FACING an invasion? Posting a line of guards along your border is a good idea. That's exactly what Canadian health authorities are doing-except their sentries will be chickens, dispatched to the country's southern border to serve as an early warning system in case West Nile virus moves up from the US.
Although West Nile virus mainly infects birds, it can be transmitted to humans by mosquitoes. Infected people-especially the elderly-occasionally develop encephalitis. Last summer, the virus struck New York City, making 46 people ill and eventually killing seven, and as a result, the city spent an estimated $10 million on controlling mosquitoes. No human infections have been reported since last summer, but the US Centers for Disease Control and Prevention announced in March that the virus had been found in mosquitoes overwintering in New York. So a new outbreak may yet occur this year.
The virus probably travelled to New York in an imported exotic bird. Although the virus has yet to move north to Canada, the Canadian health authorities plan to catch it in the act if it does. "We are going to be putting out sentinel chicken coops from Saskatchewan to Atlantic Canada," says Harvey Artsob, chief of zoonotic diseases at Health Canada's Laboratory Centre for Disease Control, Ottawa. There will only be a few chicken coops in each province, so the sentinel chickens will be thinly spread along about 2500 kilometres of border. "It's a big country," Artsob notes.
Because the virus doesn't cause any symptoms in chickens, the sentinels will be tested once a week for a viral antibody. Dead birds found in the wild will also be tested.
Author: Kurt Kleiner, Toronto.
New Scientist issue: 20th May 2000
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