Equine placentitis is subtle in its onset, often causing the death of its victim—the unborn foal—before veterinarians can detect and treat it. Equipping veterinarians to identify these cases of placental infection early could help them prevent abortions, lost time on the breeding calendar, and the general heartbreak that can come with losing a foal.
A research team recently looked at whether two plasma estrogen concentrations could be potential diagnostic markers for early ascending placentitis. Barry A. Ball, DVM, PhD, Dipl ACT, presented the team’s findings at the 2013 American Association of Equine Practitioners’ Convention, held Dec. 7-11 in Nashville, Tenn.
The two estrogens they evaluated—estrone sulfate and 17β-estradiol sulfate—naturally circulate at high levels in pregnant mares with and without experimentally induced placentitis, so the researchers sought to determine if these hormones' concentrations could be used to detect infection. The team checked the mares' hormone levels at Day 0 (before experimental infection in the test group) and then daily for six days.
The found that estrone sulfate levels did not differ between the groups. However, 17β-estradiol sulfate levels dropped significantly within one day of inoculation in the mares with placentitis.
“It is important to note that the study we described deals only with experimentally induced placentitis and abortion in mares," Ball said. "We have yet to examine changes in estrogens in spontaneous clinically occurring cases of placentitis. The interval of estrogen values reported represents the average period of time between inoculation and subsequent pregnancy loss, which is the only period available to us for study.” In other words, in natural cases the onset of infection and resulting abortion might occur differently.
Though the researchers believe that estrogens will prove to be a useful indicator of problem pregnancies in the future, researchers need to verify which of the several hormones of the mare will be most relevant for detecting placentitis in clinical studies of horses with naturally occurring infection.
Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.