Rickettsial diseases

Author: Hon A/Prof Amanda Oakley, Dermatologist, Hamilton, New Zealand, 2002. Updated, December 2017.

What are rickettsial diseases?

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.

What are the types of rickettsial diseases?

Rickettsial diseases fall into three groups.

Spotted fever group

Typhus group

Other rickettsial diseases

Ehrlichia, Anaplasma and Coxiella (Q fever) are no longer classified as rickettsial infections.

Who gets 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.

How do you get rickettsial diseases?

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

What are the signs and symptoms of rickettsial diseases?

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


Boutonneuse fever

Louse-borne typhus 

Murine typhus

Scrub typhus

Diagnosis of rickettsial diseases

Serology is the mainstay to confirm diagnosis of rickettsial diseases. This is a blood test that detects the presence of antibodies to rickettsial antigens.

What is the treatment for rickettsial diseases?

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.

What are the complications from rickettsial diseases?

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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