LETHBRIDGE, Alta. – A livestock disease almost never seen in Canada continues to restrict the movement of cattle into the country.
Bluetongue is commonly found in warm, dry areas of the southern United States.
Canada remains bluetongue free with the exception of a few cases in specially monitored cattle herds in the Okanagan Valley in 1987, 1988 and 1998.
“We maintain this free status through import regulations,” said Agriculture Canada entomologist Tim Lysyk during a national beef science seminar in Lethbridge.
Canada and the U.S. are jointly trying to find out if bluetongue could enter Canada through insects and if Canada might have an insect species that can support the virus. It is believed the insect that carries the disease cannot survive in colder climates.
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Lysyk said it is unclear whether cattle infected with the virus could spread the disease further among sheep, cattle and wildlife.
Cattle producers on both sides of the border want to trade livestock without costly bluetongue detection tests required for import into Canada during summer months. The restricted feeder program allows feeder steers and heifers from northern states to enter Canada without testing from Oct.1 until March 31.
The disease first appeared in Africa 40 years ago. Insects responsible for spreading bluetongue are small biting midges called “no-see-ums” or sand flies. They are part of an insect family known as culicoides and are difficult to monitor because infectious insects are hard to differentiate from the benign group.
“It’s been really difficult to get a handle on how the vector might affect us,” Lysyk said.
Cullicoides sonoreusis is the main culprit and is hard to detect. There are three subspecies of this tiny insect that are differentiated mainly by the male genitals. In 1988, some of the insects were discovered as far north as Lethbridge.
“We don’t really know the upper limit of its distribution. It probably occurs in a broad area,” Lysyk said.
Bluetongue can kill sheep and cause abortions in cattle. Sheep experience fever, hemorrhaging, lameness, ulceration of the dental pad and inflamed lungs.
