Hunting carriers of a deadly virus

July 30, 1999

A $600 million hermetically sealed centre is leading the fight against diseases threatening Australian farming and the population

There is no taking work home at weekends for Alex Hyatt or the 100 or so other scientists at Australia's Animal Health Laboratory (AAHL) at Geelong, near Melbourne.

Rather, the Commonwealth and Scientific Industrial Research Organisation scientists have to leave everything - including their underwear - in their specially built offices, which are contained within a one-metre thick concrete casing at an isolated site on the outskirts of the town.

Dr Hyatt and his colleagues are at the forefront of Australia's drive to protect the country's livestock - which constitutes a major export earner for Australia - from endemic and exotic (foreign) diseases. They are responsible for identifying and researching new and emerging diseases, and for developing vaccines and programmes of disease eradication.

To undertake this work, scientists at the laboratories have to work with live viruses; viruses which, if they escaped, could wreak havoc among livestock, wildlife and even human populations. Hence all work is undertaken with the strictest security.

Just to go to work scientists have to remove all their home-clothes before passing through special airlocks and putting on overalls and undergarments that are washed and prepared in the centre's own laundry.

Each of the rooms in the complex is held at progressively lower air pressures with the most dangerous viruses - those able to infect and cause illness in humans (zoonotics) and for which there is currently no vaccine or cure - kept at the lowest pressure. Any leak or breach of security within the complex would see air gushing into an area from outside, as opposed to the virus escaping. To work with any of the zoonotic viruses, scientists have also to don special high-pressure space suits with their own oxygen supply.

Leaving the complex is no mean feat either. A minimum three-minute shower is needed before scientists can leave and even then they cannot mix with farm animals for another seven days. Taking home paperwork, or even an apple from the canteen (which is, incidentally, the only room with windows), is strictly prohibited. All correspondence must be faxed or emailed, all apples eaten on site. The air in the centre is filtered and cleaned on the premises, as is the waste.

"I work in a concrete box within a box," says Hyatt, of the Aus$600 million centre where he has worked for the past 15 years as an electron microscopist. "It tends to feel a little sterile and isolated. But you adjust. When a new disease turns up here, it tends to be something of a very serious nature - something major affecting the economy or health. Because you are removed from the field, it becomes like solving a mystery. When you find what causes it, that's exciting. It's what keeps you going in the job."

Hyatt has recently had plenty to keep him excited. In the past five years alone, at least seven new animal diseases have emerged in Australia - at least two of which have proven fatal to humans.

First came hendra, a completely new virus not reported anywhere else in the world, which killed two humans and 15 horses in two separate outbreaks in Queensland in 1994. Another horse died of the same virus just five months ago. Scientists at AAHL isolated and identified the virus by sequencing viral genes. After genetic analysis of the entire virus, scientists believe its most appropriate classification is as a new genus within the Paramyxoviridae family, which includes measles and rinderpest.

Scientists now believe flying foxes (fruit bats) to be the natural host of the virus. Antibodies to hendra virus were found in four species of fruit bats collected in Queensland, with 25 per cent of bats surveyed displaying antibodies to the virus. It suggests fruit bats have, in the past, been exposed to the virus. Experiments at the lab have shown that, experimentally, horses can be infected with hendra by eating material contaminated with the virus and that transmission from cat urine to horses can occur.

During the research, a second previously unknown disease, also potentially fatal to humans and associated with bats, was identified. The Australian bat lyssavirus was isolated in 1996 after a sample from a sick bat was analysed at AAHL. Tests found a close relative of the rabies virus. Australia is free of classical rabies, but bat lyssavirus is known to have been responsible for at least two human deaths in the past two years.

More recently, thousands of pigs and more than 100 humans have perished in the Malaysian countryside since September from a previously unknown disease.

Until only a few months ago, the Malaysian government believed mosquitoes, the spreader of Japanese encephalitis, were to blame for the deaths. However, more recent studies have shown the disease is in fact a new virus, since named nipah, which is closely related to hendra. Early gene sequencing suggests it is only about 20 per cent different from hendra, the virus that scoured the Queensland horse industry.

Once again, scientists, including several from Australia, have been hunting the source of the virus. Suspicion has fallen again on flying foxes, which feed in the fruit trees adjacent to the Malaysian farms where the outbreak is thought to have started. The farms are carved into the edge of the forest. Several individual bats have already been found positive for antibodies to nipah virus, though this does not conclusively prove their role as the source of the virus.

"I think personally we will see more of these viruses over the next few years," says Hyatt. "In the early to mid 1990s, these viruses started to emerge in this country and overseas and they have not stopped yet. As man encroaches more into the areas he has not before farmed, and as agriculture changes its practices, we will see more and more diseases not described before."

He explains that human expansion into previously forested areas is bringing them into contact with flying foxes, for example, and thus with viruses to which we have previously not been exposed. Unknown diseases are the likely consequence.

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