Zoos, by their very nature, are destined to be intimately involved with and knowledgable about the West Nile virus. This fact should not be viewed as a source of alarm or embarrassment, but rather of pride. As institutions, zoos have taken up the challenge presented by this new scourge with great expertise, ingenuity, determination, and candor. Judging from the experience of zoos that have already encountered West Nile, it’s clearly possible for parks to protect their captive animals and their guests, while at the same time becoming a valuable resource for enhancing public health through education and research. If you doubt it, simply ask Dr. Tracy McNamara, head of the pathology department at the Bronx Zoo for the past 17 years. The veterinary pathologist doesn’t mince her words. “It was only because someone cared enough about what was killing the flamingos at the Bronx Zoo that we know that this virus is in the Western Hemisphere,” she states flatly. She should know. She was the “someone” whose intuition and persistence led to the discovery that the disease had made its way to North America. Making the Connection In July of 1999, dead crows were discovered in large numbers in the New York City area. When a crow cadaver was discovered in the grounds of the zoo, there was understandable concern that whatever took the animal’s life might be transmitted to the captive animals in the park. McNamara performed a complete necropsy of the crow, scrutinizing its blood and tissues to look for signs of poisons, bacteria, or other disease-causing agents. “When I looked under the microscope, what I saw on the slides was highly suggestive of viral encephalitis,” she explains. Just a few weeks later, several of the zoo’s captive birds, including a flamingo, were found dead. McNamara’s examinations of those animals were consistent with the findings she made on the crows. There were any number of common causes that might account for the malady, but McNamara was puzzled by one discrepancy—none of the animals in the Children’s Zoo were afflicted. “If it had been any of the known poultry diseases, logically I would have expected the chickens to be sick, and they weren’t.” Another, and vastly more troubling, piece of the puzzle, made its appearance shortly before Labor Day. The New York City Health Department announced an unprecedented outbreak of St. Louis encephalitis, and that several patients had already succumbed. Though not unheard of in warmer climates like Florida and Louisiana, this mosquito-borne disease hadn’t been seen in the New York City area since the 1800s. “I was struck with the spatial relationship between the encephalitic birds and the encephalitic people,” McNamara says. “That’s when I made the intuitive leap as a comparative pathologist.” She contacted the New York City public health authorities to suggest that there was a possible link between the two. Her theory met with skepticism from local officials. The hypothesis McNamara offered fit no previously recorded disease pattern, and with increasing concern, the pathologist turned to contacts at the National Veterinary Services Laboratory in Ames, Iowa, and the United States Army Medical Research Institute for Infectious Diseases in Fort Detrick, Md. The results came quickly and bore out McNamara’s hunch—within three days, the Ames facility confirmed that the disease wasn’t any of the known veterinary diseases and categorized the germ as a flavivirus, a class of microbes that includes yellow fever, Hepatitis C, and St. Louis encephalitis. However, the Army’s medical lab ruled out St. Louis encephalitis and instead found that the new samples matched specimens of West Nile virus, first isolated in Uganda in 1937. Prior to this event, it had never been known to cause disease in birds and had never been recorded in the Americas. Portrait of a Microbe McNamara sees little value in wondering how West Nile found its way to the United States. It’s an unavoidable risk that comes as a consequence of global transportation and commerce. Her attitude is matter-of-fact. “The question isn’t how it got here, but how many other things are here that we don’t know about.” West Nile has proven to be a tenacious and disconcerting intruder. As the bug has reemerged every summer since, it has raced across the country with disconcerting speed. McNamara gives a wry laugh when she recalls last year’s efforts to track the disease. “In the past year, the virus swept across the country so fast . . . every day it had moved across another state.” She expects that by the end of this next season, it will be a problem that zoos nationwide will have to face. For conservationists, the spread of West Nile poses troubling scenarios. Bird species that humans have struggled to remove from the brink of extinction could be in jeopardy again in short order. Kelly McGrath, spokesperson for Chicago’s Lincoln Park Zoo, says the danger is very real. “This is a devastating disease for wildlife. There’s a possibility West Nile could knock the American bald eagle back onto the Endangered Species List. We got them off just about five years ago.” The facts are sobering. Mosquitoes transmit West Nile, making it a “warm weather” disease. At present, there is a vaccine available only for horses, zebras, and ponies; attempts to use it more widely in other animal groups have so far not met with much success. There is no treatment for the disease once contracted, and mortality rates vary wildly from species to species—crows suffer mortality rates of nearly 100 percent experimentally, and for other animals, West Nile is a serious, sometimes fatal threat. On the upside, individuals that recover from the disease are conferred with lifelong immunity. Unfortunately, there may also be long-term complications that are not well understood. McNamara has seen troubling long-term consequences for some animals. “Even though we’ve had birds that survived West Nile, they may have had so much damage . . . they may not live as long a life as they would have had they not been infected. Because I’m seeing so much virus in the reproductive tissues of birds,” says the pathologist, “I don’t know what happens to all those chicks that fail to hatch.” At present the Centers for Disease Control (CDC) still advises that West Nile poses a very limited risk to humans. McNamara is not quite as sanguine. “We still don’t have anywhere near the information that we need on this virus.” What’s a Zoo to Do? In spite of the threat West Nile presents to zoos, as institutions they can put in place a wide assortment of procedures to greatly reduce the risk of the virus, educate the public both within and beyond the zoo boundaries, and add to the expanding research effort to understand the disease and find viable vaccines. First and foremost, zoos should initiate aggressive mosquito abatement programs. Many of these techniques are well established but all too often ignored. Standing water in ditches, barrels, tanks, and marshy areas should be drained if possible. For ponds or other permanent bodies of water, there are larvacides available to kill mosquitoes before they hatch. Mosquito traps are useful in reducing populations of adult mosquitoes. There have been some innovations in trap design, including a new model that uses CO2, which the insects find hard to resist. “It almost vacuums mosquitoes from the area,” says McNamara, “It’s like a mosquito magnet.” The Lincoln Park Zoo also stocks mosquito-larvae-eating fish, called golden roaches, in its ponds. Zoos can further reduce the risk of infection by getting the most susceptible animals inside or providing shelter before dusk and keeping them protected until after the sun is up. For equine animals like horses, zebras, and ponies, a vaccine is on the market and strongly recommended—injections should be administered just before the start of the mosquito season. In the event of infection, animals do not have to be destroyed. Two-thirds will recover if given standard supportive treatment for a viral infection. A methodical, coherent surveillance effort among zoos is essential if progress is going to be made against West Nile. Lincoln Park Zoo’s epidemiologist, Dr. Dominic Travis, heads the AZA-sponsored and CDC-funded National West Nile Surveillance Plan, responsible for collating and analyzing all West Nile data. Participating AZA institutions can get free testing of their animals. Zoos are also encouraged to trap and test mosquitoes in an ongoing effort to determine where the disease is present from year to year. That ongoing investigation can succeed only if zoos maintain scrupulous medical records on their animals and follow accepted protocols for handling and analyzing samples. This entails taking necropsies on all dead animals, banking tissue samples in formalyn, and freezing them properly for future study. Unhatched chicks from exposed adults should also be stored and sent to Cornell University’s Veterinary Diagnostic Laboratory. Zoos can report an incidence of West Nile without fear of unwanted publicity. Thanks to guidelines hammered out in meetings involving the CDC, the AZA, and wildlife organizations, stricken animals can be reported with confidentiality, and are reported by local authorities simply as “dead captive birds.” Explains McNamara, “The CDC realized that it really made no sense to say, ‘Death and pestilence at the Bronx Zoo,’ when there were 50 dead crows in the park across the street. It was just sensationalism, and it wasn’t necessary.” McNamara is convinced that if proper regimens and infrastructures are in place, zoos are uniquely equipped to monitor the disease and offer valuable information to local public health authorities and organizations like the CDC. Her take is optimistic. “We have to recognize that we’re a very specialized group, with specialized interests. In situations like this we need funding to do the kinds of research that has to be done to get answers.” However, no function the zoo performs is more critical than disseminating accurate information to the public, and informing them of measures they can take to reduce their risk and help monitor the disease. The prescriptions for diminishing exposure are familiar but often ignored. Applying insect repellent containing DEET when heading outdoors, wearing long-sleeved clothing and pants whenever possible, and staying indoors in the dawn and dusk hours are commonsense precautions that should continually be reinforced. | The Lincoln Park Zoo has led the way in demonstrating how zoos can meet West Nile head on through aggressive public relations efforts. “Our feeling is that the more we educate the public about it, the better they’re going to feel,” says Lincoln Park’s McGrath. “I think it’s a mistake for any zoo, any organization to be afraid of this.” The Chicago institution uses every tool at its disposal to inform visitors about West Nile and the measures in place to control it. Public health brochures are there for the taking, and signs are posted by mosquito traps to explain their function. Perhaps most significant, Lincoln Park Zoo has worked in collaboration with Chicago’s general media to spread accurate information on precautions people can take, enlisting help in monitoring the disease, and giving updates on the current state of scientific research about the virus. Those efforts were borne out of McGrath’s belief that an informed public will respond positively to the small risks posed by West Nile. She offers reassurance to other zoos that may suffer losses to the disease. “Visitorship did not decline at all after we announced that our birds had contracted the disease and three had died. I believe it’s because we spent the past couple of years being very proactive on educating people.” Finally, there’s a very obvious reason why the public should feel at ease in their zoos. Zookeepers’ overwhelming concern for the well-being of their collections compels them to diligently assess the health and safety of the park environment. They put in place aggressive mosquito control programs and scrutinize the physical condition of their captive animals. McNamara believes that “ . . . zoos are probably safer than park visitors’ own backyards.” People head to zoos to marvel at the astonishing variety of this planet’s fauna. The West Nile virus should not deter them from visiting animal parks. On the contrary, the greatest lesson zoos can teach about West Nile should be the interconnection we have to all life on Earth. McNamara recommends taking a philosophical view. “This is not the first, and it won’t be the last disease that infects both animals and humans. . . .We’re all in this together.” Contact Info: Whether or not AZA-affiliated institutions have an incidence of West Nile virus, they are strongly encouraged to contact Dr. Travis and Dr. McNamara to get on their information databases. This will help in the event that zoos nationwide need to be notified regarding the disease. Please send a contact name, fax number, and e-mail to the following addresses: • Dr. Dominic Travis—312/742-7225; e-mail: epi@lpz.org. • Kelly McGrath (Lincoln Park Zoo Media Relations)—312/742-2246. • Dr. Tracy McNamara—718/220-7105; e-mail: tmcnamara@wcs.org or drtmcnamara@aol.com. • Zoos with specimens that need evaluating, including unhatched chicks from exposed birds, should contact Dr. Amy Glaser at Cornell’s Veterinary Diagnostic Laboratory—607/253-3924; e-mail: alg@cornell.edu. • AZA-affiliated institutions will find protocols for handling West Nile on the AZA—web site: www.aza.org. • For those interested in a full account of the arrival of West Nile, Dr. McNamara recommends Secret Agents: The Menace of Emerging Infections, by Madeline Drexler (Joseph Henry Books, ISBN #0-309-07638-2).