Am. J. Trop. Med. Hyg., 81(5), 2009, pp. 733-734
doi:10.4269/ajtmh.2009.09-0385;
Copyright © 2009 by The American Society of Tropical Medicine and Hygiene
Tache Noire in African Tick Bite Fever
Dennis Tappe*,
Gerhard Dobler, AND
August Stich
Department of Tropical Medicine, Medical Mission Hospital, Würzburg, Germany; Bundeswehr Institute of Microbiology, Munich, Germany
A fever of 39°C, headache, and malaise developed in a traveler from Germany who had returned from a four-week vacation to the east coast of South Africa. She had visited friends in a rural area and had been on a safari. During the tour, she had discovered a painless lesion on her abdomen. A similar, but smaller lesion had developed on her arm. On examination, two typical eschars were found (Figure 1
). There was no rash or regional lymphadenopathy. The patient did not recall a tick bite and no other travelers in her group were affected.
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FIGURE 1. Initial presentation of eschars on the abdomen (A) and the right upper arm (B) of the patient. A pronounced but diffuse zone of inflammation surrounds a black necrotic center (tache noire). The skin is slightly swollen and shows epidermiolysis. This figure appears in color at www.ajtmh.org.
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C-reactive protein and lactate dehydrogenase levels were increased (5.82 mg/dL and 348 U/L, respectively). A leukocyte count and results of liver function tests were normal. Treatment with doxycycline, 100 mg twice a day, was initiated for suspected African tick bite fever (ATBF) and the patient was seen again four days later (Figure 2). The result of a rickettsial immunofluorescence assay1 using cross-reactive Rickettsia conorii antigen was positive for an acute-phase serum sample and a reconvalescent-phase sample eight weeks later (1:40 and 1:160, respectively). A pan-Rickettsia real-time polymerase chain reaction (PCR)2 of the necrotic center of the lesion (Figure 3) yielded a positive result, confirming the rickettsial etiology of the infection. Fragments of the bacterial citrate synthase gene were amplified by PCR.3 (Figure 4). Amplicons were subsequently sequenced and identified R. africae as causative agent.
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FIGURE 2. Aspect of an abdominal lesion of the patient 4 days after the start of doxycycline treatment. The inflammatory zone is less marked. Epidermis shows shedding in concentric rings. This figure appears in color at www.ajtmh.org.
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FIGURE 3. Aspect of abdominal lesion of the patient 16 days after initial presentation and 9 days after discontinuation of a 7 day course of doxycycline (A). The necrotic center of the lesion has fallen off (B) and left a fibrin-covered ulcer. The necrotic tissue was subjected to a rickettsial-specific polymerase chain reaction. This figure appears in color at www.ajtmh.org.
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FIGURE 4. Polymerase chain reaction (PCR) of the rickettsial citrate synthase gene from a sample of the eschar of the patient. Primers and PCR were used as described by Roux and others.3 An amplicon of the expected size of 381 basepairs was sequenced and showed Rickettsia africae as causative agent of the patient’s infection. Lane 1, patient sample; lane 2, negative control; lane 3, positive control. Lane M, molecular size marker.
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African tick bite fever is endemic in large parts of sub-Saharan Africa and is the most common rickettsiosis in travelers. Aggressive cattle ticks (Amblyomma sp.) act as vectors and reservoirs.1 Unlike Rocky Mountain spotted fever, ATBF is not a life-threatening disease. However, travelers should receive pre-travel advice on how to avoid the infection, i.e., by taking measures to minimize the risk of arthropod bites in bush vegetation likely to be infested with ticks,1 such as wearing protective clothing and inspection of the skin,4 which was not performed in the case presented. The clinical diagnosis is supported by serologic analysis and PCR or culture from skin or blood samples. 1,4,5
Received July 8, 2009.
Accepted for publication August 8, 2009.
* Address correspondence to Dennis Tappe, Department of Tropical Medicine, Medical Mission Hospital, Salvatorstrasse 7, 97067 Würzburg, Germany. E-mail: dtappe{at}hygiene.uni-wuerzburg.de 
Authors’ addresses: Dennis Tappe and August Stich, Department of Tropical Medicine, Medical Mission Hospital, Salvatorstrasse 7, 97067 Würzburg, Germany, E-mails: dtappe{at}hygiene.uni-wuerzburg.de and stich{at}missioklinik.de. Gerhard Dobler, Division of Viral and Rickettsial Diseases, Bundeswehr Institute of Microbiology, Neuherbergstrasse 11, 80937 Munich, Germany, E-mail: gerharddobler{at}bundeswehr.org.
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