Rickettsial diseases are important to consider in acutely unwell patients who recall having been "bitten by something" and/or have travelled to an endemic area.
Patients usually present with a fever and may have a rash (usually maculopapular) or an eschar (the bite site of the ectoparasite).
Epidemic typhus (Rickettsia prowazekii) is now rare but may occur in situations of mass crowding, poverty, famine, and war where there is an increased risk of human body louse infestation.
Doxycycline is the drug of choice for treatment in all patients.
Rickettsial infections (rickettsioses) occur worldwide and are associated with the patient having been bitten by an ectoparasite such as a louse, mite, flea, or tick. Rickettsioses of humans are caused by several related genera of bacteria including Rickettsia species, Orientia tsutsugamushi and O chuto, Anaplasma species, Ehrlichia species, and Neoehrlichia species.
The genus Rickettsia is usually divided into the spotted fever group (SFG), where patients present with fever and spots, and the typhus group (TG). Some scholars also include an ancestral group but this is not yet widely accepted.
The SFG consists of many species, about 20 of which can cause human infection. Different species occur in geographically different parts of the world: for example, Mediterranean spotted fever caused by Rickettsia conorii and Queensland tick typhus caused by R australis. The SFG are mainly tick transmitted. See our separate Rocky Mountain spotted fever topic for detailed information on this condition.
The TG consists of two species: Rickettsia prowazekii (epidemic louse-borne typhus) which is human body louse transmitted, and R typhi (murine typhus) which is rodent flea transmitted. The genus Orientia is mite transmitted.
History and exam
Key diagnostic factors
- fever >38°C
- lymphadenopathy associated with eschar
- exposure to human body lice
- exposure to rodents (rats and mice) and their fleas
- tick bites
- mite bites (Southeast Asia, Oceania, northern Australia)
- travel to the tropics
- exposure to natural vegetation, forests, scrub, bush
- exposure to cat or dog fleas
1st investigations to order
- serum electrolyte levels
- polymerase chain reaction (PCR)
Investigations to consider
- chest x-ray
- trial of doxycycline therapy
- cell cultures
suspected or confirmed rickettsial infection: non-allergic to doxycycline: not pregnant or breastfeeding
suspected or confirmed rickettsial infection: doxycycline allergy: not pregnant or breastfeeding
suspected or confirmed rickettsial infection: pregnant or breastfeeding
- Malaria infection
- Dengue fever
- Chikungunya virus infection
- CDC health information for international travel (the Yellow Book): rickettsial diseases (including spotted fever & typhus fever rickettsioses, scrub typhus, anaplasmosis, and ehrlichioses)
- Communicable disease control manual: rickettsial diseases and Q fever
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