For mares in which poor cervical tone is diagnosed, progesterone may be administered. Although the frequency of naturally occurring abortion due to PHF is unknown, Ehrlichia risticii , the organism causing PHF, has clearly been established as a cause of equine abortion. Classically PHF is known as a diarrheal disease. Fever, depression, anorexia, colic, and laminitis are other features seen in the horse. Following recovery from PHF, pregnant mares may abort.
Abortion is accompanied by placentitis and retained placenta in most cases.
There are three vaccines available for the prevention of PHF, however the effect of vaccination on the occurrence of abortion is unknown at this time. Typically you see discreet pale areas on the placenta. Treatment of the underlying cause may help the mare continue the pregnancy. Some advocate the use of progesterone. Premature lactation or udder development are consistent signs of placentitis.