Test to better identify bird flu vaccination

In a project led by the University of Adelaide, researchers have developed a test that can distinguish between birds that have been vaccinated against the H5N1 strain of avian influenza virus (bird flu) with those that have been naturally infected. Writing in the journal PLOS One, the team said their work is a significant step in the fight against this often fatal strain of flu.

The strain is a cause of concern because of its possible transmission to humans and the threat of a pandemic if it mutates to a form that can be easily passed from bird to human, then human to human. It is already widespread in the poultry populations of South-East Asia, particularly Indonesia and Vietnam.

Project leader Dr Farhid Hemmatzadeh, from the University of Adelaide’s School of Animal and Veterinary Sciences, said outbreaks of the strain in birds are largely being controlled by vaccination, which also limits human exposure to the virus.

“But the inability of distinguishing between vaccinated and naturally infected birds has been a major challenge,” he stated. “It has prevented tracking the virus which can still circulate in vaccinated birds and may mutate to new strains under what’s called vaccination pressure.”

The vaccine is made from bird flu virus which has been killed but still promotes the production of antibodies protecting the bird against the live virus. The antibodies prevent the replication of the virus in the bird, but in some cases the virus mutates in a vaccinated bird and can still replicate - even with the existing high level of antibodies to the vaccines.

“These birds that have been vaccinated but still have live naturally infected H5N1 virus in their systems are the main source of emerging strains of the virus - and these new strains may be even more dangerous to birds or humans,” Dr Hemmatzadeh said.

The new DIVA test (differentiation of infected from vaccinated animals) uses a viral protein called Matrix protein 2 that reacts differently with blood serum from vaccinated or infected animals. Dr Hemmatzadeh said the test will enable researchers to identify vaccinated birds with live virus and prevent the escape of any mutant strains, which is “essential if we want to prevent pandemics developing from this virus and eventually eradicate this disease”.

The research collaboration, which includes the University of Melbourne, CSIRO and Indonesian organisations, is currently carrying out large surveillance programs in poultry farms across Indonesia. The work is funded by the Australian Centre for International Agricultural Research (ACIAR).

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