Zoos are on the lookout for West Nile virus

As the mosquito-borne West Nile virus makes its way across the country, public health officials are on the lookout for signs of new outbreaks. These signs may appear not in hospital emergency rooms but in zoos.

Because keepers and caretakers watch their animals vigilantly -- and keep comprehensive medical records -- zoos provide a highly sensitive surveillance network for infections that cross species, such as the West Nile virus, which attacks birds, domestic animals and wildlife as well as humans.

“A lot of diseases start in animals,” says Dr. Dominic Travis, a veterinary epidemiologist with the Lincoln Park Zoo in Chicago and co-coordinator of the National Zoological West Nile Virus Surveillance Working Group. “If the animals become ill [with West Nile], we would be the first to know because we watch them so carefully.”

The connection wasn’t always so clear. During this country’s first West Nile outbreak in August 1999, health officials had no idea what was causing the sometimes fatal illness.

But Dr. Tracey McNamara, then a veterinary pathologist at the Bronx Zoo, soon suspected a connection to the huge number of dead crows she was finding on the grounds of New York’s Bronx and Queens zoos.

Autopsies revealed that the crows had bled from the brain and that their hearts were badly damaged -- virus symptoms similar to those affecting humans.

She helped to identify the culprit: the West Nile virus, which had never been found in the Western Hemisphere.

“One of the major challenges we faced with West Nile in 1999 was that there was no established means of communication between the veterinary and the public health world,” says McNamara, who is also a co-coordinator of the new surveillance network. “When you’re dealing with a disease that involves an entire ecosystem, it requires a lot of cooperation.”

Public health officials soon realized the importance of joining forces with the nation’s zoos to track the westward migration of the virus. The mosquito-borne virus hitchhikes across the country on birds; humans and animals become infected when they’re bitten by mosquitoes.

The zoo surveillance program, which is funded by the U.S. Centers for Disease Control and Prevention in Atlanta, started in 2001 with 35 zoos and aquariums (many aquariums have outdoor wildlife). It has since mushroomed into a nationwide network of more than 130 institutions, including wildlife sanctuaries and private veterinarians from New York to Alaska. The Los Angeles and San Diego zoos are among participants.

As part of the program, zoo workers take tissue samples from ill or dead outdoor zoo animals and dead wildlife found on zoo grounds. Test results are sent to local health agencies and to a database in Atlanta.

“Every little bit of information helps,” says Travis.

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Being vigilant in your backyard

The West Nile virus seems to have taken up permanent residence in the United States, health experts say.

Last year, more than 4,000 people in 39 states were sickened by the virus and 277 died. Although there was but one confirmed case in Los Angeles last year, more are expected this year. (The virus is dormant in the winter when mosquitoes are absent.)

Consumers can limit their exposure to mosquitoes that may carry the West Nile virus. Wearing protective clothing outdoors, including long-sleeved shirts and long pants, and using insect repellents can help. Because mosquitoes breed in even small amounts of water, it’s also advisable to eliminate sources of standing water.

Make sure gutters, pipes and other water sources drain away from your home. Don’t over-water your yard. Drain water that collects in pool and spa covers, flowerpots or barrels. Invert stored containers.