FieldDxHendra virus infectionClinical signs, differential diagnosis, treatment and prevention in horses.
Overview
A rare but frequently fatal viral respiratory disease of horses in Australia, transmissible to people. Hendra virus, a paramyxovirus carried by Pteropus fruit bats; horses are infected via contact with bat body fluids/excretions or by inhaling contaminated droplets.
Clinical signs
- Interstitial pneumonia.
Predisposing factors
- Residence in or travel to endemic areas of eastern Australia (Queensland and New South Wales); the disease has not been identified outside Australia.
- Close contact with Pteropus fruit bats (flying foxes), the natural reservoir host; infection occurs by oral or nasal exposure to bat urine, saliva, birthing fluids or fetal tissues.
- Grazing, feed bins or water troughs positioned under trees in which flying foxes roost or feed.
- Seasonality — most cases occur in the Australian winter/spring flying-fox birthing and nutritional-stress period.
Look-alikes to rule out
Equine Infectious Anemia (EIA) Equine Infectious Anemia (EIA / Swamp Fever)
Treatment
- There is no effective or specific antiviral treatment for infected animals; case fatality is approximately 75%.
- Supportive care only (fluid therapy, anti-inflammatories, oxygen) and this is rarely successful.
- Hendra virus infection is a notifiable disease — suspect cases must be reported immediately to the state or national animal health authority.
- Suspect horses must be isolated in situ (move other animals away rather than moving the sick horse) and handled only with full personal protective equipment (P2/N95 respirator, eye protection, impervious gown, gloves, boots).
- Because of the high zoonotic risk and near-uniform fatality, euthanasia of confirmed cases is the recommended course
Prevention
1. Vaccination is the single most effective preventive measure: Equivac HeV, a subunit (soluble G glycoprotein) vaccine, is registered for horses in Australia. Horses must be microchipped and vaccination details are entered on the HeV Vaccine National Registry. 2. Remove feed and water containers from beneath trees that attract flying foxes
Source
A Textbook of the Diseases of Cattle, Horses, Sheep, Pigs and Goat by ELSEVIER (Page 996) 108. Cols D, G, H added from: Merck Veterinary Manual, "Hendra Virus Infection in Horses", https://www.merckvetmanual.com/respiratory-system/respiratory-diseases-of-horses/hendra-virus-infection-in-horses and "Equine Morbillivirus Pneumonia (Hendra Virus Infection)", https://www.merckvetmanual.com/horse-owners/infectious-diseases-of-horses/equine-morbillivirus-pneumonia-or-hendra-virus-infection
MSD Veterinary Manual — Hendra Virus Infection in Horses (accessed 2026-08-11)
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