Hendra Virus

A very topical issue at the moment is that of Hendra Virus. With the recent outbreaks in Northern Queensland Hendra is foremost in many horse owners minds.

Hendra Virus is an emerging disease that is carried by flying foxes that has the potential to cause fatal disease in horses and humans. The first case was reported 15 years ago in the Brisbane suburb of Hendra and there have been a total of 12 incidents since involving 42 horses and 7 people. All clinical cases so far have occurred on the east coast between Cairns and Murwillumbah.

Hendra virus attacks blood vessels all over the body. This explains the wide range of symptoms seen in horses suffering from the disease. Horses with Hendra usually exhibit a rapid onset of illness with an equally rapid deterioration in health. They have a fever (often over 40 degrees celcius) and a rapid heart rate. As seen in the recent outbreaks, horses may exhibit respiratory and/or neurological signs.

Flying foxes are the natural host of this disease and Hendra Virus has been present within these bats for hundreds or thousands of years. It appears that fruit bats and flying foxes are the only species of bat affected. Bats do not get sick with Hendra, and as many as 20-50% of bats tested showed evidence of previous exposure. Very few of these bats are actively excreting virus which helps explain why spillover into horses remains a rare event.

So the question remains….how do bats transmit the virus to horses? The answer to this unfortunately is still unknown. Current research suggests that horses are ingesting bat bodily fluids such as urine, faeces or placental fluids. This may happen when horses are fed, watered or seek shelter under or adjacent to native flowering trees and fruit trees where bats are feeding. Bats may also feed directly on horse feed, particularly if horses are being fed bat attracting foods such as carrots, apples or molasses.

The answer as to how people get Hendra virus from horses is much simpler. Virus is shed in the bodily fluids of infected horses and direct contact is required between these fluids and people for transmission to occur. Luckily for those of us who deal with horses on a daily basis, Hendra appears to be a difficult disease to contract. There is no evidence of human to human transmission but that does not mean it can’t happen.

Protecting yourself and your horses from Hendra Virus involves keeping your horses away from flowering and fruiting trees particularly during the bats breeding season of June to October. Avoid feeding bat attracting foods and follow simple hygiene procedures – the virus is easy to kill. Wash your hands with soap and water each time you handle a horse. Most of all be vigilant. If your horse is sick, particularly in late winter or early spring, take precautions with hygiene and call a veterinarian.