Crows and horses will be used as early warning signals in the fight against the west Nile virus that is expected to arrive in Alberta this year with migrating birds, say Alberta government officials.
“With the migratory birds returning to Alberta and undoubtedly, in my opinion, some of them are bringing west Nile into the province,” Margo Pybus of Alberta Sustainable Resource Development said during a joint news conference with other government departments to unveil a new west Nile virus plan.
“We’re making the assumption it will arrive in the province this year.”
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Collecting and testing dead crows will be key to detecting the disease this summer.
“If west Nile is there we will be seeing dead crows in the province,” said Pybus, who is encouraging Albertans to bring dead crows to an Alberta Fish and Wildlife office for testing.
Crows are one of the few species of birds found throughout the province and it’s the only bird for which there is a good diagnostic test for west Nile.
Crows also have a high rate of west Nile mortality, dying within three to seven days of exposure.
Once west Nile has been found in one of Alberta’s six natural regions, collection of crows will be stopped in that region. The regions have similar birds, animals and mosquitoes, and Pybus said if the virus is found in a bird, it will mean the virus is in the region.
The virus was found on Alberta’s doorstep last year, in birds in Saskatchewan, Manitoba and Montana.
West Nile is a mosquito-borne virus that is also spread through birds. While Alberta has 43 species of mosquitoes, the culex mosquito, which seems to be the main carrier of the virus in Eastern Canada, is not one of them.
The virus was first detected in Ontario in 2001, believed to have entered Canada through an infected bird.
In 2002, there were 325 confirmed cases in Canada. Alberta had two of them, but it is believed both were contracted outside the province.
For the first time, Alberta has made west Nile virus in horses a reportable disease. Anyone who suspects or knows a horse is infected must report it to the chief provincial veterinarian’s office.
“We are using horses as a sentinel species,” said Gerald Ollis, the province’s chief veterinarian.
Most horses bitten by a mosquito infected with west Nile virus will not develop clinical signs. Up to 35 to 40 percent of horses showing clinical signs of the disease may die or have to be killed because of complications from the disease.
There is no evidence the virus is transmitted from horses to other species, including humans.
Donkeys and mules are in the same classification as horses.
There is no evidence domestic chickens can be infected with the virus, but it’s believed domestic geese can be infected.
All other farm animals such as cattle, sheep and goats can be infected, but with no ill effects once the infection clears their body.
“Many species can be infected but not show symptoms,” Ollis said.
