Characterization of rickettsial diseases in a hospital-based population in central Tunisia

In Tunisia, 2 rickettsial groups, spotted fever group and typhus group, have been described since the beginning of the 20th century. Mediterranean spotted fever (MSF), also known as Boutonneuse fever, caused by Rickettsia conorii and transmitted by the dog tick Rhipicephalus sanguineus, is the most frequent rickettsial infection observed. Its seroprevalence in our region is 9% among blood donors and 23% in hospitalized febrile patients. Typhus group rickettsioses, caused by R. typhi and R. prowazekii, are less frequently reported than in the 1970s. Only sporadic cases of typhus were reported in the last decade. However, R. typhi antibodies were present in 3.6% among healthy people and 40% in patients with acute fever of undetermined origin. In the unit of Infectious Diseases at Farhat Hached University Hospital in Sousse, during 2007, 5% of hospitalized patients had eruptive fever, and half of the cases met clinical criteria of MSF and/or were confirmed by rickettsial serology. The majority of cases (90%) were noted in hot seasons, and contact with domestic animals was found in 76%. The most common symptoms were fever (present in all cases), skin rash (in 85% to 98% of cases), and headache (in 69.5% of cases). The clinical triad (fever + rash +"tache noire") was noted in 32 to 61%. Normal blood cells or leukopenia, cytolysis, and thrombopenia were the most frequent biological abnormalities. Complications and malignant forms of rickettsial infections were reported in 3.5 to 6% among hospitalized adult patients. When specific serology was performed, MSF was confirmed in 15%, and we noted an emergence of murine typhus (MT) mistaken for R. conorii or viral infection. Rickettsia felis was identified in 1 patient, whereas 17% of cases remained undetermined. Rickettsia conorii Malish was identified by PCR in skin biopsies. Doxycycline was the antibiotic of choice for rickettsial infections; it was prescribed in the majority of patients, associated with fever defervescence, in a mean of 72 hours. The mean length of stay among hospitalized patients with rickettsial infections was 5.9 days. In conclusion, in our region, MSF and murine typhus are endemic. Doxycycline should be prescribed in patients with acute fever and skin rash, especially in hot seasons. These rickettsioses were characterized by benign prognosis. More skin biopsies are needed to identify other SFG rickettsies.