Hendra Virus Has A Growing Family Tree

CSIRO Livestock Industries scientists Dr Linfa Wang and Dr Bryan Eaton have this week published a review paper in Infectious Disease Review, describing the long line of viruses from Hendra's viral family, Paramyxoviridae that have cropped up around the world since 1962.

Fifteen new paramyxoviruses have been discovered in the past forty years in animal hosts ranging from dolphins, seals, snakes, rats, bats, to horses and humans,

Dr Wang says CSIRO's Australian Animal Health Laboratory (AAHL) is now the only institute in the world holding a collection of all major newly discovered paramyxoviruses. He predicts the collection will grow over the next decade.

"It is almost inevitable that new viruses will be discovered. This is a family of viruses where it is clear there are many more members out there that we don't know about yet," he says.

"These new viruses are important, because some are causing threats to public health, livestock production and trade, and many may also pose a risk to wild animals where populations have already been reduced by environmental destruction or other factors.

"AAHL's collection of paramyxoviruses and further comparative research puts us in a strong position to help diagnose and respond to the next emerging paramyxovirus," Dr Wang says.

"The genomic characterization of these new viruses has significantly expanded our knowledge about paramyxovirus evolution. A new virus genus has been established based on our recent studies, and several other viruses are yet to be classified."

Retrospective analysis by the team has identified some intriguing patterns.

CSIRO scientists have now completed deciphering the genetic code of two viruses, one found in a Brazilian bat in 1979, and another that caused a brain disease in Mexican pigs in 1984. As the genetic analysis shows the two viruses are closely related, scientists believe the Mexican virus may have jumped to pigs from bats, as is believed to have happened with other newly emergent paramyxoviruses, Menangle virus in Australia in 1997, and the Nipah virus in Malaysia in 1999.

Four of the fifteen viruses that are under investigation have recently emerged in Australia, or were isolated in this country many years ago and have remained uncharacterised.

Mossman virus was first detected in Queensland in 1970, in a rat. Three years later, J virus was discovered, also in Queensland, in wild mice. Dr Bryan Eaton says the two paramyxoviruses are now being characterized to better understand where they sit in the viral family tree.

"Already it is clear that they are novel members of the growing paramyxovirus family. We also want to understand the disease-causing potential of the viruses," he says.

The other two paramyxoviruses that have emerged in Australia are Hendra virus, which killed two people and several horses in 1994, 1995 and 1999 in Queensland, and Menangle virus, which caused stillborn piglets in a New South Wales piggery. Two piggery workers suffered an influenza-like illness and were believed to have been infected with Menangle virus in 1997. Both Hendra virus and Menangle virus are believed to be carried by flying foxes, (fruit bats).

A group of Queensland-based researchers proved the link between bats and Hendra virus when they isolated the virus from the animals, confirming other evidence such as some bats being found with specific antibodies to the virus.

The relevant State authorities successfully contained outbreaks of the Hendra and Menangle viruses. The Nipah virus outbreak in Malaysia was also successfully brought under control.

The Executive Committee of the International Committee for the Taxonomy of Viruses has agreed to name the genus within the Paramyxoviridae family that contains the Hendra and Nipah viruses, Henipavirus.

Henipavirus becomes the fourth genus within the Paramyxovirinae subfamily of the Paramyxoviridae family. The other genera within the subfamily are Rubulavirus, Morbillivirus and Respirovirus.