Anaplasmosis is a disease caused by the bacteria Anaplasma
phagocytophilum, transmitted to humans by tick bites.
It is less common than Lyme disease in California but is
transmitted by the same tick, the western black-legged tick
(Ixodes pacificus). On the east coast of the
United States, the tick vector is the deer tick (Ixodes
scapularis). It is treatable with antibiotics and
rarely fatal. A person who has been bitten by a tick
and develops symptoms of Anapslasmosis should see their
How is Anaplasmosis transmitted?
Anaplasmosis is transmitted through the bite of an infected tick.
If I am bitten by a tick, will I get Anaplasmosis?
Anaplasmosis is uncommon in San Mateo County. In 2016, less
than 1% of adult western black-legged ticks tested positive for
bacteria that cause Anaplasmosis. Checking for ticks
after hiking or camping and removing ticks promptly will reduce
the risk of acquiring the disease.
What are the signs and symptoms of Anaplasmosis?
Nausea / Abdominal pain
People will rarely develop all symptoms, and symptoms vary from
person to person. Symptoms usually develop 1-2 weeks
following a tick bite.