Wednesday, July 05, 2006
After West Nile virus: what will it do to the birds and beasts of North America?
The alligators at Clabrook Farm were under the weather last fall. Some seemed depressed, others were wobbly, and a few crawled in circles. Within a few days of first showing such symptoms, alligators at the farm near Christmas, Fla., sank into neurological meltdown and died. During September and October, the farm lost about 300 of the 9,000 gators that it was raising for meat and hide.
In mid-October, one of the farm's baffled owners took three of his sick hatchlings, to reptile veterinarian Elliott R. Jacobson of the University of Florida in Gainesville. Recognizing that they had some kind of brain malady, Jacobson ordered tests for West Nile virus and several other pathogens.
No North American alligator had ever been diagnosed with the infection, but then again North American alligators hadn't had much of a chance to catch it. The virus was reported in the Western Hemisphere for the first time in August 1999 in New York City, where it caused a cluster of human cases of flulike symptoms, some of which turned into fatal brain inflammation. The first West Nile cases confirmed in Florida were a horse's and crow's demise reported in July 2001.
Moreover, people pick up the disease from the bite of an infected mosquito, so the notoriously tough-skinned alligators didn't seem an obvious candidate for that infection route.
Yet when Jacobson tested the animals' blood and organs, West Nile virus was evident. Although scientists are still debating how the North American alligator catches the disease, the species now appears on the official roster kept by the National Wildlife Health Center in Madison, Wis., that lists the more than 200 "species found positive for West Nile virus."
This month, biologists report that the disease has reached birds in the Caribbean. A bananaquit in Jamaica has turned up with West Nile-virus antibodies in its blood, says Peter P. Marra of the Smithsonian Environmental Research Center in Edgewater, Md. This bird doesn't migrate, so it must have caught the virus locally.
Because New World wildlife has not had to contend with the virus before, defenses aren't in place. Some species are experiencing what appears to be an animal version of the epidemics of smallpox and other new diseases that devastated native peoples when Europeans arrived.
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