Anaplasmosis, tick-borne disease beyond Lyme, spreading rapidly in Canada

Jul 13, 2026

Anaplasmosis, a tick-borne bacterial infection spread by blacklegged ticks, is rising rapidly in Canada, where it is now the second most common tick-borne disease. A case study in the Canadian Medical Association Journal co-authored by Dr. Michael Quon highlights a 79-year-old Ontario patient who developed myocarditis, a rare cardiac complication. Epidemiologist Jules Koffi reports that six percent of examined ticks carried the bacteria in 2024, up from three percent in 2022. Experts urge immediate treatment with doxycycline upon clinical suspicion, as early symptoms mimic other viruses and patients rarely recall tick bites.

Anaplasmosis emergence in Canada

▪Anaplasmosis is the second most common tick-borne disease in Canada and is spreading rapidly into new parts of North America.
▪A case study in the Canadian Medical Association Journal documented a 79-year-old eastern Ontario man who developed myocarditis, a rare heart muscle inflammation, from anaplasmosis.
▪Untreated anaplasmosis can cause severe complications, including myocarditis, brain inflammation, acute respiratory distress, and kidney failure.

Blacklegged tick range expansion

▪Blacklegged ticks, also known as deer ticks, transmit both Lyme disease and anaplasmosis.
▪Six percent of ticks collected for examination in Canada in 2024 tested positive for the bacteria that causes anaplasmosis, up from three percent in 2022.
▪The prevalence of blacklegged ticks has been rising in Canada from Manitoba eastward, particularly in Ontario, Quebec, and Nova Scotia.

Doxycycline treatment protocol

▪Doxycycline is the first-line antibiotic treatment for both Lyme disease and anaplasmosis.
▪The recommended treatment for anaplasmosis is 100 mg of oral doxycycline twice daily for 10 to 14 days.

Clinical diagnosis considerations

▪Medical experts advise physicians to initiate doxycycline treatment immediately if anaplasmosis is clinically suspected rather than waiting for laboratory confirmation.
▪Anaplasmosis typically presents as a flu-like illness with fever, weakness, headache, and gastrointestinal distress, but usually without the expanding rash characteristic of Lyme disease.
▪Between 50 percent and 75 percent of patients with early Lyme disease do not recall being bitten by a tick, presenting a similar diagnostic challenge for anaplasmosis.

Tick-borne disease prevention measures

▪Preventive measures against tick bites include using EPA-registered insect repellents containing DEET, picaridin, or Icaridin, and wearing protective clothing.
▪Performing daily body checks and removing attached ticks promptly with fine-point tweezers significantly reduces the probability of contracting tick-borne infections.