Human Granulocytic Anaplasmosis

What is Anaplasmosis?

Anaplasmosis is a tick-borne infection caused by the bacteria, Anaplasma phagocytophilum. Human granulocytic anaplasmosis (HGA), or anaplasmosis, was previously known as human granulocytic ehrlichiosis (HGE).

Anaplasmosis in New York City

A person can develop anaplasmosis if they are bitten by a tick that is infected with A. phagocytophilum. It is transmitted by the blacklegged tick, Ixodes scapularis, the same tick that transmits Lyme disease and babesiosis. Blacklegged ticks may become infected with A. phagocytophilum when feeding on mice, deer, or elk. The tick must be attached at least 12-24 hours to transmit the bacteria that cause anaplasmosis. Not all ticks carry these bacteria. Most patients become infected during the spring and summer in endemic areas, when smaller nymphal ticks are in greatest abundance. Anaplasmosis cannot be spread from person-to-person. Most NYC patients with anaplasmosis become infected after traveling to areas near NYC that are endemic for Lyme disease, including Long Island, Westchester County, and the lower Hudson Valley region of upstate New York. For more information about the blacklegged tick, visit the tick page. The number of cases reported in NYC has ranged from 9 to 27 per year. For more information on the number of NYC residents reported to have anaplasmosis, please visit Epi Query.

How can anaplasmosis be prevented?

For more information on ticks and preventing tick bites, including the use of repellents go to ticks and tick prevention.

How should a tick be removed?

For guidance on the approrpiate way to remove a tick, please go to ticks and tick prevention.

For more information

For the most up to date information visit the CDC anaplasmosis website.

View our brochure on How to Prevent Tick Bites
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Information for Professionals

For more clinical, diagnostic and treatment information please visit Compendiums and Diagnostic and Treatment Guidelines.

Last updated March 2011