K. Satué and J.C. Gardon

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/63741

#### **Abstract**

In cyclic mares, the uterine environment can easily disturbed due to inflammatory proc‐ esses that occur secondary to microbial invasion. Different aerobic and anaerobic bacteria can enter the uterus during natural mating, artificial insemination, reproductive examina‐ tion or parturition. The postpartum period is a critical phase since due to relaxation of the uterus and cervix may favor recurrent infections air intake (pneumovagina) or urine col‐ lection in mares with poor perineal conformation. Infections are mainly caused by oppor‐ tunistic or commensal microorganisms, such as *Streptococcus zooepidemicus, hemolytic Escherichia coli* and *Staphylococcus aureus*. Other microorganisms like *Taylorella equigenita‐ lis, Klebsiella pneumoniae* and *Pseudomona aeruginosa* are transmitted through venereal route. Regarding to the fungal endometritis, the most common fungi include *Candida* and *Aspergillus*. These microorganisms cause infertility as a result of repeated inseminations during the breeding season and proliferate when the natural immune system is weak‐ ened in mares with advanced age and multiparous, or after repeated use of antibiotics. Indeed, in susceptible mare to endometritis, uterine defense mechanisms involving phag‐ ocytosis and opsonization by neutrophils, local synthesis of antibodies, mucociliary activ‐ ity, vascular and myoelectric activity permeability are compromised, leading to fluid accumulation in response to inflammation and infertility.

**Keywords:** cycling mare, infectious diseases, reproduction

#### **1. Introduction**

The ability to maintain a uterine environment compatible with embryonic and fetal life is essential for reproductive efficiency in horses. However, the uterine environment is easily disturbed by an inflammatory process following aerobic and anaerobic bacterial invasion, which can occur during natural breeding, artificial insemination (AI), reproductive examina‐ tion, parturition, postnatal infection (pneumovaginal infections), and mostly during a delayed postnatal cleaning of the uterus as a result of poor conformation [1].

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These bacterial uterine infections cause conception and embryo survival failures despite many repeated breeding during the season. In the horse industry, endometritis due to uterine infectious of bacterial origin brings about 25–60% economic losses, leading to infertility. In pregnant mares, these infectious diseases can appear as failure to conceive, early fetal losses, mid-gestational abortion, placentitis, birth of a septic neonate, postpartum metritis, or delays in rebreeding and can be related with other systemic pathologies of viral, bacterial, and fungal origin [2]. Besides in nonpregnant mares, these infections are most often caused by opportun‐ istic or commensal and venereal microorganisms, with a large variety of species have been isolated.

The healthy mare has three functional genital seals forming a barrier between the external environment and the uterine lumen [3, 4].


If the closure of the vulva is compromised, it results in the development of a pneumovagina with consequent aspiration of bacteria and other contaminated products [5]. The initial development of vaginitis can result in cervicitis and acute endometritis and therefore can lead subfertility. Usually, in mares, contamination of the caudal reproductive tract with bacteria during pregnancy can result in embryonic death. In late pregnancy, it can result in the development of placentitis and abortion [4, 6].

The more severe conformational abnormalities result in failure of the vulval closing, increasing fecal contamination since the vulva forms a platform in which feces can collect. In these cases, the vulval lips are angled at 25° for even 50° to the vertical. According to Bradecamp [6], defective vulval conformation can be:

**•** Congenital, rare to find.

These bacterial uterine infections cause conception and embryo survival failures despite many repeated breeding during the season. In the horse industry, endometritis due to uterine infectious of bacterial origin brings about 25–60% economic losses, leading to infertility. In pregnant mares, these infectious diseases can appear as failure to conceive, early fetal losses, mid-gestational abortion, placentitis, birth of a septic neonate, postpartum metritis, or delays in rebreeding and can be related with other systemic pathologies of viral, bacterial, and fungal origin [2]. Besides in nonpregnant mares, these infections are most often caused by opportun‐ istic or commensal and venereal microorganisms, with a large variety of species have been

The healthy mare has three functional genital seals forming a barrier between the external

**•** Lips of vulva: examination of vulvar and perineal conformation should be included in all prebreeding examinations or evaluations for infertility. The vulva should be a vertical position aligned with the anal opening. The labia should be tight, with most of length below the tuber ischii. The vulvar lips may become parted as a consequence of malformation caused by previous traumatic injuries. In older multiparous mares, there is a tendency for extreme relaxation of the vulvar lips, particularly during estrus, as well as tilting of the dorsal aspect of the vulva becomes horizontal as it is pulled cranially over the tuber ischii. These anatomic changes predispose the mare to pneumavagina (windsucking) and pneu‐ mouterus, ultimately causing urine to pool in the cranial vagina producing ascending infection and contaminate the uterus when the cervix is open. Pneumovagina may lead to an urovagina (urine pooling within the vagina) when the vestibule and urethral opening are displaced cranially. In this situation, contamination with fecal material adds to the

**•** Vulvovaginal constriction: immediately in front of the external urethral opening is the vulvovaginal constriction or vestibular seal. In genitally healthy mares, this forms the second line of defense against aspirated air and fecal material. In a normal mare, the vestibulovaginal area remains sealed even when the vulvar labia are parted. Compromised vestibulovaginal sphincter function is suspected when air is sucked into the vagina of

**•** Cervix: forms the important third (and last) protective physical barrier to protect the uterus from the external environment. The cervix must also relax during estrus to allow intrauter‐ ine ejaculation or insemination of semen and drainage of uterine fluid, late pregnancy, and the immediate postpartum period. An inflammation of the cervix is usually associated with

If the closure of the vulva is compromised, it results in the development of a pneumovagina with consequent aspiration of bacteria and other contaminated products [5]. The initial development of vaginitis can result in cervicitis and acute endometritis and therefore can lead subfertility. Usually, in mares, contamination of the caudal reproductive tract with bacteria during pregnancy can result in embryonic death. In late pregnancy, it can result in the

compromised secondary to rectovaginal tears and other foaling injuries.

isolated.

258 Genital Infections and Infertility

environment and the uterine lumen [3, 4].

increased risk of infection.

endometritis and/or vaginitis.

development of placentitis and abortion [4, 6].

**•** Acquired, which is due to vulval enlarging resulting for the repeated foaling, injury to perineal tissue and poor body condition (old, thin mares). Older and pluriparous mares are frequently affected with pneumovagina. However, in cases of young mares that are in work and have little body fat and/or poor vulval conformation, it can develop these pathology.

Pneumovagina might occur during estrus when the perineal tissues are more relaxed. Some mares make a noise while walking; however, the diagnosis of other mares may be difficult by the absence of noises. The pathognomonic sign is the presence of hyperemia and a frothy exudate in the anterior vagina, on examination with a speculum. Poor cervical dilation may reduce uterine clearance, while cervical damage or incompetence may predispose to infection. Finally, susceptible mares may accumulate more fluid within their uterus than normal mares because of a greater production of glandular secretions secondary to inflammation. The consequence of decreased physical clearance is that bacteria, inflammatory by-products and fluid remain in the uterine lumen, inducing more inflammation, mucosal cell damage, and fibrosis. The persistent inflammation may result in premature luteolysis. Ultimately, chronic inflammation results in degenerative changes within the endometrium and reduced fertility [5–7].

Real-time ultrasound examination of the uterus may reveal the presence of air or urine as hyperechoic or hypoechoic foci seen at the opposed luminal surfaces, respectively. Cytological and histological examination of the endometrium may demonstrate significant numbers of neutrophils indicative of an endometritis [6]. The clinical presentation of acute or chronic reproductive tract infections in the mare is salpingitis, cervicitis, and vaginitis [2, 5].
