AFRICAN TICK BITE FEVER
By Gary M. White, MD
African tick bite fever (ATBF) is a self-limited disease caused by R. africae, an intracellular bacterium.
- The organism is transmitted by the tick vectors of the amblyomma genus.
- It has been reported in more than 15 African countries and appears to be an emerging cause of influenza-like illness in travelers.
- It is characterized by fever, myalgia, headache, regional lymphadenitis, and one or more inoculation eschars.
After an incubation period of 5 to 10 days, patients have symptoms that include myalgias, arthralgias, fever, and headache: 53% to 100% of patients have at least 1 inoculation eschar (so called tache noir). Patients may develop diffuse macular or vesicular skin eruptions and rarely neuropsychiatric symptoms, myocarditis, and subacute neuropathy.
Rarely, a reactive arthritis may complicate 5% of travel-associated ATBF cases, and some patients may develop subacute cranial or peripheral neuropathy.
The diagnosis may be confirmed in several ways [Infect Ecol Epidemiol. 2017 Aug 2;7(1):1343081]. Seroconversion typical occurs weeks to a month after onset. More immediate results may be obtained using swabs, fluid and skin biopsy.
- Real-time PCR of a skin biopsy (sequencing of the gltA gene for consistency with R. africae) may be used.
- A drop of fluid from the biopsy may contain a sufficient number of bacteria to also allow for isolation of rickettsiae in Vero cell culture.
- Direct molecular detection by PCR from a swab used for bacteria culture from the eschar may also yield a positive result.
A 7-10 day course of doxycycline is the standard treatment.
Fever and a black eschar in a patient who had been hunting in Africa 2 weeks prior. N Engl J Med 2015; 372:e14
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