Chickens which cannot spread bird flu have been created by scientists at the Universities of Edinburgh and Cambridge.

Researchers have successfully developed genetically modified chickens which, while still capable of being infected with bird flu, do not pass the infection to non-modified chickens with which they are in contact.

In a study published in the journal Science, the researchers explain how the introduction of a small gene helps infected animals produce "decoy" molecules which confuse the replication cycle of the virus.

Professor Helen Sang from the University of Edinburgh's Roslin Institute said the research could also be applied to pigs to prevent the spread of swine flu.

She added that it could help protect food stocks by making "our production animals much healthier, our losses much less... providing the animal products the growing population of the world will need".