Light Shed On Mystery Horse Disease

CSIRO (Commonwealth Scientific and Industrial Research Organization—Australia's largest scientific research organization) Animal Health scientists have discovered more about the mysterious Hendra disease that killed two humans and fifteen horses in Queensland in two outbreaks in 1994-5.

Scientist Dr Mark Williamson says research at the CSIRO's Australian Animal Health Laboratory (AAHL) in Geelong has shown that while the Hendra virus is not highly contagious, it is often deadly if an infection occurs.

Formerly known as the equine morbillivirus, the Hendra virus has been shown to infect humans, horses, cats and guinea pigs. Fruit bats (also called flying foxes) are thought to be the natural 'host' of the virus.

The research findings are published in the Australian Veterinary Journal today (December 14).

"Basic research and understanding of this virus will be critical if there are ever further outbreaks of the disease. But perhaps of greater importance, is that the basic understanding gained through the research can be applied to other viruses," Dr Williamson says.

The CSIRO research demonstrates that horses can be infected by eating material contaminated with the virus, and that transmission from cat urine to horses can occur. Horses, cats and guinea pigs excrete the virus in their urine. Most importantly, the research also shows the virus was not carried on the breath of horses.

The Hendra virus produces both lung and brain disease, consistent with related viruses such as canine distemper and measles.

Dr Williamson also noted that during the four-year research program into the Hendra virus, two previously unknown diseases also associated with bats have been identified in Australia.

The Australian bat lyssavirus was identified in 1996 after samples from a sick bat were sent to AAHL for testing for Hendra virus. Tests in fact showed that the disease was caused by a close relative of rabies, which occurs overseas.

Two people are known to have died from the illness.

A Rockhampton (Qld) bat carer died from the illness in 1996. A second fatality occurred yesterday, with the death of a woman from Mackay (Qld) who was bitten by an infected bat two years ago.

The other virus, known as the Menangle virus was first isolated in 1997 by NSW Agriculture after pig illness and miscarriage in a NSW piggery, and influenza like symptoms occurred in piggery workers. The Menangle virus is also carried by fruit bats.

"The number of 'new' viruses discovered in Australia this decade means that this type of basic research is even more important. It ensures that we maintain our skills in dealing with newly emerging diseases," Dr Williamson says.

AAHL scientists first identified the Hendra virus after tissue samples were rushed from Queensland during an outbreak of the mystery disease in Hendra in1994, in which one human and thirteen horses died. The scientists showed the disease was not caused by an exotic (foreign) disease, but was in fact a new virus that had not previously been identified.

One person and two horses died in a later outbreak in Mackay in 1994-95. There have been no further outbreaks of the disease since that time.

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