HUMAN EHRLICHIOSE, AN EMERGING INFECTIOUS -DISEASE

Ehrlichioses are zoonoses caused by a strictly intracellular bacteria that parasites circulating blood cells. A sequence analysis of the gen e encoding the 16s rRNA allowed to classify these bacteria among the a lpha subgroup of proteobacteria, as closely related to Rickettsia. Int racellular surviving of Ehrlichia in the cell phagosome is related to its ability to inhibit the phagolysosome fusion. Three ehrlichia speci es are responsible for human disease. Ehrlichia sennetsu, the agent of Japanese ehrlichiosis described in 1956, which has since curiously di sappeared, Ehrlichia chaffeensis the agent of Human Monocytic Ehrlichi osis (HME), described only in the USA and transmitted by the American tick, Amblyomma americium, and the Human Granulocytic Ehrlichiosis age nt, described in the USA and Europe, transmitted by Ixodes ticks (Ixod es ricinus in Europe). Diagnosis of HME should be suggested in a febri le patient bitten by a tick in Northen America, while HGE should be ke pt in mind as an alternative diagnosis to Lyme disease. Diagnostic may be confirmed by serology, isolation of the agent on tissue culture, o r by gene amplification and sequencing. Tetracycline is the first line antibiotic in the treatment of Ehrlichioses.