Pathfinder
Editor, Senior Moderator
US farms hit by bird flu ? but a vaccine might make things worse
Updated 14:49 28 April 2015 by Debora MacKenzie
...
At the moment, an infected farm must kill all of its birds to stop H5N2. Poultry producers want a vaccine instead. Researchers at the US Department of Agriculture are starting tests, and Clifford says he is talking to vaccine companies.
But "vaccination will always be the last option for avian influenza," says Henry Wan of Mississippi State University, who discovered H5N1 in 1996. Widespread poultry vaccination in China, Indonesia and Egypt has not got rid of that strain.
On the contrary, vaccinated poultry spread the virus without getting sick, making its spread invisible. Vaccination has moreover driven the evolution of H5N1 as these viruses adapt to the vaccinated birds. China is now trapped, say researchers: it wants to give up expensive poultry vaccination, but if it did, ubiquitous, silent infections with H5N1 would decimate the unvaccinated birds.
Even if the US avoided this trap, vaccination would hurt its poultry exports, worth $3 billion a year. Tests cannot distinguish vaccinated from infected birds, so importers reject meat and eggs from countries that vaccinate their poultry.
Ruben Donis of the US Centers for Disease Control and Prevention calls relying on vaccines to control bird flu "unrealistic". It might be possible to use an H5N2 vaccine on some high-risk farms with careful monitoring for silent infections, he says. But "so far, there is no reason to believe that H5 could not be controlled through culling", plus sanitary precautions aimed at keeping environmental viruses out of henhouses.
...
http://www.newscientist.com/article...ine-might-make-things-worse.html#.VT-9lyFViko
Updated 14:49 28 April 2015 by Debora MacKenzie
...
At the moment, an infected farm must kill all of its birds to stop H5N2. Poultry producers want a vaccine instead. Researchers at the US Department of Agriculture are starting tests, and Clifford says he is talking to vaccine companies.
But "vaccination will always be the last option for avian influenza," says Henry Wan of Mississippi State University, who discovered H5N1 in 1996. Widespread poultry vaccination in China, Indonesia and Egypt has not got rid of that strain.
On the contrary, vaccinated poultry spread the virus without getting sick, making its spread invisible. Vaccination has moreover driven the evolution of H5N1 as these viruses adapt to the vaccinated birds. China is now trapped, say researchers: it wants to give up expensive poultry vaccination, but if it did, ubiquitous, silent infections with H5N1 would decimate the unvaccinated birds.
Even if the US avoided this trap, vaccination would hurt its poultry exports, worth $3 billion a year. Tests cannot distinguish vaccinated from infected birds, so importers reject meat and eggs from countries that vaccinate their poultry.
Ruben Donis of the US Centers for Disease Control and Prevention calls relying on vaccines to control bird flu "unrealistic". It might be possible to use an H5N2 vaccine on some high-risk farms with careful monitoring for silent infections, he says. But "so far, there is no reason to believe that H5 could not be controlled through culling", plus sanitary precautions aimed at keeping environmental viruses out of henhouses.
...
http://www.newscientist.com/article...ine-might-make-things-worse.html#.VT-9lyFViko