Experts believe urban zoos could help to track swine flu. Credit: Photodisc / Punchstock

Zoos are being drafted by the US government to track the spread of avian influenza this spring. But there seem to be no plans yet to use the zoo network to track the swine flu virus — even though some experts believe it could easily do the job.

With state-of-the-art veterinary labs and expert staff available to look after all kinds of animal species, zoos are well placed to track diseases that move quickly among animal populations.

Zoos carefully monitor every animal in their collection for disease. Visitors who come to watch the lions and seals may not be aware of it, but many zoos even analyse the lowly squirrels and street pigeons that die on their grounds or are eaten by their residents.

The US government is heavily investing in using zoos as a medical-alert network. But so far there is no programme for zoos to track the spread of swine flu, now officially known as influenza A (H1N1).

The system should be able to identify any circulating influenza virus. Amy Glaser , Cornell University

Active surveillance could identify any influenza virus detected and repeated sampling from the same locations would allow researchers to follow changes in viruses over time, explains Amy Glaser, a virologist at Cornell University, who helped to establish and maintain the laboratory-testing component of an earlier zoo-monitoring programme for the West Nile virus. "The system should be able to identify any circulating influenza virus, including the A/H1N1 'swine' influenza virus," she says.

Little is currently known about the transmission of the swine flu virus between different species or its evolutionary origins and such a system could help detect the virus mutating or hopping between hosts.

Lincoln Park Zoo, a small and historic zoo in Chicago, was at the heart of the first disease-monitoring network. In the 1990s, the zoo started collecting tissue samples from horses and related animals to help the US Department of Agriculture Animal and Plant Health Inspection Service (USDA APHIS) monitor tuberculosis in ungulates — hoofed animals.

Researchers at Lincoln Park contacted a few other zoos and got them to collect samples as well. At the time, the collection of data on tuberculosis in exotic ungulates was managed and funded solely by Lincoln Park Zoo. But that soon changed with the outbreak of West Nile virus.

West Nile warning

At a West Nile virus meeting in 2001, Lincoln Park Zoo researchers showed officials from the US Centers for Disease Control and Prevention (CDC) what had been accomplished with ungulate tuberculosis and convinced them to invest in the development of an extensive disease-monitoring network. The network that Lincoln Park then managed for five years tested more than 16,000 biological samples from more than 13,000 animals, from 39 states, housed in 121 zoos accredited by the Association of Zoos and Aquariums, based in Silver Spring, Maryland.

We are well situated to be the canary in the coal mine. Dominic Travis , Lincoln Park Zoo

More than 600 animals were confirmed positive for West Nile virus. Later, when the maps generated by Lincoln Park were compared with CDC-generated maps, researchers found that the presence of the disease in zoo specimens closely matched the movement of the virus in the human population, proving that zoos could be used to effectively track diseases that move readily between animals and people.

This spring, the same zoo network is to begin testing for the H5N1 virus that causes avian influenza, and will work with the USDA APHIS to track the spread of the disease. "Unlike farms, which are far from populated areas, most zoos are right in the middle of cities. We are well situated to be the canary in the coal mine," says Dominic Travis, veterinary epidemiologist at Lincoln Park Zoo.

And because of the quality of their facilities, most zoos will be able to quickly identify different strains. "There are a series of steps for proper diagnosis of highly pathogenic H5N1, but zoos in the network can get preliminary information in a very short amount of time and in the appropriate circumstances, sound the alarm," adds Julia Chosy, research epidemiologist at Lincoln Park Zoo.

From sparrows to swine

While designed to study avian influenza, the system could monitor the spread of swine influenza too. "We have not yet had a discussion [with the USDA APHIS] about whether the network will start testing for swine flu, but this system should be flexible enough to adapt," says Travis.

Yet when asked what role the zoo animal-health network would play in the tracking and management of the current swine flu outbreak, the USDA would not comment directly on whether the system would be activated to search for it in the near future. "Zoological parks are well positioned to help [the] USDA APHIS in monitoring for emergence of foreign animal diseases" says Angela Harless, a spokeswoman for the USDA in Washington DC. Harless added that the project is still in development and would start with avian influenza analysis as the pilot programme.

Glaser says that a current limitation is the government tendency to fund 'single agent' surveillance programmes. "It is shortsighted to focus on a single virus, like influenza or West Nile virus, when the next respiratory coronavirus, adenovirus, paramyxovirus or somethingovirus may be flashing signals of emergence," she says. "Often this has happened in animal populations before affecting humans. With such an extensive system available to us, it is unwise to monitor only the viral species currently causing problems."