! Bacterial · Blacklegged tick !
Anaplasmosis
moderateA bacterial infection carried by the same blacklegged tick that transmits Lyme disease. Cases often involve both at once. Looks like a bad flu without respiratory symptoms. Treatable with doxycycline; can be severe in older or immunocompromised patients.
- Pathogen
- Anaplasma phagocytophilum (bacterium)
- Vector
- Blacklegged tick (Ixodes scapularis)
- Onset
- 1–2 weeks after the bite.
What it is
Anaplasmosis is caused by a bacterium that infects a specific kind of white blood cell. The blacklegged tick carries it, the same species that carries Lyme, so the risk map is nearly identical. One tick can carry both, which is why co-infections are common.
How long the tick has to be attached
Like Lyme, anaplasmosis generally needs about 24 hours of attachment to transmit. Quick removal cuts the risk sharply.
The first signs to watch for
1–2 weeks after a bite, anaplasmosis comes on like a bad flu:
- High fever
- Severe headache
- Muscle aches
- Chills and shaking
- Fatigue
- Sometimes nausea or vomiting
What’s missing: cough, sore throat, runny nose. A summer flu with none of those, especially after time outdoors, should put anaplasmosis on your doctor’s list. Blood work typically shows low platelets, a low white-cell count, and elevated liver enzymes.
When to see a doctor
This week:a flu-like illness with high fever and severe headache, 1–2 weeks after time outdoors in a Lyme area, with no respiratory symptoms. Tell your doctor about the tick or the time outdoors, since anaplasmosis isn’t always front of mind.
Emergency room: confusion, severe shortness of breath, or signs of shock. Severe anaplasmosis can damage organs, especially in older or immunocompromised patients.
What your doctor will do
Anaplasmosis is treated with doxycycline. Most people respond within 24–48 hours of starting antibiotics. Diagnosis is usually clinical (symptoms plus exposure history) with confirmation from blood work, but treatment shouldn’t wait for the lab result.
Where it shows up in Canada
Anaplasmosis follows the blacklegged tick: southern Ontario, southern Quebec, Nova Scotia, and New Brunswick, with emerging activity in southeastern Manitoba and the BC south coast. Quebec’s Estrie region in particular has seen cases rise over the past several years.
Public Health Agency of Canada (anaplasmosis health-professional guidance); Canada Communicable Disease Report (Estrie regional case series).
Related
Last reviewed
General information only, not medical advice. In an emergency, call 911. Read the full disclaimer.