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Author: Hon A/Prof Amanda Oakley, Dermatologist, Hamilton, New Zealand, 2002. Updated, December 2017.
Rickettsial disease encompasses a group of diseases caused by the microorganisms, rickettsiae.
Rickettsiae are bacteria that can only survive inside cells. Rickettsial diseases vary considerably in severity from self-limiting mild illnesses to severe life-threatening infections, particularly if complications arise. The organisms cause disease by damaging blood vessels in various tissues and organs. In severe cases, multiple tissues and organs are affected.
Rickettsial diseases fall into three groups.
Other rickettsial diseases
Rickettsial diseases occur all over the world but some types of rickettsial diseases are more prevalent in certain geographic locations. They are rare in New Zealand.
Most rickettsial diseases are spread to humans by arthropods such as ticks, lice, mites and fleas.
Rocky mountain spotted fever: R rickettsii
Rickettsialpox: R akari
Boutonneuse fever: R conorii
Louse-borne typhus: R prowazekii
Murine typhus: R typhi and R felis
Tsutsugamushi disease: Orientia tsutsugamushi
Signs and symptoms differ slightly depending on the type of rickettsial disease. However, like other viral or bacterial exanthems, most patients present with fever, headache and malaise (feeling generally unwell) and a widespread rash of some description.
Rocky mountain spotted fever
Serology is the mainstay to confirm diagnosis of rickettsial diseases. This is a blood test that detects the presence of antibodies to rickettsial antigens.
All rickettsial diseases should be treated with antibiotic therapy. They should be started early in the first week of illness to be most effective and to produce a good outcome. Doxycycline is the drug of choice. Chloramphenicol may be used as an alternative. Supportive therapy with electrolyte and fluid maintenance are also essential to the management of patients with rickettsial diseases, particularly if there are signs of low blood pressure, electrolyte disturbances, and blood coagulation (clotting) problems (DIC).
Rickettsialpox is a self-limiting disease and occasionally antibiotics may not be necessary, especially if the condition is mild and/or the patient is an infant or young child.
Complications are uncommon for most rickettsial diseases, especially if diagnosed early and appropriate treatment initiated promptly. Rickettsialpox is a self-limiting disease and has no complications. Complications that may occur in some rickettsial diseases include:
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