New avian flu vaccine for poultry developed
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Even if the protection is not as high as claimed, the results are impressive
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IN WHAT proves to be a significant step in developing a vaccine for poultry in the event of a bird flu outbreak, an Auburn University veterinary professor in collaboration with researchers at Vaxin Inc. of Birmingham has developed the first in ovo, or egg-injected vaccine.
Bird flu has again struck Vietnam in the recent weeks. No human casualty has been reported though.
Principle proven
According to Auburn University press release, the researchers inserted a gene from a low pathogenic avian flu virus strain (H5N9) into a non-replicating human virus, a Vaxin proprietary technology, which was then injected into developing chicken embryos still in the egg.
"We have proven the principle, which is the major step in leading to commercially produced vaccine that could be vital to the poultry industry," Dr. Haroldo Toro said.
"When an outbreak occurs, we would determine the strain and quickly create a vaccine within three months specifically for it." Dr. Haroldo Toro, whose research is in press in the scientific journal Vaccine, says it would provide 100 percent protection once an outbreak's strain is determined.
Even if the protection offered is not as high as the researcher claims, the results obtained are nevertheless impressive.
When protection induced by the vaccine was tested against two highly pathogenic avian flu viruses, a Vietnam H5N1 strain and a Mexican H5N2 strain, the results showed 68 percent and 100 percent protection, respectively.
Explaining the difference in protection to the two strains, Dr. Toro said: "These strains have slightly different genetic make ups which account for the different percentages in protection.
Our results indicate that we can provide effective protection against any strain after incorporating the gene of the field strain into our vaccine construct." The disease has decimated poultry populations in Asia in recent years.
Toro says United States health officials are continuously monitoring both chicken flocks and migratory birds that might bring new, highly pathogenic strains of the disease and infect poultry flocks, possibly killing between 90 percent to 100 percent in affected areas.
The current policy of health officials during an outbreak of highly pathogenic avian flu is mass culling and disposal of infected birds, and strict biosecurity measures.
Mass vaccination programs around the perimeter region would help to reduce the risk of further dissemination of the field virus to neighboring areas. Because this vaccine also allows easy differentiation between naturally infected birds and vaccinated birds, this new vaccine could also be used to prevent outbreaks of disease in case of immediate risk from a known strain affecting, for example, neighboring countries.
"We can vaccinate lots of birds in a quick, cost- and labor-saving manner which otherwise would not be possible," Toro said.
Sour point
Mass production of vaccine at a short notice has been a sour point. But the researcher feels he a solution for that as the vaccine he had developed is produced through cell culture, which will make it possible to easily make enough vaccine for thousands of birds.
He says this procedure is much easier than producing inactivated, or killed, vaccines, which require replicating the live avian influenza virus in egg embryos and individual delivery by injection. In addition, naturally infected chickens cannot be differentiated from those vaccinated if the strain used for vaccination is the same as the one acting in the field.
Easy to administer
Currently available recombinant vaccines using fowl pox vectors injected into the chicken have been shown to be less effective in birds pre-exposed to the vector.
Pre-exposure to the vector used in this novel vaccine is extremely unlikely in chicken populations. "Both of the current methods are difficult and labour intensive, and are too time consuming, when time is critical," he said.
"The in-egg vaccine is easy to produce, easy to administer and very effective. The vaccine would, in turn, reduce the risk for human exposure to avian influenza."
Even though the risk to people is low, there have been confirmed cases among humans reported since 1997, primarily in Asia as a result of contact with infected chicken, ducks and turkeys. — Our Bureau
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