Anaplasmosis
Pathogen
Anaplasma phagocytophilum
Carried by
Blacklegged / deer tick (Ixodes scapularis); western blacklegged tick
Anaplasmosis is caused by bacteria that infect white blood cells. It's carried by the same blacklegged ticks that spread Lyme and Babesia, so it frequently shows up as a coinfection. It can come on with flu-like intensity and, unlike Lyme, often produces tell-tale changes in routine blood work.
Symptoms
- Fever, chills, and severe headache
- Muscle aches and malaise
- Low white blood cell and platelet counts
- Elevated liver enzymes
- Rash is uncommon (unlike Lyme)
Testing
PCR during the acute phase is the most reliable test; paired antibody testing (drawn weeks apart) confirms it, and a blood smear can occasionally show the bacteria clustered inside neutrophils.
Labs often used in the Lyme community:
See our Testing Guide to understand your options.
Geography
Concentrated in the same Northeast and Upper Midwest states as Lyme, with West Coast cases via the western blacklegged tick.
Explore the Where Ticks Live map to see what's carried in your region.
Treatment overview
Doxycycline is the first-line treatment for all ages and usually works quickly when started early — one reason prompt recognition matters.
Frequently asked questions
How is Anaplasmosis different from Lyme?
It's a different bacterium carried by the same tick. Anaplasmosis tends to cause higher fevers and visible changes in blood counts, while Lyme is more likely to cause a rash and longer-term migrating symptoms. They're often treated together.