Ehrlichiosis

Ehrlichiosis is closely related to anaplasmosis — both involve bacteria that infect white blood cells, both cause a similar illness, both treat the same way. The main difference is the vector: ehrlichiosis comes primarily from the lone star tick, which is established in a small part of southwestern Ontario and increasingly turning up further afield on migratory birds.

Transmission typically requires several hours of attachment. Same-day tick checks and prompt removal substantially lower the risk.

One to two weeks after a bite:

• Fever
• Severe headache
• Fatigue
• Muscle aches
• Sometimes nausea or vomiting
• A rash in about a third of cases — small spots, often on the trunk or limbs

Bloodwork shows low platelets and elevated liver enzymes, much like anaplasmosis. Severe untreated cases can progress to organ involvement, especially in older or immunocompromised patients.

This week:a flu-like illness with high fever and severe headache, one to two weeks after a tick bite in southern Ontario. Mention the lone star tick if you saw or saved it — the single bright white dot on an adult female’s back is distinctive.

Emergency room: confusion, severe shortness of breath, signs of shock, or any neurological symptoms.

Ehrlichiosis is treated with doxycycline. Most patients respond within 48 hours of starting antibiotics. As with anaplasmosis, treatment shouldn’t wait for lab confirmation when the clinical picture and exposure history fit.

Established cases are rare and concentrated in the lone star tick’s emerging Canadian range — southwestern Ontario. Sporadic cases follow lone stars that arrive on migratory birds, which is why isolated reports turn up elsewhere. PHAC tracks lone star establishment closely; expect both the tick and this illness to expand over the next decade.

Public Health Agency of Canada; Ontario provincial surveillance reports.