[Serological study of rickettsia infections in Niamey, Niger]

Rickettsioses is a possible alternative to presumptive diagnosis of malaria. A serologic study was carried out in 1994 to determine the prevalence of rickettsioses in children under 5 years of age from three different areas of Niamey, Niger. Indirect immunofluorescent assays using the micromethod were performed with antigens for Rickettsia conori, Rickettsia mooseri, and Coxiella burneti. Results were read from a positive threshold of 1/160 up to 1/640. Out of a randomized population of 177 children 35 were positive for at least one antigen: 17.5% for Rickettsia conori, 15.8% for Rickettsia mooseri, and 9.6% for Coxiella burneti. The incidence of positivity for Rickettsia mooseri and Coxiella burneti. was significantly higher in an area where contact between people and animals was particularly close. This high rate of positivity is in agreement with previous reports in other countries in West Africa and suggests that close contact between man and rickettsiae is common. Although dogs carry ticks in Niger, direct contact with Rickettsia conori is probably the most mode of transmission. Rodents like Cricetomys gambianus and Rattus norvegicus carry Rickettsia mooseri and goats and sheep which are often kept in the courtyards of buildings carry Coxiella burneti. The recently identified species Rickettsia africae could be transmitted by other vectors such as cattle ticks.