Update: Equine Herpesvirus-1

Tuesday, March 19, 2019

(Non-NY) Herpesvirus 1 abortion: A 14-year-old Quarter horse mare developed a precocious udder and aborted two days later. She was 9 months pregnant at the time. The mare had been vaccinated against EHV 1 at 5, 7 and 9 months of gestation. The veterinarian performed a field necropsy on the fetus and did an abortion work up, providing a complete set of fresh and fixed tissues from the fetus and placenta, as well as serum and EDTA whole blood from the mare.

Fluorescent antibody (FA) testing was positive for EHV 1 (rhinopneumonitis virus) on placenta, fetal lung, kidney and adrenal gland. EHV 1 PCR was a high positive on fetal lung and thymus. EHV 1 virus was grown from fetal tissue on viral isolation. Histologic description of the lung and thymus included intranuclear inclusion bodies, which is a hallmark of herpes virus. The mare's serum EHV 1 serum neutralization (antibody) titer was 384 at the time of abortion. EHV 1 abortions have been reported in well vaccinated herds of horses [1] and should be considered in the differential of any abortion.  Biosecurity measures should be instituted until a diagnosis is determined. A complete abortion work-up is important to determine the etiology of equine abortions.  


  1. Barrandeguy ME, Lascombes F, Llorente J, Houssay H, Fernandez F. High case‐rate Equine herpesvirus‐1 abortion outbreak in vaccinated polo mares in Argentina. Equine Veterinary Education. 2002 Jun;14(3):132-5.