conorii

Rickettsia conorii is a bacterium of the spotted fever group and the etiologic agent of Mediterranean spotted fever, also known as boutonneuse fever in some regions. Infection is transmitted by hard ticks, principally Rhipicephalus sanguineus, the brown dog tick; human infection occurs after a tick bite or exposure to tick-infested habitats. The incubation period is typically 5 to 7 days.

Clinical features include abrupt onset fever, malaise, headache, and myalgia. A maculopapular rash often appears on day 3 to 5 and may become petechial. A characteristic eschar at the inoculation site, known as tache noire, is frequently observed, especially on the trunk or limbs. Lymphadenopathy can occur, and severe disease may involve other organ systems.

Diagnosis relies on serology, particularly indirect immunofluorescence assay (IFA) showing rising antibodies. PCR can detect rickettsial DNA in blood or skin biopsy. The Weil-Felix test is largely obsolete in routine practice. Laboratory findings may include mild leukopenia or normal white blood cell counts and elevated liver enzymes.

Treatment is with doxycycline and is most effective when started early. Alternatives, such as chloramphenicol, may be used in specific situations or for patients in whom doxycycline is contraindicated. The prognosis is generally favorable with timely therapy; delayed treatment can lead to complications such as central nervous system involvement or disseminated disease.

Epidemiology and prevention: the geographic distribution includes the Mediterranean basin, parts of Southern Europe, Africa, and parts of Asia. Risk factors include dog exposure and tick habitats. Prevention focuses on tick avoidance and control, protective clothing, and repellents, with no vaccine currently available.