Web Zap*Germs Archive

March 16, 2006

Rinderpest Eradication Strategy Suggested for Bird Flu

Today's WSJ highlights a discussion going on within the public-health community regarding how to eradicate avian flu from animal hosts living in areas with high infection rates dubbed "viral reservoirs." They're looking at the strategy being used to combat rinderpest, a cattle disease, in Africa. Rinderpest has been almost wiped out (no cases reported in the past five years!) due to a strategy of vaccinating heavily in viral-reservoir areas, rather than attempting to vaccinate every single at-risk animal.
For decades, veterinary authorities embraced one basic approach to attacking rinderpest: mass vaccination. That helped rid many countries of the disease. But Dr. [Peter] Roeder says the approach sometimes failed in places where there simply weren't enough veterinarians or vaccine supplies to guarantee thorough coverage, leaving pockets of unprotected animals that could harbor the virus. In Ethiopia, for instance, veterinary officers repeatedly trekked through the desert in an attempt to inoculate every cow in the country. But the virus remained firmly entrenched in the east African nation.

"Why try to vaccinate the whole of Ethiopia?" Dr. Roeder says. "You could never do that."

The key to rinderpest's defeat, he says, lay in being selective. It was better to leave certain areas altogether unprotected, he says, if that allowed a blitzkrieg attack with all available resources on stubborn strongholds of the disease -- so-called viral reservoirs. These reservoirs were often in remote areas, far from veterinary services and vaccines, with a high density of animals in which the virus thrived.

The idea has begun to resonate with some bird-flu experts. China last year announced an ambitious plan to vaccinate its billions of birds. But last month, a group of nearly 30 scientists from around the world argued in a paper published in the Proceedings of the National Academy of Sciences that southern China in particular has been a breeding ground for avian influenza viruses for at least a decade, allowing the virus to fester and spread from there. Eliminating the virus at its source, in Guangdong province, they argue, could go a long way to eliminating the disease.

"A lot of people don't understand it," Dr. Roeder says. "They just think it's vaccination, vaccination, vaccination, but they don't realize that you can vaccinate for 30 years and still have the disease right under your nose." But he adds, "unless you understand this, you don't have a hope in hell with a disease-control program. And that's the same with avian influenza."


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