COXIELLA-BURNETII ANTIBODY PREVALENCES AMONG HUMAN-POPULATIONS IN NORTHEAST AFRICA DETERMINED BY ENZYME-IMMUNOASSAY

Retrospective serosurveys were conducted to determine the prevalence o f antibody to phase-I Coxiella burnetii among humans in various locati ons of north-east Africa. Sera were tested by the enzyme immunoassay ( EIA). Initially the EIA was compared with the standard indirect fluore scent antibody (IFA) method for the detection of antibody to C. burnet ii. Results indicated that the EIA was slightly less sensitive (88%), but highly specific (94%) and less subjective than the IFA technique. EIA was subsequently adopted for estimating prevalences in the studied human populations. Data obtained by ELA indicated that the prevalence of C. burnetii antibody among adult Egyptian blood donors was 20% (n= 358) in the Suez Canal area, 16% (n=501) in the Nile Valley and 10% (n =427) in the Nile Delta. Among adult patients with acute, undifferenti ated fever in Egypt, the prevalence was 28% (n=50) of acute sera, with seroconversion in 12% of convalescent sera. Antibody to C. burnetii w as detected by ELA in the sera of 25% (n=71) of cattle workers in Egyp t, 10% (n=100) of housewives in Sudan, and 37% (n=104) of adults in no rth-west Somalia. Following a fever outbreak affecting all ages in nor thern Sudan, IgG antibody to C. burnetii was present in 54% of the feb rile persons (n=185) and in 53% of afebrile persons (n=186). IgM antib ody to C. burnetii was demonstrated in 29% of the febrile persons and 15% of the afebrile persons. These results implicate C. burnetii as a possibly important and under-reported cause of human disease and undia gnosed fevers in north-east Africa.