed in the context of breeding stallions, but kicks or other mechanisms of trauma in the groin can also affect geldings. Priapism, paraphimosis, trauma to the scrotum and testicles, and penile injury are discussed. In mares, traumatic vestibular injury, placentitis, hydropsic conditions, prepubic tendon and abdominal wall compromise, and uterine torsion are included. Clinical recognition of the problem, diagnostic procedures, and treatments are summarized.

Alterations of Circulating Biomarkers During Late Term Pregnancy Complications in the Horse Part II: Steroid Hormones and Alpha-Fetoprotein

Preterm labor and/or abortion causes considerable economic impact on the equine industry. Unfortunately, few experimental models exist for the induction of various pregnancy-related complications, and therefore extrapolations are made from the experimental model for ascending placentits, although inferences may be minimal. Certain steroid hormones (progestogens, estrogens) and fetal proteins (alpha-fetoprotein; AFP) might improve the diagnostics for abnormal pregnancy, but the utility of these markers in the field is unknown. To assess this, thoroughbred mares (n = 702) were bled weekly beginning in December 2013 until parturition/abortion. Following parturition, fetal membranes were assessed histopathologically and classified as either ascending placentitis (n = 6), focal mucoid placentitis (n = 6), idiopathic abortion (n = 6) or no disease (n = 20). Weekly serum samples were analyzed for concentrations of progesterone, estradiol-17β, and AFP. Samples were analyzed retrospectively from the week of parturition/abortion in addition to the preceding four weeks. For both ascending and focal mucoid placentitis, a significant increase in progesterone and AFP was noted, alongside a significant decrease in estradiol-17β and the ratio of estradiol-17β to progesterone in comparison to controls. In contrast, idiopathic abortions experienced a decrease in progesterone concentrations alongside an increase in AFP, and this was only noted in the week preceding parturition/abortion. In conclusion, spontaneous placental infection in the horse altered both endocrine and feto-secretory markers in maternal circulation, while minimal changes were noted preceding noninfectious idiopathic abortion. Additionally, this is the first study to report an alteration in steroid hormones and AFP during the disease process of focal mucoid placentitis, the etiology of which includes Nocardioform placentitis.

Transcriptomic analysis of equine placenta reveals key regulators and pathways involved in ascending placentitis†

Improved understanding of the molecular mechanisms underlying ascending equine placentitis holds the potential for the development of new diagnostic tools and therapies to forestall placentitis-induced preterm labor. The current study characterized the equine placental transcriptome (chorioallantois [CA] and endometrium [EN]) during placentitis (placentitis group, n = 6) in comparison to gestationally-matched controls (control group, n = 6). Transcriptome analysis identified 2953 and 805 differentially expressed genes in CA and EN during placentitis, respectively. Upstream regulator analysis revealed the central role of toll-like receptors (TLRs) in triggering the inflammatory signaling, and consequent immune-cell chemotaxis. Placentitis was associated with the upregulation of matrix metalloproteinase (MMP1, MMP2, and MMP9) and apoptosis-related genes such as caspases (CASP3, CASP4, and CASP7) in CA. Also, placentitis was associated with downregulation of transcripts coding for proteins essential for placental steroidogenesis (SRD5A1 and AKR1C1), progestin signaling (PGRMC1 and PXR) angiogenesis (VEGFA, VEGFR2, and VEGFR3), and nutrient transport (GLUT12 and SLC1A4), as well as upregulation of hypoxia-related genes (HIF1A and EGLN3), which could explain placental insufficiency during placentitis. Placentitis was also associated with aberrant expression of several placenta-regulatory genes, such as PLAC8, PAPPA, LGALS1, ABCG2, GCM1, and TEPP, which could negatively affect placental functions. In conclusion, our findings revealed for the first time the key regulators and mechanisms underlying placental inflammation, separation, and insufficiency during equine placentitis, which might lead to the development of efficacious therapies or diagnostic aids by targeting the key molecular pathways.

Pharmacokinetics of Intrarectal Altrenogest in Horses

Hospitalized pregnant mares being held nil per os (PO) because of medical or surgical events present a dilemma for pregnancy maintenance therapy, which commonly includes oral altrenogest. Rectal administration of medications is a recognized route for achieving systemic concentrations, but there are no data on the pharmacokinetics of rectal altrenogest administration in horses. The purpose of this study was to determine the pharmacokinetics of altrenogest following PO or per rectum (PR) administration in mares. Using a randomized two-way crossover study design, six horses received altrenogest (0.088 mg/kg; PO or PR q 24 hours for 5 days), with a 7-day washout period, and the concentrations of altrenogest were determined by an ultrahigh performance liquid chromatography with tandem mass spectrometry. Plasma concentrations persisted above presumed therapeutic concentrations for a mean of 36 hours (range 24-72 hours) and 5.5 hours (range 3-8 hours) for PO and PR administration, respectively. The calculated half-life (T ½) of PO administration (7.01 ± 3.13 hours) was correspondingly increased when compared to PR administration (2.82 ± 1.07 hours). Relative bioavailability of altrenogest following PR administration was only 5.47%. Altrenogest is rapidly absorbed following PR administration in the horse and reaches therapeutic concentrations, making this a viable method of treatment in NPO mares. The decreased bioavailability and shorter detection time suggest 0.088 mg/kg PR q 4-8 hours would be necessary to maintain therapeutic concentrations over a 24-hour period.

A clinical case of equine fungal placentitis with reference to hormone profiles and ultrasonography

Fungal placentitis is an infectious disease inducing abortion in pregnant mares. In the present report, we describe a field case of abortion caused by fungal placentitis with consecutive examinations. The progesterone level and combined thickness of the uterus and placenta (CTUP) were abnormal before the onset of clinical signs. Additionally, the estradiol level started to change before the appearance of clinical signs. Abnormal serum amyloid A values and an abnormal fetal heart rate were observed after the onset of clinical signs. The present report demonstrates that the progesterone level and CTUP may be adequate as early diagnostic markers of fungal placentitis and bacterial infection. Endocrinological evaluation based on cutoff values or serial measurements were also useful for early diagnosis.

Ultrasonographic evaluation of equine fetal growth throughout gestation in normal mares using a convex transducer

It has not been common to perform regular ultrasound examination of the fetus in equine practice, due to the increasing volume of the uterus caused by fetal development. The convex three-dimensional transducer is bulb-shaped and is able to observe wide areas. In addition, its operation is simple, making it easy to create appropriate angles for various indices using a transrectal approach. The aim of this study was to measure Thoroughbred fetal growth indices throughout gestation using a convex transducer and to clarify the detectable period of some indices for clinical use. We demonstrated changes in fetal indices, such as crown rump length (CRL), fetal heart rate (FHR), fetal eye and kidney and the combined thickness of uterus and placenta (CTUP). CTUP increased from 30 weeks of gestation, and FHR peaked at 8 weeks and then decreased to term. CRL could be observed until 13 weeks due to its wide angle, longer than in previous reports. Fetal eye and kidney could be observed from 10 and 28 weeks, respectively, and these increased with pregnancy progress. The present results showed the advantage of transrectal examination using a convex transducer for evaluation of normal fetal development. Although ultrasonographic examination in mid- to late-gestation is not common in equine reproductive practice, our comprehensive results would be a useful basis for equine pregnancy examination.

Ascending placentitis in the mare: A review

Ascending placentitis is a condition that occurs late in pregnancy when bacteria enter the sterile uterus from the lower reproductive tract. It leads to abortion or the birth of premature and weakened foals. Early detection and treatment of this condition is vital for ensuring the production of a viable foal.

Mares with ascending placentitis often present in late term pregnancy with signs of premature udder development and premature lactation. There may be a vulvar discharge. Early detection of placental problems is possible using trans-abdominal or trans-rectal ultrasonography. Hormones such as progesterone and relaxin may be measured as indicators of foetal stress and placental failure. Postpartum foetal membranes may be thickened and contain a fibronecrotic exudate. The region most affected is the cervical star. Definitive diagnosis of ascending placentitis is by histopathological examination of the chorioallantoic membrane.

Ideal treatment strategies are aimed at curing the infection and prolonging the pregnancy to as close to term as possible and consist of anti-microbials, anti-inflammatories and hormonal support.

Swabs are taken from affected mares to determine antibiotic sensitivity and to aid in treatment of foals born from these mares which are at risk of becoming septic. If detected early enough, the chances of producing a viable foal are greatly increased.

Hormone Profiles and Treatments in the Late Pregnant Mare

Evaluation of hormone profiles in late pregnancy is one of the major determinants of fetoplacental compromise in equine clinical practice. Use of hormone therapies is subjective and reflects, to a large extent, our lack of understanding about the endocrine relations between the mare, placenta, and fetus. This article describes the normal endocrine events in late gestation, the abnormal hormone patterns associated with fetoplacental dysfunction, and the hormone interventions that are currently used or could be used to improve pregnancy outcome.

Reproductive Tract Infections in Horses

Diagnosis, treatment, and, ultimately, prevention of reproductive disease are vital components of equine veterinary medicine. A thorough understanding of anatomy and physiology is necessary to reconcile the pathologic findings of disease. Only then can a rational treatment plan be formulated. Many recent advances in knowledge about the reproductive system of multiple species have application to the mare and stallion.