Case of bovine anaplasmosis confirmed in Ont.

Case of bovine anaplasmosis confirmed in Ont.
Sep 11, 2019

The disease is usually found in cattle from warmer locations

By Diego Flammini
Staff Writer

A cattle disease rarely found in Ontario has popped up on an Elgin County farm.

OMAFRA received confirmation of a positive case of bovine anaplasmosis in a cow-calf herd, the ag ministry announced on Aug. 23.

The disease is classified as “immediately notifiable” under the Health of Animals Act and Animal Health Act, meaning labs must report confirmed or suspected cases of the disease to government officials.

A bacterium called Anaplasma marginale (A. marginale) causes the disease, which attacks red blood cells.

Cows can contract bovine anaplasmosis in multiple ways, said Dr. Jessica Retterath, a veterinarian with Metzger Veterinary Services in Linwood, Ont.

“The disease is spread through the transfer of blood between animals,” she told “In the U.S. it is spread mostly by ticks, but it can be spread through horseflies, needles, processing equipment, and it can be transferred from a cow to an unborn calf.”

The younger the cow is, the better chances it has at recovering from an infection, Retterath said.

“This disease is usually seen in adults and may result in sudden death. It can kill nearly half the cows that get infected with it,” she said. “If you do see one alive, the cow will look pale and out of breath. At the end stage she might start to go jaundice because she’s in liver failure. A juvenile cow between six months and two-years-old might get a little bit sick but they’ll recover.”

A calf under six-months-old may not show any symptoms, she added.

Producers can treat the disease using antibiotics because there’s no licensed vaccine in Canada for it.

Two or three treatments of tetracycline could prevent the sickness but it won’t prevent the infection, Dr. Retterath said.

This most recent confirmation is Ontario’s fourth case of bovine anaplasmosis. The others came in 1996, 2013 and 2016.

The disease is more prevalent in places like California where it’s warm all the time. Ontario doesn’t have that issue, Retterath said.

“We need a nice cold winter to kill ticks,” she said. “Ticks carry it around from animal to animal, and if a farmer brings up one of those animals, they can spread the disease through needles. If you inject (the infected cow) with a vaccine and use the same needle to vaccinate other cows, you’ve just spread the disease.

“The reason we don’t have it in Ontario as much is because it gets so cold in the winter that the ticks can’t survive.”

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