In 1994, a deadly new virus threatened to stop Australia’s premier horse race - the Melbourne Cup. This virus is now known as Hendra virus.
Introduction
In September 1994, a prominent Queensland horse trainer Mr Vic Rail, his stablehand, and most of his horses fell ill to a sudden and mysterious illness.
Within several days, the trainer and 14 horses were dead. As the Queensland Department of Primary Industries (QDPI) collected specimens from affected race horses and submitted them for testing at CSIRO’s Australian Animal Health Laboratory (AAHL) in Geelong, Victoria, newspapers ran with headlines like 'Death virus cancels races, threatens Cup'.
AAHL's diagnostic team isolated and identified what proved to be a new virus that had not been reported anywhere else in the world.
Researchers initially named it equine morbillivirus but further genetic analysis showed that the most appropriate classification of the virus was as a new genus within the Paramyxoviridae family.
The name Hendra is now used, after the name of the Brisbane suburb in which the outbreak occurred.
The strength of AAHL's capabilities was clearly demonstrated by the manner in which the infectious agent was isolated, the disease reproduced in horses and the virus eventually identified using electron microscopy and gene sequence analysis.
With the cause of the disease outbreak known, AAHL researchers developed diagnostic tests. QDPI, Queensland Health and AAHL tested more than 2 500 horse samples and 150 human samples, not finding any new cases.
Further cases (current at September 2009)
In the last 15 years, seven people have been confirmed to have been infected with Hendra virus, and four have died as a result of the disease. In addition to the initial case in 1994, a farmer from Mackay died in 1995 and two Queensland vets passed away in separate incidents in 2008 and 2009.
There have also been 13 clusters of Hendra virus infection recorded in horses since the virus was first identified.
As a national facility, AAHL is required to provide diagnosis of emergency animal diseases, which includes:
- index case confirmation
- national emergency response capability
- use of accredited and validated tests.
This has meant the facility has been actively involved in each recorded Hendra virus incident.
Research findings
Unlike other Paramyxoviridae viruses which tend to be host-specific, Hendra can infect more than one animal species.
Scientists believe fruit bats are the natural ‘host’ of the virus, meaning the virus is carried by bats but has little effect on them. However, when transmitted to humans and horses, the virus can be lethal.
AAHL researchers were awarded the CSIRO Chairman's Medal in recognition of their work in identifying Hendra virus.
AAHL research shows that horses, cats and guinea pigs can excrete virus in their urine. The virus isn't carried on the breath of horses. This helps to explain why Hendra virus isn’t highly contagious.
The means by which Hendra virus infected the horses at Hendra and Mackay isn't known. Infected bat urine, an aborted bat foetus or reproductive fluids could have been involved.
In 1995 the AAHL research team was awarded the CSIRO Chairman's Medal in recognition of its work in identifying the new virus.
Continuing research
Research on Hendra virus and Nipah virus, a closely related virus first discovered in 1999, continues at AAHL.
A major research breakthrough occurred in 2005 when an international team, including AAHL researchers, identified the part of the cell membrane to which both Hendra and Nipah virus attach in order to enter and infect the cell
This discovery accelerated research in many different areas, including the development of improved diagnosis, vaccine, and anti-viral drug targets.
Recently, the group at AAHL in collaboration with US scientists evaluated a potential human vaccine to provide protection against both Nipah and Hendra virus.
The results of this research, published in July this year, represents significant progress towards the development of a human vaccine to be used in the event of a another natural outbreak, a laboratory accident, or deliberate misuse.
McEachern JA, Bingham J, Crameri G, Green DJ, Hancock TJ, Middleton D, Feng YR, Broder CC, Wang LF, Bossart KN. 2008. A recombinant subunit vaccine formulation protects against lethal Nipah virus challenge in cats. Vaccine. 26(31):3842-52. [external link]
Further research is planned to develop improved high throughput screening tests to evaluate Nipah antivirals, and three different therapeutic approaches to combat Hendra virus including:
- a human/animal vaccine
- antibody therapy
- small molecule drugs.
Scientists at AAHL are studying bat ecology and the bat immune system to determine how viruses, such as Hendra, maintain themselves in bats and how they ‘spill over’ into humans and other animals.
Research to understand more about zoonotic diseases is also being undertaken, with a focus on the interaction of bats and viruses and identifying and characterising new and emerging infectious agents.
Biocontainment
CSIRO scientists who undertake research with Hendra virus and Nipah virus must work at Biosafety Level 4 (BSL4) - the highest biosecurity level. This requires scientists to wear fully encapsulated suits with their own air supply.
AAHL provides a unique resource for Australia and its capacity to work with deadly Biosafety Level 4 disease agents is arguably the best in the world.
Watch the ABC Catalyst episode on Hendra virus [external link].
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