[ASC-media] CSIRO: Aussie ravens ruled out as West Nile virus indicators

Rebecca.Eveleigh at csiro.au Rebecca.Eveleigh at csiro.au
Mon Jan 14 23:25:02 CET 2008


15 January 2008

Ref 08/04

Aussie ravens ruled out as West Nile virus indicators 

Scientists at CSIRO's Australian Animal Health Laboratory (AAHL) in
Geelong, Victoria have found that birds are unlikely to be used as part
of an 'early warning' system designed to alert health authorities to the
presence of the deadly West Nile virus in Australia.

The AAHL research was part of an Australian Biosecurity Cooperative
Research Centre (AB-CRC) for Emerging Infectious Disease program which
focuses on finding effective methods for detecting West Nile virus in
Australia. 

While the zoonotic disease, West Nile virus, is not present in
Australia, it has been reported for many years in eastern Mediterranean
and southern European countries. It was first detected in North America
in 1999 - emerging in New York City and rapidly spreading to all 48 US
states, Canada and Mexico. It's estimated more than 200,000 people in
the US have been infected with the virus.

The virus is transmitted to humans by infected mosquitoes and the
reservoir host is a wide range of birds. The majority of infected humans
display only mild flu-like symptoms or no symptoms at all. However, some
individuals may suffer severe illness due to encephalitis which may
result in death. 

Research leader, CSIRO's Dr John Bingham, says in the US dead-bird
surveillance is considered the most sensitive early detection system for
the virus, with dead birds, mainly crows, appearing weeks, even months,
before human cases. 

The study aimed to determine if the early detection methods of dead-bird
pick ups was valid for the New York strain of West Nile virus in an
Australian context.

"We couldn't assume that West Nile virus would be highly lethal to
Australian corvid species - ravens and crows - as has been observed in
the US.  Our bird species are different and we have a virus similar to
West Nile - Kunjin virus - here already. Although it has not been
reported to cause disease, Kunjin virus may confer immunity in birds to
the highly pathogenic West Nile virus," Dr Bingham says.

The project investigated what happens when a bird species common to
Australian urban areas - the Little Raven (Corvus mellori) - was exposed
to West Nile or Kunjin virus. All work with the infectious viruses was
conducted within the secure biocontainment facilities at AAHL.
 
Dr Bingham says the study found Little Ravens were relatively resistant
to the New York strain of West Nile virus and Kunjin virus.

"Unlike American corvids who suffer high mortality rates when exposed to
West Nile virus, the Australian ravens exposed to the virus showed only
mild clinical signs and all infected birds recovered. This means
Australia's Little Raven could not be used as an early warning sentinel,
indicating the presence of West Nile virus in Australia," he said.

The study also provided information which can be used to further
validate AAHL's diagnostic tests for the virus. 
 
Researchers at Queensland Health are undertaking further work to help
find an alternative 'early warning' system for West Nile virus in
Australia, based on examination of mosquitoes.

Image available at:
http://www.scienceimage.csiro.au/mediarelease/mr08-04.html   


Further Information:
	
John Bingham, CSIRO Livestock Industries
03 5227 5008 john.bingham at csiro.au  

Media Assistance:	

Emma Wilkins, CSIRO Livestock Industries
03 5227 5123 emma.wilkins at csiro.au  

www.csiro.au

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Beck Eveleigh
Media Assistant
CSIRO Media Liaison
6276 6451
0409 395 010
 



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