Anaplasmataceae Bacteria

Anaplasmataceae is a family of bacteria of the order Rickettsiales that infect vertebrate red blood cells or plasma and are transmitted by ticks, fleas, and lice. The family includes four genera: Anaplasma, Ehrlichia, Neorickettsia, and Wolbachia. Members of the first three genera are intracellular, obligate, gram-negative parasites that reside in cell vacuoles and form characteristic colonies that resemble mulberries, termed morulae.2 The intracellular location of the organisms protects them from the host's antibody response. Howevere, bacteria stimulation of proinflammatory cytokines production is believed to play an important role in activating macrophages that act either directly on infected cells on bacteria during their extracellular phase.3

Two major bacteria species from the family Anaplasmataceae are Anaplasma phagocytophilum and Ehrlichia chaffeensis. Both of these are known to be tick-borne pathogens. Wild animals such as deer or rodents are reservoirs of tick-borne anaplasmosis and ehrlichiosis. Animals which have recovered from the disease may harbor the pathogens for long periods.

Engorged lone-star tick Amblyomma americanum that transmits Ehrlichia bacteria
Source: CDC/ Dr. Amanda Loftis, Dr. William Nicholson, Dr. Will Reeves, Dr. Chris Paddock

Human Granulocytic Ehrlichiosis

Human granulocytic ehrlichiosis is caused by Anaplasma phagocytophilum. The disease is characterized by fever, headache, muscle pain, and various blood abnormalities. The bacteria also causes granulocytic ehrlichiosis in horses, but the disease is not fatal.1


  1. Rickettsial diseases. Didier Raoult, Philippe Parola
  2. The prokaryotes: a handbook on the biology of bacteria, Volume 5. Martin Dworkin, Stanley Falkow
  3. Medical microbiology. Patrick R. Murray, Ken S. Rosenthal, Michael A. Pfaller



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