Bovine anaplasmosis is a disease caused by a special bacterial species, a rickettsia, called Anaplasma marginale (A. marginale). It affects domestic and wild ruminants, including cattle, small ruminants and deer.
In Canada, it mainly affects cattle and has been reported essentially in the Western provinces. In Quebec, it was reported three times: in 2011, 2018 and fall 2022. The latter case involved a cow born to a mother purchased in Ontario. The 2018 report concerned 2 cows purchased in the United States. In the United States, the disease is endemic in the Midwest and Southeast.
Bovine anaplasmosis poses no danger to human health. It should not be confused with human anaplasmosis, also called human granulocytic ehrlichiosis, which is caused by a different microorganism, Anaplasma phagocytophilum. Human anaplasmosis is present in Quebec, particularly in the Eastern Townships.
A. marginale parasitizes the red blood cells of infected animals. Their immune response ends up destroying red blood cells and leads to anemia of varying severity. This results in clinical signs such as fever, anemia, jaundice, weakness, respiratory distress, drop in milk production, or even mortality.
The severity of the disease essentially depends on the age of the animal. Clinical signs are generally mild in animals less than one year old. In animals aged one to two years, the disease can be severe, but is rarely fatal. In animals older than two years, the mortality rate can reach up to 30-50%.
A. marginale is transmitted through the red blood cells of infected animals. Once an animal is infected, it remains infected for life and is a potential source of infection even if it no longer shows clinical signs.
The infection is spread mainly by ticks. In Canada, these include Ixodes scapularis (blacklegged tick). By parasitizing infected animals, ticks become infected, A. marginale multiplies in their bodies and they in turn transmit it to other vulnerable animals.
The infection can also be transmitted through biting flies or contaminated instruments, such as syringes and dehorning instruments. Finally, transplacental transmission from mother to fetus is also possible.
Suspicion of anaplasmosis is based on clinical signs and a history of exposure to risk factors, such as ticks and infected animals.
The definitive diagnosis is based on the detection of A. marginale by the PCR technique.
SAMPLE TO SUBMIT: 3 mL of whole blood (EDTA).
TRANSMISSION OF RESULTS: Test results will be available within 24 to 48 hours.
These tests are conducted from Monday to Friday.
Please feel free to contact us for further information.
André Broes, D.M.V., Ph. D.
Technical Support Manager, Swine and Ruminants