The national Centers for Disease Control and Prevention has enlisted zoos and aquariums across the country in the battle against West Nile virus. Two years after it was first reported in New York City in 1999, migratory birds have carried the potentially fatal flavivirus as far as Louisiana and Iowa.
Under the CDC-funded pilot program initiated in September, participating zoos and aquariums will actively monitor their outdoor bird and mammal collections for signs of West Nile infection, alerting the local public health department when the virus is confirmed. The information is also compiled in a central database that will be analyzed next year to provide the public health and veterinary professions a more complete picture of the virus.
So far this year, West Nile fever has been diagnosed in 25 people, and a Georgia woman is the only reported fatality, the CDC said in October. Infections have been confirmed in more than 4,000 crows and birds from 23 states, with 11 states reporting infections in some 100 horses.
Substantial resources have been allocated to tracking West Nile virus in human and animal populations, and attempting to limit its proliferation. But the workload is overwhelming, causing many state diagnostic laboratories to limit their testing to only crows. Their high susceptibility to the virus makes crows initial indicators of viral activity in an area. Much of the national West Nile surveillance system depends on public reporting of sick or dead crows and other birds.
What the zoo and aquarium project offers is a more active form of surveillance. Staff who are vigilant about detecting emerging diseases in the collection closely monitor animals that could potentially contract West Nile virus. Aquariums are included in the plan because some contain collections of outdoor birds. These highly controlled environments, along with their metropolitan locale, make zoos "perfect sentinels" for tracking the virus, according to veterinary epidemiologist Dr. Dominic Travis of the Lincoln Park Zoo in Chicago. Dr. Travis is overseeing the national database portion of the project, which is intended to yield new information about the virus, such as trends in certain animal species.
"We expect that as West Nile hits an area that zoos will be ideal places to either pick it up first, or if not, to verify when that area became positive," he said.
He and Dr. Tracey McNamara, head of the pathology department of the Wildlife Conservation Society headquartered at the Bronx Zoo in New York, are project coordinators. Dr. Amy Glaser with the New York State Diagnostic Laboratory at the Cornell University College of Veterinary Medicine is overseeing the sample-testing portion.
In June they met at Lincoln Park Zoo with a host of government public health, agriculture, and wildlife officials, including representatives with the American Zoo and Aquarium Association and American Association of Zoo Veterinarians, to discuss the feasibility of incorporating West Nile virus surveillance data from zoos into the national public health database. Afterward, the CDC agreed to allocate $50,000 for the project for one year.
The project strives to foster new ties between the human and animal health professions. Most zoos and aquariums do not have a relationship with their local health department, Dr. McNamara pointed out. The project's reporting framework is designed to build these communication lines, and by doing so, give veterinarians a more active role in protecting public health.
The schism between the health professions was made evident during the summer of 1999 when West Nile virus appeared for the first time in the Western Hemisphere. In and around New York City, a rash of mysterious illness in people, with some deaths, coincided with massive bird die-off. Federal and state health officials initially ruled the cause as St. Louis encephalitis, caused by a rare flavivirus that affects humans but does not kill birds. Dr. McNamara, who was investigating the bird deaths, helped make the connection that West Nile virus was the cause of the human and bird outbreaks.
Since then, there is a growing recognition of veterinarians' role in safeguarding public health, Dr. McNamara said, adding that her mission has been to bridge the gap between the veterinary and human health sectors. A General Accounting Office report to Congress following the outbreak in the Northeast stated that links between public and animal health agencies are becoming more important. "In these times of emerging infections and zoonotic disease hazards, that's probably in everyone's best interest," she said.
The standardized West Nile surveillance plan, drafted with support from the American Zoo and Aquarium Association and American Association of Zoo Veterinarians, was sent to 201 AZA-accredited institutions. Ill or dead outdoor birds and mammals will have blood and tissue samples taken. In addition, sick or dead wildlife discovered on zoo grounds or brought in for treatment will be tested. Samples are sent to the Cornell diagnostic laboratory where, at no charge to the submitting institution, they are tested for the virus. Testing measures include virus isolation, reverse transcriptase-polymerase chain reaction, and serology. Zoos have also been asked to submit banked blood samples of collection animals for testing at Cornell.
At press time in October, between 100 and 200 samples had been submitted, according to Dr. Glaser. And since the geographic distribution of West Nile virus has "exploded" this year, the laboratory is accepting samples from any zoo, regardless of AZA accreditation, she added.
Within a few days, the laboratory reports its findings to the submitting institution, which informs the local health department about positive and negative test results. Reporting negatives establishes when West Nile virus became active in a given area. If a sample tests positive, the health care community there implements measures to protect the public from infection while curbing mosquito activity.
"The reason they want it reported at the local level is because that's where response happens," Dr. Travis explained. "They would need to be the first ones to know."
A key component of the project is privacy. Zoos and aquariums worry they will see a decline in ticket sales if it is publicized that West Nile virus is found on their grounds. To pacify these concerns, reporting is confidential to shield participating institutions from potentially negative press. "There's been a tendency to not think about the [harmful] effects of the [public relations] on these institutions who are run on their gate receipts a lot of time," Dr. Travis said. "The agreement is that you'll treat animal medical records with the same confidentiality that you treat people's medical records."
For the most part, the procedures are not burdensome for the zoological institutions, Dr. Travis said, although fish and wildlife permits are required by law for testing regulated wildlife found on zoo grounds or brought for treatment. There is a push to get the project permitted nationally, but it will take some time. Other project goals include developing more rapid diagnostic tests that detect West Nile virus, as well as improving tests that work across multiple species. Surviving animals will be studied to determine the long-term effects of infection, which is difficult to do in free-ranging wildlife. It is hoped that additional diagnostic laboratories will participate, leading to a standardized zoo surveillance program for emerging zoonotic infectious diseases that will complement the existing public health network.
"I hope that this project is the first step in working toward one health," Dr. McNamara said. "We're all part of an ecosystem. You can't just look at one species in isolation and expect to have all the answers."