Early intervention in anaplasmosis is associated with good outcomes
As blacklegged ticks extend their reach across Canadian provinces, a lesser-known pathogen they carry — Anaplasma phagocytophilum — is quietly becoming the country's second-most common tick-borne disease. A 79-year-old man from rural Ontario, who developed the rare complication of myocarditis, recovered fully after physicians acted on suspicion alone, beginning treatment before confirmation arrived. His case, published in the Canadian Medical Association Journal, is both a clinical warning and a broader reminder that the landscape of infectious disease shifts with the natural world, and medicine must shift with it.
- Anaplasmosis cases are rising sharply in Ontario, Quebec, and Manitoba as blacklegged ticks colonize new territory, yet most Canadians — and many clinicians — have never heard of the disease.
- Its symptoms are deceptively ordinary: fever, fatigue, chills, and weakness that could belong to dozens of illnesses, making it easy to miss without deliberate questioning about tick exposure.
- A 79-year-old immunocompromised man developed myocarditis — only the second such case ever linked to anaplasmosis in medical literature — raising the stakes for what might otherwise seem a manageable diagnosis.
- His physicians did not wait for certainty; they started doxycycline empirically, a decision the case report frames as the critical turning point in his survival and full recovery.
- Front-line clinicians are now being urged to routinely screen for tick exposure and treat on suspicion, because half to three-quarters of infected patients never recall the bite that changed everything.
A 79-year-old man from rural eastern Ontario came to hospital with fever, chills, profound weakness, and a recent fall. Immunocompromised and accustomed to working in the woods, he could not recall a tick bite. His doctors suspected a tick-borne illness, ordered a PCR panel, and started doxycycline without waiting for results — a decision that would prove decisive.
The test confirmed anaplasmosis, now Canada's second-most common tick-borne disease, though one that remains largely unknown to the public. More striking still, further testing revealed he had developed myocarditis — inflammation of the heart muscle — a complication linked to anaplasmosis only once before in the entire medical literature.
After two weeks of doxycycline, he was discharged. Four months later, his heart function had normalized and he had no lasting symptoms. The case was published in the Canadian Medical Association Journal by Dr. Michael Quon and colleagues at The Ottawa Hospital, not as a curiosity but as a call to action.
Blacklegged ticks — the same species that spreads Lyme disease — have been expanding across Canadian provinces for years, carrying anaplasmosis with them. The disease announces itself with fever, headache, and weakness: symptoms too generic to point anywhere specific unless a clinician thinks to ask about tick exposure, time spent near deer or pets, or travel through endemic regions.
The authors stress that empiric treatment should never wait for confirmed test results when the clinical picture fits. Half to three-quarters of infected patients never remember being bitten. As tick-borne disease becomes an increasingly routine feature of Canadian medicine, the lesson this case offers is simple and urgent: ask the question, and treat before certainty arrives.
A 79-year-old man from rural eastern Ontario arrived at his local hospital with fever, fatigue, chills, and weakness so severe he had fallen. He was immunocompromised, taking medications to suppress his immune system for an underlying autoimmune condition. He worked regularly in the woods but could not remember being bitten by a tick. The doctors suspected infection and ran tests—blood work, a PCR test for tick-borne pathogens—while starting him on doxycycline, a broad-spectrum antibiotic commonly used when anaplasmosis or Lyme disease is suspected.
The PCR came back positive for anaplasmosis, a disease most Canadians have never heard of, even though it is now the country's second-most common tick-borne illness. The diagnosis was confirmed, and the medical team continued the doxycycline for two weeks. What made this case unusual enough to be published in the Canadian Medical Association Journal was what the tests revealed next: the man had developed myocarditis, inflammation of the heart muscle. This complication had been reported in connection with anaplasmosis only once before in the medical literature.
Anaplasmosis is spread by blacklegged ticks, the same insects that carry Lyme disease. As these ticks have expanded their range across Canada over recent years, cases of anaplasmosis have risen sharply. Ontario has the highest burden, but Quebec and Manitoba are seeing increases too. The disease itself announces itself with fever, weakness, headache, and sometimes gastrointestinal symptoms—nothing distinctive enough to point a clinician toward a specific diagnosis without asking the right questions and ordering the right tests.
Dr. Michael Quon, a general internal medicine specialist at The Ottawa Hospital and assistant professor at the University of Ottawa, co-authored the case report with colleagues to alert front-line physicians that anaplasmosis deserves serious consideration in their diagnostic thinking. "As the incidence of tick-borne diseases rises rapidly across Canada," he and his co-authors wrote, "considering anaplasmosis as a possible pathogen is increasingly important for front-line clinicians." The challenge is that many patients with early Lyme disease—and presumably anaplasmosis—do not remember being bitten. Half to three-quarters of people infected never recall the tick itself.
What saved this man's life was that his doctors did not wait for perfect certainty. They saw a clinical picture consistent with tick-borne disease and started doxycycline empirically, without waiting for test results to come back. The authors emphasize this point: "Empiric antimicrobial therapy with doxycycline should not be delayed in a patient with a suggestive clinical presentation." After 14 days of treatment, the man was discharged. Four months later, he had no lingering symptoms and his heart function had returned to normal.
The case serves as a teaching moment for a health system increasingly confronted with tick-borne disease. Clinicians are urged to ask patients about tick exposure, proximity to deer or pets, and whether they use preventive measures like DEET or protective clothing. They should ask about prior Lyme disease. And when the clinical picture fits—fever, weakness, and exposure risk in an endemic region—they should not hesitate to start treatment. Early intervention in anaplasmosis is associated with good outcomes, even when serious complications like myocarditis develop. As blacklegged ticks continue to establish themselves in new Canadian provinces, this knowledge may become as routine as screening for Lyme disease itself.
Notable Quotes
As the incidence of tick-borne diseases rises rapidly across Canada, considering anaplasmosis as a possible pathogen is increasingly important for front-line clinicians— Dr. Michael Quon, general internal medicine specialist at The Ottawa Hospital
Empiric antimicrobial therapy with doxycycline should not be delayed in a patient with a suggestive clinical presentation— Dr. Quon and co-authors in the Canadian Medical Association Journal
The Hearth Conversation Another angle on the story
Why is anaplasmosis suddenly becoming a bigger problem in Canada now?
The blacklegged ticks that carry it have been expanding northward and into new provinces for years. It's partly climate, partly the ticks' own range expansion. Ontario has had cases for a while, but now we're seeing them in Quebec and Manitoba too.
If half of Lyme disease patients don't remember tick bites, how do doctors even know to test for this?
That's the hard part. The symptoms are so generic—fever, weakness, fatigue—that without a high index of suspicion and a good history, it's easy to miss. The case in the journal is a teaching tool partly because the man didn't remember a bite either, but he worked in the woods regularly.
What made this particular case serious enough to publish?
The myocarditis. Heart inflammation from anaplasmosis had only been reported once before. This man was immunocompromised, which may have made him more vulnerable to complications, but it showed that clinicians need to think beyond the typical presentation.
So doxycycline is the answer?
It's the answer if you start it early and empirically—meaning before you have confirmed test results. The man got it right away based on clinical suspicion, and that likely prevented worse outcomes. Waiting for perfect confirmation can cost time you don't have.
What should someone do if they live in an endemic area?
Use DEET, wear protective clothing, check yourself for ticks after being outside, and tell your doctor if you've had tick exposure and develop fever or weakness. And if you're a clinician, don't anchor too hard on whether the patient remembers the bite—ask about the exposure risk instead.