Equine Morbillivirus Pneumonia (or Hendra Virus Infection)

Equine morbillivirus pneumonia is a frequently fatal viral respiratory infection of horses caused by Hendra virus. Disease due to Hendra virus infection has only been reported in horses and people. There have been multiple outbreaks among people and horses in Australia since 1994. The virus is carried by specific species of fruit bats (flying foxes). Infection occurs by oral or nasal exposure.

Hendra virus does not appear to be highly contagious. Transmission between infected and uninfected horses occurs infrequently. Based on available field and laboratory data, infection of humans or animals appears to require direct contact with virus-infective secretions (nasal discharge), urine, or tissues.

In infected horses, signs include fever (up to 106°F [41°C]), poor appetite, lethargy, elevated respiratory and heart rates, difficulty breathing, pneumonia, and frothy clear to blood-tinged nasal discharge. Additional signs seen in some affected horses include bluish-colored or jaundiced mucous membranes, tissue swelling, and neurologic signs. As many as 60 to 70% of infected horses die of the disease. The course of the disease is short; death may occur within 1 to 3 days.

There is no specific antiviral treatment for this disease. Hendra virus is transmissible to humans. The infection has been fatal in a high percentage of the handful of human cases recorded so far, either from severe pneumonia or from inflammation of the brain. Direct contact with infectious respiratory secretions, urine, or tissues appears to be necessary for viral transmission. Equine veterinarians and horse owners are considered at risk. A commercial vaccine for use in horses is available on a limited basis. Horses must have a microchip to be vaccinated, and the information is entered into the HeV Vaccine National Registry in Australia.