Hendra Virus Update

Once hendra virus is suspected the horse is quarantined, and to obtain the samples for testing or to carry out testing, personal protective equipment--including gloves, special masks, disposable coveralls, and booties--is essential.

By C.J. (Kate) Savage BVSc(Hons), MS, PhD, Dipl. ACVIM, Oceanic WEVA delegate

In recent years, a deadly disease--hendra virus--has been making waves in the Australian equine industry. Hendra virus is a rare but nearly always fatal infection of horses; however, it is of grave concern because it is a lethal zoonotic agent (meaning it is transmissible from horses to humans) that can also prove deadly for people.

Hendra virus was named after the suburb in Queensland where it was first isolated in 1994. The virus was formerly known as "equine morbillivirus" and was first recognized in as the cause of an outbreak of acute respiratory disease in horses. Infected horses display clinical signs of breathing difficulties and/or neurologic signs, frequently with high fevers. The chain of transmission appears to be flying fox (a type of fruit bat of the genus Pteropus) to horse, and then horse to human.

Veterinarians have recognized hendra virus infection and disease in horses in two Australian states: Queensland and New South Wales--which are located in the warm northeastern region of the country. Since 1994 more than 60 horses have been affected, while seven people have been affected, several of whom have died.

Although hendra virus spread to humans is very rare, the consequences of infection are so serious that horse people must consider the possibility and take biosecurity precautions when dealing with potentially affected horses. There is risk for caretakers nursing the sick horse (i.e., before hendra virus is suspected or confirmed), examining and collecting clinical samples (for example, veterinarians performing a physical examination and/or endoscopy of the throat and windpipe), or for people involved in testing body fluids/secretions for the virus in the laboratory. Once hendra virus is suspected the horse is quarantined, and to obtain the samples for testing or to carry out testing, personal protective equipment--including gloves, special masks, disposable coveralls, and booties--is essential. Those involved in testing or caring for a possible hendra horse must have a heightened awareness of personal hygiene (i.e., washing hands thoroughly and regularly) to prevent disease transmission.

In the laboratory, hendra virus samples are only worked upon using the greatest biosecurity level. The known human infections have occurred after contact with the secretions and bodily fluids (such as blood, pus, mucus, and urine) of infected horses at the time the horse has been terminally ill or during necropsy examination. There have been no reports of bat-to-human or human-to-human transmission.

Deborah Middleton, BVetSc (Hons), MVetSc, PhD, Dipl. VCS, a senior veterinarian at the Commonwealth Scientific and Industrial Research Organization, and her co-workers have been developing a horse vaccine they hope can be used as early as 2014. Immunization of horses is exciting because it might protect horses that are exposed to infected flying foxes. Even if an immunized horse becomes infected, the vaccine could markedly decrease viral replication so that it helps stop hendra virus from spreading.

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