In the International Animal Health Issues article in last month’s Tracker it was reported that anaplasmosis had been diagnosed in a bison herd in Saskatchewan. This disease is common in the southern, eastern and western United States but has occurred very rarely in Canada. The last time it was reported in Canada was in cattle in 1983 in southern Saskatchewan. In Canada it is a federally reportable disease and is dealt with by authorities as a serious matter.

Anaplasmosis is an infectious disease of cattle and other ruminants caused by a bacteria-like blood parasite called Anaplasma marginale (member of the Richettsiale order). The organism attacks the red blood cells which are then destroyed by the animal’s own immune system. The symptoms seen in affected cattle vary with the severity of the disease but generally relate to the anemia caused by the reduction in the number of red blood cells. In early stages there is fever, depression and loss of appetite. As the disease progresses the animals becomes weak, pale, and short of breath. Animals under 6 months of age are not usually affected by the disease, 6 month to 3 year old animals may or may not be affected, and animals older than 3 years are quite susceptible. Naturally infected bison have not shown any clinical signs of illness but they can be a source of infection to cattle and other bison. Experimentally infected bison have become ill with the disease.

The anaplasmosis parasite is spread between animals through the transmission of red blood cells from an infected animal to a healthy one. Biting insects such as horseflies, deer flies, and mosquitoes as well as ticks have been implicated in spreading the parasite under natural conditions. Hypodermic needles, dehorning tools, and surgical instruments have also shown to spread the disease within a herd of animals.

In the American states that have a problem with the disease, preventative measures are taken to control the spread of the organism amongst the animals. Reducing the insect and tick populations can be attempted and careful attention to sanitation and good husbandry when vaccinating and dehorning should be employed. Animals that are infected can be treated with antibiotics and blood transfusions if necessary. Treatment is usually successful if the animals are treated before the disease becomes advanced. Animals that recover from the disease often become carriers of the disease and a potential source of infection to new animals. Prevention and treatment is employed only in areas where the disease is established and it would be difficult to eradicate.

In Canada treatment is not an option. Anaplasmosis is a reportable disease under the Health of Animals Regulations and is considered foreign to Canada. Whenever it is detected, the Canadian Food Inspection Agency (CFIA) quarantines the herd, tests all of the animals, and orders the slaughter of all positive cases. Thirty five days after the removal of the positive animals the herd is retested and if they are all negative the quarantine is removed. Compensation is awarded for the animals that are destroyed.

To prevent the disease from entering Canada, a strict testing protocol for imported animals is in place. Animals that are imported from the United States must test negative for anaplasmosis (as well as bluteongue, TB, and brucellosis) before entering Canada. They are quarantined for 60 days and then must test negative again for the same diseases before they are released from quarantine. By using this procedure CFIA aims to keep anaplasmosis out of our Canadian herds.