Pandemic prevention schemes threaten diversity, experts warn

Fear of a bird flu pandemic is threatening the survival of many rare avian species—and could ultimately put people in developing countries at greater risk of disease, experts say. The deadly H5N1 bird flu virus has struck at least 84% of known avian species. In a bid to forestall human infections, governments have ordered culls of millions of both healthy and infected birds. Depleting the numbers of species cuts down on the genetic diversity of bird populations, putting future generations—and people—at risk, experts say. If all birds had a similar genetic make-up, a particular viral strain might be able to wipe out an entire species, notes S. Reuben Shanthikumar, a veterinarian and former epidemiologist with the Food and Agriculture Organization. "This is certainly going to cause lack of animal protein and malnutrition and death of people, especially children, because it is the cheapest animal protein in many developing countries," he says. When virulent strains of bird flu are detected in a region, officials generally slaughter every bird within a designated radius, turning lakes into shooting ranges. In April 2004, for instance, several poultry flocks in Fraser Valley, British Columbia, tested positive for the H7N3 bird flu virus. Only about 7% of the 19 million birds in the region tested positive, but the Canadian Food Inspection Agency ordered all the birds killed. The valley provided at least 75% of British Columbia's poultry. The practice may be destructive both economically and ecologically, but it is still the best way to contain the virus, some experts argue. Vaccines for birds can stop the spread of the disease if a region is equipped with proper surveillance and security techniques, but is often not practical, particularly in developing countries. "How are you going to vaccinate 30 million chickens?" asks Edward Holmes, a biologist at Penn State University. Although H5N1 has only recently begun to dominate headlines, breeders have battled other bird flu strains for decades. Less virulent strains strike birds every year. To defend their flocks, poultry breeders are upping security measures, such as roofs over the pens. Others are dispersing their birds to several different regions to minimize loss should any given area become infected. The H5N1 strain is unusually potent and has killed more than 100 people since 1997. But in the documented human cases, the infection resulted from direct contact with birds. For an avian flu virus to be able to spread between people, it must first genetically evolve through a series of human-specific mutations. Most strains cannot bind to human tissue, and those that can are often doused by the immune system. To prevent a bird virus from adapting to humans, culling poultry is a reasonable strategy, says Holmes. "But you can't purge a virus from nature," he says. "If it's wild birds that don't come in contact with humans that you're culling, that's a different story." "Source":[ http://www.nature.com/nm/journal/v12/n6/full/nm0606-598a.html]

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