An Introduction to Horse Care
by Dr. Giovanna Romano / dvm, dipl Ecar
Board Specialist at the European College of Animal Reproduction, in the Equine Subspecialty. Dr. Romano, one of the founding partners and owner in 1998, is deeply involved in breeding industry. As a doctor in veterinary medicine, she coordinates a staff o co-worker managing with particular attention the reproductive pathologies in mares and stallions. Co-author in many international publications on a new Assisted Foaling Technique and on the Embryo Transfer, and invited speaker in the Italian Equine Reproduction Conference, Dr. Romano is the Scientific Coordinator of the Centro Equino Arcadia: a unique spot in Northern Italy for students and new graduates training on the base of the EEU requirements.
Equine Placentitis Update
What’s the most common cause of late-term abortion in horses and remains challenging for veterinarians to diagnose and treat, despite ongoing research? If you said placentitis, you’re right. Placentitis—an inflammation of the placenta—is often caused by an ascending infection that enters the mare’s uterus through the cervix. placentitis is responsible for 10-40% of late-term abortions in mares; of those cases 60% are of the bacterial variety. Clinical signs of placentitis often develop late in the course of disease and are generally nonspecific. The most common clinical sign is premature udder development, and less commonly vulvar discharge. However, many cases simply present with late-term abortion or the birth of a sick or weak foal.
While early diagnosis would likely improve the chances of positive clinical outcomes, veterinarians are currently limited in their diagnostic options for placentitis.
Ultrasound Screening—Since the technique was introduced in 1997, ultrasound examination of the uterus and placenta has been the mainstay of placentitis diagnostics. Research indicates that the normal combined thickness of uterus and placenta (CTUP) for healthy mares less than 270 days of gestation is less than 7 millimeters (mm); mares ranging from 271 to 300 days of gestation should have a CTUP of less than 8 mm; mares between Days 301 and 330 should have a CTUP of less than 10 mm; and mares over 330 days should have a CTUP of less than 12 mm. Measurements above those normal ranges are clear indications of uterine pathology and suggestive of placentitis.
Frequent monitoring of mares with no known risk factors for placentitis represents a significant expense and may not be cost-effective or feasible.
Nonetheless, at this time, ultrasonographic examination of the combined thickness of the uterus and placenta represents the most sensitive and specific diagnostic and screening tool that can be recommended for valuable or high-risk patients.
Hormone Tests— researchers have also explored the efficacy of measuring serum progestagen to diagnose or screen for placentitis. In mares with compromised pregnancies, previous research has shown that serum progestagen levels will either elevate prematurely (all mares’ levels rise after 310 days of gestation) or drop severely, typically just before abortion.
Prematurely rising progestagens are indicative of chronic stress to the foal, of which placentitis is by far the most common; falling progestagens indicate fetal demise and are not specific. Elevated progestagen may occur at the same time as early thickening. Usually if progestagens are dropping quickly, treatment is too late.
SAA Tests—Finally, recent research that explored the use of inflammatory blood protein levels to identify inflammation within the body. Specifically, researchers tested one inflammatory protein’s (called serum amyloid A, or SAA) ability to identify mares with experimentally induced placentitis in late gestation. They found that mares’ serum SAA levels rose significantly 48-144 hours after experimental infection, while control mares’ SAA levels remained low, save for a short rise surrounding parturition.
These findings warrant further work in clinical cases of naturally occurring placentitis to determine whether SAA may be used as an inexpensive, sensitive screening tool for placental function, and whether it is influenced by confounding factors such as extra-uterine disease or obesity. SAA levels are not specific to placentitis—meaning any inflammation or infection within the body can cause those levels to rise—so veterinarians should interpret those results with caution.
Traditionally veterinarians have used a combination of antibiotics, anti-inflammatory drugs, immune-modulatory medications, and progestins to treat placentitis.
And recent research has been shedding light on which medications and treatment methods might be most effective in reaching therapeutic concentrations in allantoic fluid (fluid in the chorioallantois, which is the outer layer of the placenta where the placenta and maternal uterus touch and exchange nutrients); 83% of the mares in this research protocol delivered viable foals, compared with no viable foals being born in the control group. Unfortunately, those results haven’t been replicated in clinical practice since very important is the proper time of detection of the clinical signs which makes important the regular check of pregnancies in the last trimester.