PHILADELPHIA (AP) _ Many zoos across the country have agreed to begin tracking the West Nile virus, which is blamed for the deaths of at least three birds at The Philadelphia Zoo in the past month.
A flamingo, a pelican and a rare Humboldt penguin have succumbed to West Nile at the zoo since late August, and the virus is suspected in the death of a second Humboldt penguin. The warm-water penguins, whose numbers have dwindled to about 10,000, are believed to be the first endangered species to succumb to West Nile.
Fearing the virus will spread, a coalition of zoos, veterinarians and health officials have completed a plan to monitor it at zoos.
``We don't know what percentage of animals that are infected get sick and which sick ones die,'' said Dominic Travis, a veterinary epidemiologist at Lincoln Park Zoo in Chicago, who is leading the monitoring. ``Are the rest of the penguins all immune now? We just don't know. That's a huge reason why we're putting this plan into place.''
The only other zoo believed to have lost birds to West Nile is the Bronx Zoo in New York, where more than 20 birds died from the virus when it was first detected in 1999. But zoo officials fear the disease could spread easily through mosquitos, which carry the virus to animals and humans.
``One of the main challenges is that while our veterinarians and keepers certainly focus on prevention of any kind of disease, there's no way to prevent this entirely,'' said Jane Ballentine, spokeswoman for The American Zoo and Aquarium Association, an industry group with about 165 zoo members.
Under the pilot program _ details of which are expected to be released in the next several weeks _ more zoos will begin checking dead birds for West Nile. The program's second phase will involve zoos conducting blood tests on live birds.
Since the virus was discovered in the United States, West Nile has surfaced in 20 states _ mostly in the Northeast _ and scientists say it may reach Central America and California by early next year. Tennessee health officials said Monday that nine dead blue jays in Shelby County apparently had the virus, marking the first time it was identified in the state.
This year, 15 human cases including one death have been confirmed by the Centers for Disease Control.
People infected with West Nile virus suffer from flu-like symptoms. Zoo and health officials stressed that people shouldn't fear visiting zoos, because they're no more likely to be bitten by a virus-carrying mosquito at a zoo than they are in their own back yard.
Birds seem to be the most severely affected by the virus. A vaccine is currently being tested on birds but its effectiveness isn't yet known, said Bob McLean, director of the U.S. Geological Service's National Wildlife Center.
Meanwhile, some zoos with the room are keeping their animals indoors from dusk to dawn _ prime mosquito time _ and others are putting mosquito larvae-eating fish in their ponds, installing netting and using animal-friendly insecticides.