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Vaccines Protect Birds from Bird Flu, other Viruses

Posted on: Monday, 22 May 2006, 16:00 CDT

By Maggie Fox, Health and Science Correspondent

WASHINGTON (Reuters) - A bird flu vaccine piggybacked onto a widely used vaccine against another bird virus could be a quick and easy way to protect poultry against the H5N1 avian influenza virus, researchers said on Monday.

Two separate teams of researchers came up with a combination that is easy to make, protects chickens well and could be sprayed onto flocks.

Plus the vaccines are formulated in a way that answers the concerns that a bid flu virus could actually mask an outbreak, or could make trade in poultry products from vaccinated flocks more difficult, the researchers wrote in reports published in the Proceedings of the National Academy of Sciences.

"This is clearly only a chicken vaccine," cautioned Dr. Peter Palese of the Mount Sinai School of Medicine in New York, who worked on one of the vaccines.

That is because it is based on the widely used vaccine against Newcastle disease, another scourge of poultry but one which, unlike H5N1, does not affect people.

This is the vaccine's advantage, however, Palese said. Dozens of companies make Newcastle virus vaccine, which is easy to give to chickens.

"They send a guy into these closed houses with hundreds of thousands of chickens and just spray it," Palese said in a telephone interview. It's very cheap to administer. It costs a fraction of a cent per dose."

The H5N1 virus has accelerated its spread among birds, moving out of East Asia across the Asian continent and into most of Europe and many parts of Africa. Experts expect it will eventually become entrenched among birds globally.

It has killed or forced the slaughter of hundreds of millions of birds and occasionally infects people.

It has killed 123 people so far, all of whom have had contact of some sort with infected birds, but experts fear this virus has an especially good chance of mutating into a form that could pass easily from human to human, causing a pandemic.

CONTROLLING AT SOURCE

The best way to control it, experts also agree, is to contain it in birds. And other avian flu viruses can also ruin commercial flocks and can occasionally sicken humans, including the H7N7 and H9N2 strains.

Palese and colleagues grafted a piece of the H7N7 virus onto the Newcastle virus used in a commercial vaccine. It protected 90 percent of the chickens, they said.

Angela Roemer-Oberdoerfer and colleagues at the Friedrich Loeffler Institut at the Federal Research Institute for Animal Health in Riems, Germany made a similar vaccine using H5N1.

Theirs worked well, too, and the formulation overcame some of the objections to vaccinating chickens against avian influenza.

Some of the avian influenza vaccines for chickens that are now used allow the birds to spread the virus without appearing ill, and many countries will not import poultry products from vaccinated chickens.

In addition, when scientists test birds, it is impossible to tell if a chicken has antibodies against influenza because it was vaccinated or because it was infected.

This vaccine can easily be detected in a blood test and did not allow the birds to "shed," or transmit, the virus, Roemer-Oberdoerfer's team reported.

And they believe their approach could work in people.

Considering the current threat of pandemic H5N1, this approach should seriously be considered, they wrote.

Palese disagreed, saying current methods using other viruses are better.

"It theoretically is possible, but not realistic," he said.

People do not naturally get Newcastle disease, Palese noted. Human vaccines usually employ a virus that easily infect humans, to get a safe and effective immune system response.

Source: REUTERS

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