Causes of equine abortion: infectious and noninfectious

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Equine abortion can be caused by noninfectious and infectious factors.

Noninfectious Causes:

* Twining: This results in abortion between 8 and 9 months of gestation and is preceded by premature lactation. The cause of death is placental insufficiency.

* Umbilical Cord Torsion: This can cause localized swelling or hemorrhage, subcutaneous edema, and a swollen soft liver. Microscopic mineralization of the placental vessels is also a sign.

* Mare Reproductive Loss Syndrome (MRLS): This is caused by the Eastern Tent Caterpillar and leads to fibrinous pericarditis and unilateral uveitis. Mares with MRLS may experience colic, fever, and a purulent vulvular discharge.

* Fescue Grass Toxicosis: The ingestion of fescue grass infected with the endophyte Neotyphodium coenophialum can cause prolonged gestation, agalactia, edema, and premature placental separation. Abortion from this cause typically happens in the last two months of gestation.

Infectious Causes:

* Equine Rhinopneumonitis (EHV-1 and EHV-4): Abortion occurs after 7 months of gestation. The fetus may have subcutaneous edema, jaundice, an enlarged liver with yellow-white lesions, and an increased volume of thoracic fluid. Prevention is possible through vaccination of the mare at 5, 7, and 9 months of gestation.

* Equine Viral Arteritis (EVA): Abortion can happen 6 to 29 days after a mare shows clinical signs of EVA. This can cause arteritis in the fetal myocardium or placenta.

* Bacterial Abortion: This is characterized by premature udder development, increased uteroplacental thickening at the cervical star, and a mucopurulent vaginal discharge. Common bacteria isolated include E. coli, P. aeruginosa, and K. pneumoniae.

* Leptospira: Most abortions from Leptospira occur between 6 and 9 months of gestation. The placenta may be thick, heavy, edematous, and hemorrhagic.

* Nocardioform Placentitis: This can result in abortion, stillbirths, or weak foals born at term. The fetus is often underdeveloped.

* Potomac Horse Fever: This is a mid to late-term abortion caused by Ehrlichia risticii. A presumptive diagnosis can be made by identifying fetal colitis.

* Mycotic Placentitis: A fetus aborted in late gestation may be fresh with signs of growth retardation. A pale, enlarged liver or dermatitis may be present.

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