Hendra Virus Watch

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A suspected case of Hendra virus infection in a horse was reported this fall from the far north coast of New South Wales in Australia, which is approximately 30 kilometers from the border with Queensland province, where the previous cases had occurred.

The Australian Deputy Chief Veterinary Officer has issued a caution to veterinarians working with sick horses showing symptoms that are consistent with Hendra virus infection.

Hendra virus infection in horses first appeared in Australia in 1994 where it caused the death of 13 horses and a trainer and sickening a stable hand, who recovered. Another outbreak the same year caused the death of two horses and their owner, who had participated in postmortem examinations. Single-horse cases were also identified in 1999, 2004 and June 2006.

An extensive wildlife survey in Australia found the large fruit bat (also known as flying foxes) is the reservoir of the virus, with almost 50% of bats tested having antibodies against the virus. Bats are asymptomatic, but shed the virus in their urine and reproductive tract. Infection is believed to occur when horses are exposed to bat urine or placental/uterine fluids when the bats give birth. It has been suggested that ticks may serve as a link between horses and bats. Horses also shed the virus in their urine and saliva.

Experts believe this virus has been in existence in the bat population for quite some time. It has now appeared as a ”new” disease in horses and humans as a result of natural bat habitats shrinking, forcing bats to move in closer contact to populated areas, and by humans and domestic animals encroaching into the remaining natural habitats of the bats.

The virus causes flu-like symptoms in people, pulmonary edema in horses, and can also cause severe neurological symptoms. Deaths may occur in as little as two to three days.

The Hendra virus infection of humans and horses has only been reported in a limited, subtropical area of Australia to date. Since the bat host species does not exist in this part of the world, the likelihood of this particular virus becoming easily established in the Northern hemisphere appears to be remote.

However, viruses are extremely adaptable, and a closely related virus, the Nipah virus, which has caused similar disease in pigs and humans in Malaysia, has also been found in smaller, insect-eating bats, such as those common in this part of the world.

There is no need to live in fear of these exotic diseases, but owners and veterinarians need to be aware of their existence. Horses with neurological disease should always been examined by a veterinarian and every attempt made to identify the cause. You should always be careful about contact with bodily fluids from horses with neurological disease until the cause is known. Remember, rabies can infect horses, too.