Necking our cranes
Not bad for less than four years work.
In the future, the virus could appear almost anywhere in the hemisphere, says USGS biologist Paul Slota. "There's an awful lot of [bird] migration to Alaska, and to Central and South America, the Caribbean, and there's a lot of concern that it will follow bird populations north and south."
The peril of bird extinction is particularly acute in Hawaii, where the native birds have already been decimated by mosquitoes carrying bird pox and bird malaria.
Epidemics and other ecological changes are most threatening to rare species like the Hawaiian honeycreepers or the California condor since small populations are more susceptible to any problem.
Of particular concern is the whooping crane, a majestic wading bird that almost went extinct in the 1940s. Although whoopers have come back -- about 400 now live in captivity or in the wild -- they remain highly endangered. Fortunately, while West Nile has infected 158 bird species, no whoopers are known to have gotten sick from it, says veterinarian Barry Hartup, who minds the health of dozens of cranes from around the world living at the International Crane Foundation.
It's a slightly different story with the more numerous sandhill cranes, he adds. In 2002, seven chicks of the Mississippi subspecies died at the Audubon Center for Research of Endangered Species. The center is in New Orleans, where the virus is active.
Tests of West Nile vaccine on greater sandhill cranes, a non-endangered subspecies, at the Patuxent Wildlife Research Center and the National Wildlife Health Center were inconclusive. Neither the control nor the experimental animals got sick after being experimentally infected, but the vaccinated birds "developed higher antibody levels and had shorter periods of virus in the bloodstream," says Hartup.
The virulence -- infectivity and mortality -- of West Nile has been fairly stable since it arrived, says Komar. And while it's true that mutations can help diseases lose their viciousness, he says, "It can work the other way around as well. They occasionally evolve into being more deadly, and this may be one of those instances. ... In this case, we are probably dealing with a mutation that leads to greater virulence, allows the virus to spread more quickly."
City of New York.
A flying start
Like the Spanish galleons of old, the jet an equal-opportunity transporter, hauling people and pathogens alike and creating opportunities for other emerging infections.
But if the future of West Nile is not predictable, history does offer a sobering caution. "West Nile has spread a lot in the last four years, and it will probably continue to spread," says Komar. "It has infected a large number of species, and will probably continue to infect a large number; the affected species list will probably continue to grow. But whatever happens from here is anybody's guess."
Nothing sick about our bibliography.
©2003, University of Wisconsin, Board of Regents.