January 13, 2011

Genetically Modified Chickens Stop Bird Flu Virus

British scientists have successfully developed chickens that do not transmit bird flu infections, which could inevitably reduce the risk of deadly avian flu epidemics in humans.

Scientists from Cambridge and Edinburgh universities report that although the chickens they genetically modified (GM) still fell ill to H5N1 bird flu and died, they did not transmit the virus to other chickens they came into contact with.

"Preventing virus transmission in chickens should reduce the economic impact of the disease and reduce the risk posed to people," said Laurence Tiley, of Cambridge's department of veterinary medicine, one of the lead researchers on the study.

According to the world animal health organization OIE, H5N1 bird flu has been circulating in Asia and the Middle East, with occasional outbreaks in Europe, since 2003.  It has also killed or forced the destruction of hundreds of millions of birds.

The World Health Organization (WHO) has documented 516 cases of the deadly infection in people since 2003 and the virus has killed 306 of them.

Experts say the danger is that the virus will evolve into a form that people can easily catch and pass to one another, which causes the transmission rate to soar.  This would produce a pandemic in which millions of people would be endangered of death.

In Southeast Asia, China and parts of Africa, the H5N1 virus is already a major economic and food security issue, and it also poses a constant threat of being transmitted to humans.

South Korea said this week that it was raising its bird flu alert level after detecting H5N1 bird flu at poultry farms.

Helen Sang from the Roslin Institute at Edinburgh University, who worked with Tiley, told a conference that the GM chickens could offer a way to improve economic and food security in parts of the world where bird flu is a major threat, but said using them would probably add slightly to farming costs.

"Countries like China are interested in the possibility of genetic modification to protect their poultry stocks and people," she said. "It will inevitably be more expensive because you'd have to use the products of breeding companies to stock the producers."

Although large poultry producers could benefit from this early type of GM chicken, smaller "backyard" farmers still need to wait until scientists create birds that can be bred on small farms. 

"That would be a means of ensuring that the birds these small farmers bred themselves still carried the protective transgene," Tiley said.

The researchers introduced a new gene into their chickens that manufactures a small "decoy" molecule that mimics an important control element of the bird flu virus.

The replication machinery of the virus is tricked into recognizing the decoy molecule instead of the viral genes and this interferes with the virus' replication cycle.

The researchers infected 10 of them and 10 normal chicks with H5N1 bird flu after producing the modified chickens. 

The GM chickens became sick with the virus, but they did not transmit the infection on to other chickens kept in the same pen with them.  The study was published in Science.

The researchers said they now plan to work on trying to make chickens that are fully resistant to bird flu rather than just blocking bird-to-bird transmission.

"The genetic modification we describe is a significant first step along the path to developing chickens that are completely resistant to avian flu," Tiley said.


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