Get access to all handy features included in the IVIS website
- Get unlimited access to books, proceedings and journals.
- Get access to a global catalogue of meetings, on-site and online courses, webinars and educational videos.
- Bookmark your favorite articles in My Library for future reading.
- Save future meetings and courses in My Calendar and My e-Learning.
- Ask authors questions and read what others have to say.
What to Do with the Problem Mare: New Approaches for Diagnosis and Management
M.L. Macpherson
Get access to all handy features included in the IVIS website
- Get unlimited access to books, proceedings and journals.
- Get access to a global catalogue of meetings, on-site and online courses, webinars and educational videos.
- Bookmark your favorite articles in My Library for future reading.
- Save future meetings and courses in My Calendar and My e-Learning.
- Ask authors questions and read what others have to say.
Read
For the equine veterinarian, an open mare at the end of the breeding season is often a source of intense frustration. Several factors contribute to lack of pregnancy in mares including breeding management, mare age, perineal abnormalities, uterine pathologies, reproductive tract damage and stallion fertility. Sorting out the inciting cause(s) of infertility can be challenging. Traditional diagnostic tests and treatment approaches frequently address simple problems in mares. For the mare that fails to get pregnant after being well managed during the breeding season, additional measures may need to be taken. The aim of this paper is to discuss more recent approaches to diagnosing and/or managing challenging reproductive problems in the mare.
Initial Evaluation of the Mare
A mare traditionally presents for fertility evaluation after: 1. Mating to a known fertile stallion, over successive cycles, without resultant pregnancy; 2. Pregnancy loss; 3. A mare with known physical or behavioral reproductive abnormalities. The evaluation process always starts with an accurate history of both general and reproductive health, a full physical examination and a thorough examination of both the external and internal genitalia. Examination tools that are commonly used include evaluation of the perineal area, transrectal palpation and ultrasonography of the reproductive tract, sampling for uterine culture, cytology and endometrial biopsy and vaginal examination. Results from these tests helps with obvious, and often correctable, problems. The challenge lies in the mare without detectable reproductive pathology. A typical scenario would be the mare that has negative samples from uterine culture and cytology and no readily identifiable physical defects in the reproductive tract. The mare is often bred using good management techniques to a known fertile stallion, yet fails to get pregnant.
Transrectal Ultrasound Examination
Ultrasound examination is an important and useful component of evaluating reproductive health in mares. Intraluminal uterine fluid around the time of breeding and ovulation has an established relationship to reduced pregnancy rates in cycling and postpartum mares.1-3 Post-mating induced endometritis (PMIE) is the most common cause of uterine fluid accumulation in the periovulatory period of mares.4 Mares with delayed uterine clearance often have defects in intrinsic myometrial contractility5 as well as lymphatic stasis.6 The conditions frequently manifest themselves as intraluminal fluid accumulation and/or abnormal uterine edema patterns during estrus.7 Specifically, these mares often have an unusually large amount of uterine edema starting early in the estrus period and persisting after ovulation. Interestingly, mares with bacterial endometritis do not consistently develop intraluminal fluid. Recent studies8,9 reported that mares having uterine infections caused by E. coli were less likely to have intrauterine fluid accumulation identified by ultrasound and less evidence of cytologic inflammation. Mares with uterine infections caused by β hemolytic Streptococcus, Klebsiella pneumoniae, Enterobacter cloacae or yeast had a higher incidence of ultrasonographically detectable uterine fluid. These findings can be useful when determining the need for additional diagnostic tests.
Uterine Culture and Cytology
A culture and cytology of the mare’s endometrium should be performed to evaluate for potential endometritis as well as other cells that may indicate a problem. Uterine culture and cytology can be obtained from either a double guarded swab, cytology brush, endometrial biopsy, or low volume uterine lavage. Culture and cytology should be performed together, as either test has a high prevalence of false negatives when used alone. Since the vagina is not a sterile environment, false positive culture results are common due to contamination from the perineum or the vagina. Conversely, aerobic culture may fail to diagnose fungal or yeast infections, which are more easily seen on cytology. In general, any bacterial growth in conjunction with neutrophils on cytologic exam is diagnostic for uterine infection. In addition, pure growth of a single organism, particularly the common causes of endometritis should be considered diagnostic for infection even in the absence of positive cytology. Known reproductive pathogens in the mare include: Streptococcus equi zooepidemicus, Escherechia coli, Klebsiella pneumoniae and Pseudomonas aeruginosa. Furthermore, the presence of more than two neutrophils per high powered field is diagnostic for endometritis.10 However, it has been shown that infections with E. coli and Pseudomonas aeruginosa are not often seen in conjunction with a positive cytology. Therefore, growth of one of these pathogens warrants further investigation in the mare with a history of chronic subfertility. Procedures such as low volume uterine lavage can be helpful in identifying infectious endometritis due to gram negative organisms. Yeast or fungus can often be seen directly on microscopic examination of cytologic specimens.
Low Volume Uterine Lavage
Low-volume uterine lavage can be performed to obtain a more representative sample of the uterine contents. It has been postulated that this method allows for sample collection from the entire uterus vs an isolated area.11 The method has been well described using practical methodology.12 Low volume lavage is best performed during diestrus to allow complete dilation of endometrial folds. When the technique is performed during estrus, fluid tends to collect in between edematous endometrial folds and can be difficult to retrieve. After fecal evacuation and preparation of the perineal area, a sterile Foley type catheter is aseptically inserted through the cervix, and into a uterine horn. 150-250 ml of sterile saline, lactated Ringer’s solution (LRS) or phosphate-buffered saline (PBS) is infused into the uterus. The fluid is agitated in the uterus through rectal massage for at least one minute. Oxytocin (10-12 IU, IV) is administered to promote uterine contractility for fluid collection. Fluid is moved to the tip of the uterine horn with the catheter using transrectal uterine manipulation. With the operator’s hand cradling the tip of the uterine horn around the catheter, the fluid is allowed to drain out through the catheter and back into the bag so that the system remains “closed.” Fluid is then transferred into 50 ml conical tubes. A minimum of 50 ml of efflux is needed for accurate representation of uterine contents. The clarity of the fluid is evaluated for mucus strains and cloudy contents which may indicate endometritis. In one study,13 cloudy and mucus effluxes were highly correlated with presence of microorganisms (E. coli and β hemolytic streptococcus). Prior to culture and cytology, the contents are allowed to settle for at least 1 hour or the tube (s) are centrifuged for 10 min at 400 x g. Determining g force on a standard bench top centrifuge can be done with a nomograph and is well described by Vanderwall.14 After processing, fluid is decanted (if centrifuged) or aspirated (if allowed to settle) leaving 5 ml of supernatant and the pelleted cells. Two sterile cotton swabs are used to obtain samples from the pellet. One sample is placed in transport media for bacterial culture and the second sample is smeared directly on a slide for cytological evaluation. It is recommended that lavage fluid be processed within 8 hours of collection because saline is not conducive to bacterial preservation.15
[...]
Get access to all handy features included in the IVIS website
- Get unlimited access to books, proceedings and journals.
- Get access to a global catalogue of meetings, on-site and online courses, webinars and educational videos.
- Bookmark your favorite articles in My Library for future reading.
- Save future meetings and courses in My Calendar and My e-Learning.
- Ask authors questions and read what others have to say.
Comments (0)
Ask the author
0 comments