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Equine herpesvirus abortion


Equine Herpes Virus Type 1 (EHV-1) is the most important viral cause of abortion in horses. The virus is also the cause of respiratory disease (Equine rhinopneumonitis) and equine herpes virus encephalomyelitis (neurologic EHV-1)

EHV-1 is important to the equine industry, as it typically infects a wide range of cells and can potentially cause severe systemic illness. It has been proposed that there are two different variants of EHV-1: neuropathogenic and abortigenic. While the neuropathogenic strain of EHV-1 is considered exotic to Australia, the abortigenic strain is endemic in certain areas.

EHV-1 abortions usually occur in the last trimester of gestation, although they may occur earlier. Infected mares are typically asymptomatic although some can be pyrexic before aborting. Rarely, live foals are born with clinical signs of weakness and respiratory distress before death. An abortion storm involving several late gestation mares occurs infrequently due to the availability of rapid, sensitive and specific diagnostic tests for management of disease, and widespread vaccination.

Diagnosis and tests available


Diagnosis is based on clinical history, histopathology and virology.

Tests available


Sample(s) required

Days of the week test is conducted

Turnaround time1

Equine herpes virus – Type 1 PCR

Fresh tissue

According to demand

2-3 days

Equine herpes virus – Type 1 VNT

Clotted blood (red top tube)

Batch tested on Thursday

1-2 weeks

Histopathology examination

Fixed tissue or aborted foetus

Monday – Friday

Up to 5 days

1 Turnaround times are provided as a guide only. For specific information about your submission please contact Customer Service.

Specimen requirements

Aborted foetus

  • Whole, if possible
    • Submit chilled (not frozen) in leak proof bag

Blood (without anti-coagulant)

  • 10 mL of blood from mare collected into a plain red top tube
    • Submit chilled

Fixed tissue

  • Liver, lung and placenta
    • Submit fixed in neutral buffered formalin at a 10:1 ratio of formalin: tissue

Fresh tissue

  • Liver, lung, spleen, thymus and placenta
    • Submit chilled


  • Fees for tests undertaken to confirm or exclude a diagnosis of EHV-1 abortion are paid by NSW Department of Primary Industries. Extra testing to establish an alternative diagnosis is at submitters’ expense.
  • The EHV-1 PCR provides a definitive diagnosis of EHV-1 abortion. The virus neutralisation test (VNT) detects antibodies to EHV-1, but will also detect antibodies to EHV-4 (Equine rhinopneumonitis). A greater than four-fold increase in titre between acute and convalescent samples collected 3 weeks apart confirms recent infection (Acute samples should ideally be collected within the first 3-4 days of observable disease)