Case Presentation: A 63-year-old man presents with a painful, erythematous lesion on his left thigh. He indicates that the lesion first appeared seven days ago and was followed by the onset fevers, chills, headaches, and body aches. The patient’s past medical history is notable for HIV on antiretroviral therapy with a recent CD4 count of 741. The patient recently returned from a trip to South Africa during which he spent most of his time on a safari. He saw his primary care provider who ordered an initial parasite blood smear and rickettsia serologies which were negative.
His exam is notable for a warm, tender, erythematous lesion two centimeters in diameter with a one-centimeter central eschar on the left thigh. There is also a diffuse morbilliform rash across his chest and upper arms. Lab work is notable for leukopenia (3.8 K/uL), an elevated C-Reactive Protein (10.8 mg/L), a normal chemistry panel, and normal liver function tests. Blood cultures, Malaria antigen, Lyme titers, RPR, Anaplasma phagocytophilum IgG/IgM, Rickettsia conorii antibody panel, Rocky Mountain Spotted Fever Ab IgM and IgG, and three parasite smears are all negative. Given the patient’s recent travel to South Africa, symptoms, exam, and lab findings, a presumptive diagnosis of a Rickettsia Africana infection was made. He clinically improved on antibiotics and was discharged with a fourteen-day course of Doxycycline.
Discussion: Fever in the returning traveler is commonly encountered by hospitalists. Infectious etiologies are among the most common cause and the list of potential infectious causes is extensive. One common and often overlooked cause of fever and rash in travelers from Africa is African tick-bite fever, either Rickettsia conorii or Rickettsia africae. Rickettsia africae is carried by the Amblyomma tick and has an incubation period of six to seven days. The classic symptoms of African tick-bite fever include headache, fever, myalgias, multiple eschars associated with regional lymphadenopathy, and a generalized rash that may be vesicular or morbilliform. The diagnosis of African tick-bite fever is most often clinical, based on a patient’s symptoms and exam findings. Non-specific lab findings include leukopenia, thrombocytopenia, and elevated C-reactive protein. Definitive diagnosis can be made by cultures from an eschar biopsy or by laboratory tests using quantitative polymerase chain reactions, however, these are not commonly performed in clinical practice. The standard treatment for African tick-bite fever is doxycycline 100 milligrams twice per day for 7 to 14 days. Although not endemic in the United States, African tick bite fever is a clinically significant illness in the returning traveler which is often-missed but can be diagnosed with lost cost means and is entirely curable.
Conclusions: 1. African tick bite fever is a rickettsial infection that is a common and overlooked cause of fever and rash in travelers returning from Africa.
2. This condition generally presents with headache, fever, myalgias, multiple eschars, lymphadenopathy, and a generalized rash.
3. The diagnosis of African tick bite fever is generally clinical and based on the patient’s symptoms and exam findings.
4. Doxycycline for 7-14 days is the treatment of choice for African tick bite fever.