Genetics make some chickens resistant to bird flu

Scientists, including one of Indian-origin, have discovered that the genes of some chickens make them almost completely resistant to a serious strain of bird flu, a finding that may help better understand the mechanisms of avian influenza transmission.
Influenza virus is the cause of influenza, or 'flu' - the contagious respiratory viral disease common in many birds and mammals.
The viruses circulating in wild birds and domesticated poultry may mutate into forms that are capable of infecting humans, and represent an emerging threat to human health as potential sources of the next flu pandemic.
This danger has led the World Health Organisation (WHO) to highlight effective control measures, as well as an in-depth assessment of factors surrounding the infection of host animals, as part of their research priorities.

"It is important for us to understand how different genetic lines of bird react to influenza viruses, so that we can begin to understand the spread of the disease," said Colin Butter from the University of Lincoln in the UK, who led the study.
"Until now we knew relatively little about how a bird's genetics can affect its reaction to flu virus but this new research, which for the first time shows that some poultry lines are genetically resistant to avian flu, represents a significant step forwards," Butter said.

"Our results are valuable in emphasising the important role a 'host' plays in the spread of avian flu, and also in highlighting a number factors relating to the chain of infection and control mechanisms which are affected by the route of infection," he added.

The researchers examined two different lines of chickens to determine whether genetics played a part in the susceptibility or resistance to infection.
They found that birds that carried the virus but were genetically resistant to the disease only shed the virus through their respiratory tract and for a limited period of time, whereas birds which were susceptible to the disease also shed virus in faeces and over a longer time.
The researchers discovered that this was the only relevant means of spreading the virus and that resistant birds were therefore completely unable to initiate or sustain a chain of infection.

Further results in the study suggest that this could be due to a genetic restriction within the animal which stops the virus spreading when inside the body.
"The findings of this study emphasise the importance of examining the intricate nature of the virus-host interactions and the potential role of the host genetic factors influencing the transmission dynamics and outcomes of important diseases such as avian flu," said Venugopal Nair, the Head of the Avian Viral Diseases programme at The Pirbright Institute.
The study was published in the journal Scientific Reports.