Rickettsial Diseases

Members of the order Rickettsiales are small, obligately intracellular, Gram-negative bacteria that reside within an arthropod host (tick, flea, louse, or mite) during part of their life cycle. At least 25 bacterial species belonging to six genera (Rickettsia, Orientia, Ehrlichia, Anaplasma, Neorickettsia, and Neoehrlichia) in this order as well as the related Coxiella genus in the order Legionellales are known agents of human diseases. Typical symptoms include fever, headache, and myalgias. The cutaneous manifestations vary from nearly always present rashes and/or eschars in some spotted fevers and typhus to rare skin eruptions in other conditions. Clinical recognition of the characteristic cutaneous findings and early initiation of empiric antimicrobial treatment with doxycycline is paramount, especially for life-threatening Rocky Mountain spotted fever and other severe rickettsioses.