Skip directly to site content Skip directly to page options Skip directly to A-Z link Skip directly to A-Z link Skip directly to A-Z link
Volume 11, Number 11—November 2005
Letter

African Tick-bite Fever in French Travelers

Cite This Article

To the Editor: African tick-bite fever (ATBF) is caused by Rickettsia africae and remains the most common tickborne rickettsiosis in sub-Saharan Africa (1,2). We describe an outbreak of ATBF in 10 of 34 French tourists on their return from South Africa in March 2005. Fever, skin rash, and multiple eschars on the legs developed in the index case-patient (patient 9, Table). After informed consent was obtained, the tourists completed a questionnaire for epidemiologic and clinical data. Acute- and convalescent-phase serum samples were collected when possible for serologic analysis performed at the Unité des Rickettsies. The samples were tested against a panel of antigens including R. typhi, Francisella tularensis, Coxiella burnetii, Borrelia burgdorferi, Anaplasma phagocytophylum, R. felis, R. helvetica, R. conorii subsp. conorii strain Malish, R. africae, R. sibirica mongolotimonae, R. massiliae, and R. slovaca, as previously described (3). A case of symptomatic confirmed ATBF was defined as clinical illness and positive serologic results against R. africae, whereas a case of probable ATBF was defined as typical clinical symptoms without definite serologic evidence of R. africae infection.

Of the 34 travelers, 30 completed the questionnaire and 20 consented to give at least 1 serum sample. After their return to France, symptoms compatible clinically with ATBF developed in 10 of the travelers (Table) and 9 had positive serologic results and/or a seroconversion for spotted fever group-rickettsia, including R. africae (Table). The median time from illness onset to serum testing was 19 days. Thus, 9 of the travelers had probable and 1 had possible (no serum was available) ATBF. Including both probable and possible cases, the illness rate for the whole group was 33.3% (10/30). None of the travelers reported a history of tick bite. The delay between probable exposure and onset of symptoms was 3-10 days (mean ± standard deviation 6.1 ± 1.9 days). Multiple eschars on the legs or arms were seen in 7 (70%) of 10 patients. Eight patients received doxycycline (200 mg per day) for a mean of 10.8 ± 5.9 days (range 5-20), 1 patient received pristinamycin for 8 days, and 1 patient received no treatment. All patients recovered fully without sequela; however, 6 patients reported convalescent-phase asthenia and 1 reported chronic insomnia, which had not occurred previously, for 2 months after the illness. Among the 10 remaining travelers, for whom a serum sample was available, with no clinical evidence of ATBF, 5 were positive for R. africae with only immunoglobulin M (IgM) at a titer of 1:32 in 4 cases and IgG at 1:128 with IgM at 1:32 in 1 case (an acute-phase serum from this patient showed IgG at 1:32 and IgM at 1:32). The 5 other travelers had negative serologic results. Results of serologic testing for other bacteria were negative for all travelers. Twenty-four travelers (80%), including the 10 symptomatic patients, reported using topical insect repellent daily.

Most cases of ATBF are reported in clusters of travelers exposed to ticks during game hunting or safaris, as described here (1,3-5). The estimated incidence of African tick-bite fever in safari travelers is 4%-5.3% (4) but higher incidence may be reported as emphasized in our study. In our study, epidemiologic and clinical data for the 10 symptomatic patients were obtained in accordance with current knowledge of ATBF (2).

Skin biopsy samples remain the best tool to isolate or detect R. africae (2,6). However, specific serologic tests, especially immunofluorescence assays, remain the most widely used microbiologic test worldwide (7). No commercially available test for ATBF exists but due to extensive cross-reactions between spotted fever group rickettsiosis, commercial kits based on the detection of R. conorii antibodies can be used for the diagnosis of ATBF. Most tourists reported using topical insect repellents without any efficacy. Applying repellents to exposed skin provides little protection against ticks because they can crawl underneath clothing and bite untreated portions of the body (8). Thus, treating clothing with synthetic pyrethroid insecticide is recommended to complement the topical repellant (8).

In conclusion, our study emphasizes the importance of ATBF as a common cause of flulike illness in travelers returning from South Africa, but with a higher rate than malaria, typhoid fever, or other tropical fevers. The most important clinical clues are the presence of clustered cases with multiple inoculation eschars. Healthcare professionals who are providing advice should inform persons traveling to endemic areas of Africa of the risk of contracting ATBF and the importance of protecting themselves against tick bites. Chemoprophylaxis with doxycycline is not recommended, however, this recommendation may be evaluated in future clinical trials.

Top

Acknowledgment

We thank Paul Newton for English corrections.

Top

Paul H. Consigny*, Jean-Marc Rolain†, Daniel Mizzi‡, and Didier Raoult§Comments to Author 
Author affiliations: *Institut Pasteur de Paris, Paris, France; †Université de la Méditerranée, Marseille, France; ‡Médecin de Santé au Travail, Plaisir, France; §Faculté de Médecine, Marseille, France

Top

References

  1. Raoult  D, Fournier  PE, Fenollar  F, Jensenius  M, Prioe  T, de Pina  JJ, Rickettsia africae, a tick-borne pathogen in travelers to sub-Saharan Africa. N Engl J Med. 2001;344:150410. DOIPubMedGoogle Scholar
  2. Jensenius  M, Fournier  PE, Kelly  P, Myrvang  B, Raoult  D. African tick bite fever. Lancet Infect Dis. 2003;3:55764. DOIPubMedGoogle Scholar
  3. Fournier  PE, Roux  V, Caumes  E, Donzel  M, Raoult  D. Outbreak of Rickettsia africae infections in participants of an adventure race from South Africa. Clin Infect Dis. 1998;27:31623. DOIPubMedGoogle Scholar
  4. Jensenius  M, Fournier  PE, Vene  S, Hoel  T, Hasle  G, Henriksen  AZ, African tick bite fever in travelers to rural sub-Equatorial Africa. Clin Infect Dis. 2003;36:14117. DOIPubMedGoogle Scholar
  5. McQuiston  JH, Paddock  CD, Singleton  J Jr, Wheeling  JT, Zaki  SR, Childs  JE. Imported spotted fever rickettsioses in United States travelers returning from Africa: a summary of cases confirmed by laboratory testing at the Centers for Disease Control and Prevention, 1999–2002. Am J Trop Med Hyg. 2004;70:98101.PubMedGoogle Scholar
  6. Pretorius  AM, Birtles  RJ. Rickettsia mongolotimonae infection in South Africa. Emerg Infect Dis. 2004;10:1256.PubMedGoogle Scholar
  7. La Scola  B, Raoult  D. Laboratory diagnosis of rickettsioses: current approaches to the diagnosis of old and new rickettsial diseases. J Clin Microbiol. 1997;35:271527.PubMedGoogle Scholar
  8. Parola  P, Raoult  D. Tick-borne bacterial diseases emerging in Europe. Clin Microbiol Infect. 2001;7:803. DOIPubMedGoogle Scholar

Top

Table

Top

Cite This Article

DOI: 10.3201/eid1111.050852

Related Links

Top

Table of Contents – Volume 11, Number 11—November 2005

EID Search Options
presentation_01 Advanced Article Search – Search articles by author and/or keyword.
presentation_01 Articles by Country Search – Search articles by the topic country.
presentation_01 Article Type Search – Search articles by article type and issue.

Top

Comments

Please use the form below to submit correspondence to the authors or contact them at the following address:

Didier Raoult, Unité des Rickettsies, Faculté de Médecine, 27, Boulevard Jean Moulin, 13385 Marseille Cedex 5, France; fax: 33-04-91-38-77-72

Send To

10000 character(s) remaining.

Top

Page created: February 17, 2012
Page updated: February 17, 2012
Page reviewed: February 17, 2012
The conclusions, findings, and opinions expressed by authors contributing to this journal do not necessarily reflect the official position of the U.S. Department of Health and Human Services, the Public Health Service, the Centers for Disease Control and Prevention, or the authors' affiliated institutions. Use of trade names is for identification only and does not imply endorsement by any of the groups named above.
file_external