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Human Granulocytic Anaplasmosis
Johan S. Bakken, MD, PhDa and J. Stephen Dumler, MD
Infect Dis Clin North Am. 2015 Jun; 29(2): 341–355.
Human granulocytic anaplasmosis (HGA), a deer tick transmitted rickettsial infection caused by Anaplasma phagocytophilum, is a common cause of undifferentiated fever in the Northeast and Upper Midwest U.S. Patients are often initially diagnosed with a mild viral infection, and illness readily resolves in most cases. However, as many as 3% may develop life threatening complications and nearly 1% die from the infection. A history of tick bite and a high degree of clinical suspicion thus warrant consideration for doxycycline treatment in both adults and children, even in the absence of known tick bite, a negative blood film examination, or pending results of specific A. phagocytophilum diagnostic tests such as paired serology or PCR on acute phase blood. Antibody tests and titers should not be used to monitor active infection as detectable antibodies can remain present for years. Moreover, persistent infection has never been reported. While co-infections with Borrelia burgdorferi and Babesia microti occur, there is little evidence to suggest synergism of disease or a role for A. phagocytophilum in chronic illness. Preventive measures include avoiding tick-infested areas, use of tick repellents, and careful searches of skin to remove attached ticks; no vaccine is available.