title: Human ehrlichioses: newly recognized infections transmitted by ticks.
abstract: Human ehrlichioses are tick-borne infections caused by bacteria in the genus Ehrlichia. Human monocytic ehrlichiosis is caused by Ehrlichia chaffeensis and human granulocytic ehrlichiosis is caused by an agent similar to Ehrlichia equi. E. chaffeensis infects mononuclear phagocytes and is transmitted by Lone Star ticks (Amblyomma americanum) found in the south central and eastern United States. The agent of human granulocytic ehrlichiosis infects mostly neutrophils, it transmitted by Ixodes species ticks, and occurs mostly in the upper midwest and northeast United States. Despite the undifferentiated presentation of both ehrlichioses with fever, headache, myalgias, leukopenia, thrombocytopenia, and elevated liver enzyme activities, the diagnostic methods are distinct. Occasional severe complications include meningoencephalitis, adult respiratory distress syndrome, shock, and opportunistic infections. Immunocompromised patients are at high risk for death. An adverse outcome is associated with delayed diagnosis and therapy; thus, empirical treatment is advocated. Treatment with doxycycline usually results in prompt defervescence and cure.
authors.affiliation: Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21287, USA.
authors.forename: J S
authors.initials: JS
authors.lastname: Dumler
authors.forename: J S
authors.initials: JS
authors.lastname: Bakken
mesh_terms: D000328:Adult; D000818:Animals; D000900:Anti-Bacterial Agents / Q000627:therapeutic use; D001096:Arachnid Vectors; D004318:Doxycycline / Q000627:therapeutic use; D004536:Ehrlichia / Q000145:classification; D018469:Ehrlichia chaffeensis / Q000502:physiology; D016873:Ehrlichiosis / Q000503:physiopathology / Q000635:transmission*; D005334:Fever / Q000503:physiopathology; D006098:Granulocytes / Q000382:microbiology; D006261:Headache / Q000503:physiopathology; D006801:Humans; D016867:Immunocompromised Host; D018884:Ixodes / Q000382:microbiology; D007970:Leukopenia / Q000503:physiopathology; D008099:Liver / Q000201:enzymology; D008590:Meningoencephalitis / Q000382:microbiology; D009000:Monocytes / Q000382:microbiology; D018482:Muscle, Skeletal / Q000503:physiopathology; D009504:Neutrophils / Q000382:microbiology; D009894:Opportunistic Infections / Q000382:microbiology; D010146:Pain / Q000503:physiopathology; D010586:Phagocytes / Q000382:microbiology; D011379:Prognosis; D012128:Respiratory Distress Syndrome / Q000382:microbiology; D012307:Risk Factors; D012772:Shock, Septic / Q000382:microbiology; D013921:Thrombocytopenia / Q000503:physiopathology; D013987:Ticks / Q000382:microbiology; D014481:United States; D015047:Zoonoses / Q000635:transmission
chemical_list: D000900:Anti-Bacterial Agents; D004318:Doxycycline