Prevalence of antibodies to Coxiella burnetti, Rickettsia conorii, and Rickettsia typhi in seven African countries.

The prevalences of antibodies reactive with Coxiella burnetti, Rickettsia conorii, and Rickettsia typhi were determined by indirect fluorescent antibody testing of sera from seven African countries. The seroprevalences of antibodies reactive with C. burnetti and R. conorii in countries from North Africa were similar to those reported from southern Europe. In countries of sub-Saharan Africa, the seroprevalence of antibodies reactive with C. burnetti varied greatly; the generally higher figures for West Africa, where stock breeding is prominent, suggested that domestic animals might be the main reservoirs of infection. The prevalence of antibodies to the recently described species Rickettsia africae was higher than that reported for spotted fever-group rickettsiae from elsewhere in the world and paralleled the distribution of Amblyomma species. Western blot results suggested that the antibodies detected were more likely to be reactive with R. africae than with R. conorii, the main vector of which (Rhipicephalus species) rarely feeds on humans. The seroprevalences of antibodies reactive with R. typhi were higher in coastal regions, where Rattus norvegicus--the natural host of the vector Xenopsylla--is more prevalent, than in inland areas.