Anaplasmosis Strikes Cattle In Eastern Manitoba

“It seems to be limited to this one area.”


Manitoba’s first anaplasmosis outbreak in 40 years has produced 305 infected cattle, or reactors, on eight farms in the eastern region of the province.

The herds are all in an area west of the Winnipeg River in the rural municipalities of Lac du Bonnet and Alexander, said Dr. Lynn Bates, a veterinary program officer with the Canadian Food Inspection Agency in Winnipeg.

“It seems to be limited to this one area,” she said.

CFIA detected the disease through a periodically conducted national bovine serological survey, said Bates.

The farms were under quarantine last week. The embargo will be lifted once all the cattle who reacted positively to tests have been removed, she said.

The infected cattle will be sent to slaughter. Animals with anaplasmosis become lifetime carriers of the disease after they recover. They may be slaughtered under CFIA inspection for meat if healthy.

CFIA continues to investigate other farms in the area. The agency is also tracing cattle movements off the affected farms, using eartags which the animals wear under a national cattle identification system.

Anaplasmosis, a reportable livestock disease in Canada, is caused by a micro-organism that is a parasite of red blood cells. It is a blood-borne disease which affects domestic and wild ruminants but only cattle show clinical signs.

The last outbreak of anaplasmosis in Manitoba occurred at Marchand in 1969-70. It was eradicated after 232 reactors out of 1,717 cattle tested were slaughtered.

The disease can be transmitted in infected red blood cells by biting insects and through contaminated instruments such as hypodermic needles and dehorning equipment.

Since anaplasmosis is blood-borne and it’s not possible to avoid insects, changing needles frequently and disinfecting dehorning equipment in between use are the best ways to limit exposure to the disease, said Dr. Wayne Lees, Manitoba’s chief veterinarian.

“If you’re in an endemic area or an area where you think anaplasmosis is an issue, it’s probably a worthwhile expense,” said Lees.

A reactor tests positive to two blood tests: one to detect the presence of antibodies and another to detect the DNA of the organism.

The cause of the outbreak is not certain but the disease was most likely brought into the area by infected livestock imported from the United States, Bates said.

Anaplasmosis is endemic in much of the lower continental U. S. It is not a regulated disease in that country and is estimated to cause a loss of US$300 million to the American cattle industry annually.

Canada is considered anaplasmosis free, although its detection in eastern Manitoba probably changes that status. CFIA was obliged to report the case to the Office International des Epizooties (OIE), Bates said.

Canada used to require anaplasmosis testing of live cattle imported from the U. S. during the biting insect season. However, since 2004, new rules have allowed U. S. feeder cattle from 39 states considered to be at low risk for the disease into Canada without testing at any time of the year.

The move was done to remove an irritant with U. S. cattle producers, who saw Canada’s anaplasmosis testing requirement as a non-tariff trade barrier.

However, some Canadian veterinarians believe the action puts Canada’s cattle herd at risk.

Dr. Terry Whiting, a MAFRI veterinarian, wrote in a 2005 paper that opening the border to untested U. S. cattle inevitably means anaplasmosis will occur occasionally in Canada.

“What is not in dispute is that as a result of this change in government import policy, some Canadian cattle will die from anaplasmosis introduced periodically from the United States,” Whiting wrote in the Canadian Veterinary Journal.

“Many veterinarians would probably hold the opinion that financial profiteering at the expense of animal welfare is not responsible animal use.” [email protected]

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