Anaplasmosis Outbreak Quiets Down

“We’re not doing active testing right now unless we have a suspicion of the disease.”

– DR. DOROTHY GEALE, CFIA

An anaplasmosis outbreak in southeastern Manitoba livestock herds is starting to tail off with no new cases reported since earlier this spring.

The last confirmed case on April 26 involved a herd of bison in the Rural Municipality of Stuartburn. That farm is under quarantine and the animals will be retested in fall when the insect season is over, according to the Canadian Food Inspection Agency.

Within the southeast region, CFIA has confirmed anaplasmosis on 15 farms, including 14 in the R. M. of Stuartburn and one in the neighbouring municipality of La Broquerie.

CFIA has tested 4,710 animals in the 15 infected herds and removed 245 positive reactors.

All animals were beef cat-t le except for the bison. Quarantines on all but the bison farm have been lifted.

CFIA has stopped on-farm testing for anaplasmosis during the summer when biting ticks, which transmit the blood-borne disease, are active. The agency is asking producers to watch their herds for clinical signs and will test specific herds if notified.

“We’re not doing active testing right now unless we have a suspicion of the disease,” said Dr. Dorothy Geale, a CFIA senior staff veterinarian for foreign animal diseases.

Geale said testing for anaplasmosis during the vector season is difficult because animals must be tested twice to confirm the disease. In winter, a single test is adequate because the ticks are not around then.

The outbreak in the southeast region came to light when a producer noticed clinical symptoms in his animals and reported the matter to a local veterinarian who contacted CFIA.

CFIA has not been able to finger the source of the outbreak. But Geale said it may have originated in northern Minnesota, where anaplasmosis has been identified on farms near the Canada-U. S. border. One of the infected Manitoba farms is also not far from the border.

Geale said it’s possible that ticks from an infected U. S. animal may have come in contact with a Manitoba animal, although that’s not known for certain. Anaplasmosis can be transferred from one animal to another only through blood-to-blood contact.

Some have suggested wildlife as disease carriers, but Geale said that’s not likely. She said research shows whitetail deer are usually poor carriers of anaplasmosis and tests on elk in Minnesota showed no sign of the disease.

The anaplasmosis outbreak in Manitoba is the largest in Canada since 1983 and the first in the province since 1968.

An earlier outbreak occurred in late 2008 in the rural municipalities of Lac du Bonnet and Alexander. Eight positive herds were identified and 1,700 livestock were tested in the infected herds, with 345 positive animals removed. All herds have since been released from quarantine. The cases came to light during routine CFIA serological disease surveillance.

Altogether, since December 2008, over 10,000 cattle have been tested for anaplasmosis in Manitoba, with 589 cattle and one bison testing positive in 23 herds, said Dr. Lynn Bates, a CFIA veterinary disease control specialist in Winnipeg.

CFIA investigates and tests farms in the immediate area of infected farms. It also conducts trace-in and trace-out movements on farms associated through livestock sales, Bates said.

Livestock which test positive for anaplasmosis are destroyed and their owners compensated. [email protected]

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