Placentitis in Mares: Causes, Symptoms & Treatment
Placentitis in mares refers to the inflammation of the placenta and is a significant cause of abortion, premature birth, stillbirth, or neonatal sepsis in broodmares. It is estimated to affect 3 to 5% of pregnancies in Thoroughbred mares.
Mares at higher risk include older mares, those with multiple previous pregnancies, mares with poor perineal conformation, and Thoroughbreds. Understanding its causes, treatment options, and preventive measures is essential to protecting both mare and foal for horse owners.
Understanding Placentitis in Mares
Placentitis is the inflammation of the placenta, often caused by bacteria like Streptococcus or E. coli, and sometimes by fungi. It can also result from viruses from Equine Herpesvirus (EHV-1 and EHV-4).
Early signs may include premature udder development or vulvar discharge. Timely detection and treatment, typically with antibiotics and supportive care, can help preserve the pregnancy, protect the foal, and reduce economic losses.
Types of Placentitis
Placentitis in pregnant mares can occur in several forms:
Ascending Placentitis: The most common type, caused by bacteria entering through the vagina and cervix, usually affects the cranial (front) part of the placenta. This form of placentitis is most common in mid-gestation, between 6 and 9 months.
Focal Mucoid Placentitis: It is characterized by localized thick, mucous-like inflammation in a specific area of the placenta. It is primarily caused by gram-positive bacteria and may occur during late gestation.
Diffuse Placentitis: This type of placentitis occurs when the bacteria or fungi spread to the placenta through the bloodstream. It can be associated with systemic infections like Leptospirosis.
Multifocal Placentitis: This variant is characterized by the presence of multiple separate inflamed areas scattered across the placenta. It is often caused by bacterial or fungal infections.
Symptoms of Placentitis in Mares
The common symptoms of placentitis in mares are
Premature udder development (6-12 weeks before the mare's due date)
Vulvar discharge
Premature lactation
Reduced fetal movement
Restlessness or behavioral changes
Placental separation
Foaling with a "red bag" delivery
Occasionally, no visible symptoms until complications arise
Risk Factors
Certain factors make mares more susceptible to placentitis. These include:
Older mares
Mares with multiple previous pregnancies
Mares with cervical injuries, such as lacerations or scar tissue on the cervix, can allow pathogens to enter the uterus.
Mares with poor conformation of the vulva or perineum are more susceptible to ascending infections.
Mares with a history of chronic uterine infections
Mares with placentitis are at increased risk for retained fetal membranes
Placentitis is primarily caused by infections, but several other factors can increase the risk:
Bacterial Infections: The most common cause, often involving Streptococcus equi subsp. zooepidemicus, Escherichia coli, and other opportunistic bacteria, typically leading to ascending placentitis.
Fungal Infections: Less common but can cause severe inflammation, sometimes resulting in abortion.
Viral Infections: Rare, but certain viruses may trigger placental inflammation.
Other Contributing Factors:
Previous reproductive tract infections
Poor perineal conformation
Older age or multiple prior pregnancies
Physical stress, injury, or trauma during pregnancy
Environmental factors, such as poor hygiene or contaminated housing
How Placentitis in Mares is Diagnosed
Placentitis is diagnosed through a combination of ultrasonography, bloodwork, and clinical signs of placentitis in mares:
Clinical Examination
Observation of early signs such as premature udder development, vulvar discharge, or changes in behavior.
Physical examination of the reproductive tract by a veterinarian to detect inflammation or abnormalities.
Ultrasound Imaging
Transrectal or transabdominal ultrasound can detect thickening of the placenta, separation from the uterine wall, or abnormal fluid accumulation.
Useful for monitoring progression and response to treatment.
Laboratory Tests
Blood tests to detect inflammation or infection markers in the mare.
Measuring serum amyloid A (SAA) levels can help identify inflammation.
Vaginal or cervical swabs for bacterial culture to identify the specific pathogen.
Amniotic fluid or placental tissue analysis in some cases.
Importance of Veterinary Care
Veterinary care is essential for detecting, managing, and treating placentitis effectively. A veterinarian can take necessary steps to prevent pregnancy loss:
Identify early signs through clinical examination and diagnostic tests.
Prescribe appropriate treatments such as antibiotics, anti-inflammatories, or supportive therapies.
Monitor the mare and placenta via ultrasound to track treatment progress.
Advise on management practices to prevent recurrence in future pregnancies.
Treatment Options for Placentitis in Mares
Treating placentitis in mares involves a combination of therapies aimed at reducing inflammation, combating infection, and supporting the pregnancy.
Anti-inflammatory Medications: Use of anti-inflammatory meds can reduce inflammation and inhibit prostaglandin production, which may otherwise induce premature labor.
Progesterone Supplementation: Supplementing with progesterone supports pregnancy maintenance and helps prevent premature uterine contractions.
Supportive Care: Providing stall rest, ensuring proper nutrition, and maintaining hydration are essential for the mare's overall health and the developing foal.
Monitoring: Regular veterinary check-ups, including ultrasound examinations, are crucial to assess the progression of placental health and fetal development.
Note: Consult a veterinarian and refrain from self-medicating your mares without professional supervision.
Discover more about horse breeding practices to prevent reproductive complications in your mares.
How to Prevent Placentitis in Mares
Here's how to prevent placentitis in mares:
Maintain Hygiene: Keep stalls, paddocks, and breeding areas clean to minimize bacterial and fungal exposure.
Regular Veterinary Care: Routine reproductive exams and monitoring help detect early issues before they escalate.
Manage Reproductive Health: Treat any vaginal or uterine infections promptly; avoid breeding mares with ongoing infections.
Assess Vulvar Conformation: Check for poor perineal and vulvar conformation. A Caslick's procedure may be recommended to close the vulva partially, reducing fecal contamination risk.
Vaccinate: Vaccinate mares pre-breeding and at specific stages of pregnancy against pathogens like E. coli and EHV-1, as directed by your veterinarian.
Optimize Nutrition: Provide balanced diets with adequate vitamins and minerals to support immune function and overall health.
Monitor High-Risk Mares: Older mares, those with multiple prior pregnancies, or poor perineal conformation should be closely observed, especially during late pregnancy.
Stress Reduction: Minimize physical and environmental stressors during gestation.
What to Do When Placentitis Happens
Placentitis is a manageable health issue, and its primary treatment includes a combination of medications to fight the infection, reduce inflammation, and support the pregnancy.
Immediate Steps for Mare Owners
Isolate the affected mare to reduce the risk of spreading infection.
Contact a veterinarian immediately for proper diagnosis and treatment.
Look for signs like premature udder development, milk leakage, or vaginal discharge.
Administer antibodies and anti-inflammatories to the mare as per the vet's instructions.
Emotional and Practical Considerations
Manage stress for caretakers, as dealing with placentitis can be emotionally challenging.
Prepare for potential late-term abortion or other complications to ensure timely intervention if needed.
Future Care
Monitor subsequent pregnancies closely, especially in mares with a history of placentitis.
Adjust breeding plans based on the mare's reproductive history and veterinary guidance.
For foals born to a mare with placentitis, monitor for infection, ensure colostrum intake within 12–24 hours, and have a new-foal exam (including a SNAP test) within 18–24 hours of birth.
Prognosis and Long-Term Effects of Placentitis in Mares
Prognosis:
The outcome depends on the type of placentitis, the gestational stage at detection, and how quickly treatment begins.
Early diagnosis and prompt, appropriate treatment improve the chances of carrying the foal to term.
In severe cases, abortion or stillbirth may occur despite intervention.
Long-Term Effects:
Mares that have experienced placentitis may have an increased risk in future pregnancies.
Reproductive performance may be affected, particularly if there was significant placental damage.
With careful monitoring and veterinary management, many mares can successfully carry subsequent pregnancies.
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Conclusion
Placentitis in mares is a treatable condition, and with timely intervention, caregivers and horse owners can prevent the economic losses associated with pregnancy loss. The key is early detection of warning signs, implementing preventive measures promptly, and closely monitoring the mare throughout gestation to ensure the best possible outcome for both mare and foal.
FAQs
What is placentitis in mares?
Placentitis is the inflammation of the placenta, often caused by bacterial, fungal, or viral infections, and can lead to abortion, premature birth, or neonatal illness.
How is placentitis diagnosed in pregnant mares?
Diagnosis involves clinical examination, ultrasound imaging to assess placental health, and laboratory tests such as blood work or bacterial cultures.
What are the treatment options for placentitis in mares?
Treatment includes antibiotics, anti-inflammatory medications, progesterone supplementation, supportive care, and regular monitoring under veterinary supervision.
Can placentitis cause abortion in mares?
Yes, placentitis is a significant cause of late-term abortion or stillbirth if not detected and treated early.
How can placentitis in mares be prevented?
Preventive measures include maintaining hygiene, vaccinating mares, assessing vulvar conformation (Caslick's procedure if needed), managing reproductive health, optimizing nutrition, and closely monitoring high-risk mares.
