Pneumovagina - Horses
Also Known As – Wind-sucking - Windsuckers - Vulvar Conformation
Sequelae – Placentitis – Endometritis – Vaginitis - Abortion
Introduction
Pneumovagina is usually a result of poor vulvar conformation in mares. It can be a significant contributor to ascending infection which can prevent establishment and survival of pregnancies.
Distribution
Worldwide
Signalment
A vulval angle of 80⁰ to the horizontal is ideal, with 80% above the pelvic brim. Those with angles below 50⁰ are likely to lead to clinical windsucking and associated complications.[1]
All breeds of horse can be affected but those with poor perineal muscling are at greater risk. The same applies to horses in poor body condition. Conformation often deteriorates with age.
Multiparous mares are more likely to suffer from the condition due to the stretching and trauma/scar related changes to the tissues.
A small proportion of horses affected are due to traumatic injury, most commonly caused by parturition due to positioning or posture of the foal at delivery.
Pathogenesis
When the vulvar commissure is below the pelvic brim, often due to poor body condition and lack of fat\muscle around the hindquarters, the vulval lips often slope anteriorly and/or lie partially open with a poor seal and thus air enters. The negative pressure within the reproductive tract then aids movement of the air into the vestibule, vagina and eventually cervix and uterus. This often makes a wind-sucking sound. A different, expulsory sound is often generated during movement, as the air is expelled under force.
Faeces can also enter and contaminate a vulva that is sloped anteriorly in a similar way. This is an important source of infection which can then ascend the tract all the way to the uterus where it may prevent or terminate a pregnancy.
Clinical Signs
Chronic pneumovagina causes vaginal flatus, erythema of the vaginal mucosa and air within the tract which is palpable on rectal examination and visible upon ultrasound examination.
Ascending infection if left unchecked can lead to placentitis which is an important cause of abortion in the horse. Commonly implicated organisms include Streptococcus zooepidemicus , Escherichia coli , Klebsiella pneumoniae , Pseudomonas aeruginosa , Staphylococcus aureus , Rhodococcus equi , and Actinobacillus equuli.
Abortion may be the first sign in a mare that has not been previously examined or had a history of reproductive problems.
Diagnosis
Clinical signs are sufficient to diagnose pneumovagina.
Vulvae can be physically assessed in terms of position, slope and seal quality, which aids in determination of risk. The Caslick index can be calculated by multiplying length of the vulva by angle of declination and values below 100 are favourable[1]. Procedures can then be instigated to lower the risk to a developing pregnancy as discussed below in treatment.
Examination of aborted foetuses will confirm presence of placentitis.
Many affected mares will have a history of subfertility, infertility or failed pregnancies.
Treatment
There is little point or justification for treatment of uterine/vaginal infection and inflammation if the vulvar conformation is not corrected as recurrence is otherwise inevitable.
Caslick’s operation or vulvoplasty of often the first line of treatment, closing the vulvar commissure partially to prevent contamination and air entry. The procedure is performed as soon as ovulation and breeding have been confirmed and sutures must be removed 5-10 days prior to parturition.
Pouret’s operation is a more invasive procedure which separates the reproductive tract from the caudal gastrointestinal tract and is usually reserved for very severe cases or where the Caslick’s has been unsuccessful.
Intrauterine or systemic antibiotics and anti-inflammatory therapy are also usually indicated for any existing infection/inflammation and post-operative care.
Control
Mares with poor vulvar conformation should not be bred from as there is a hereditary component to abnormalities.
The operations listed above can be used prophylactically in mares that have a history of infections/abortions/infertility.
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References
Lavoie, J-P., Hinchcliff, K. W (2008) Blackwell’s Five-Minute Veterinary Consult: Equine 2nd ed. Wiley-Blackwell, Oxford, pp 607 and 824-825.
Merck Veterinary Manual, Vulvitis and Vaginitis in Large Animals, accessed online 24/07/2011 at http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/111900.htm