Serologic diagnosis of epidemic typhus fever

Microagglutination (MA), microcomplement-fixation (CF), indirect microimmunofluorescence (micro-IF) and Weil-Felix (WF) tests were compared for sensitivity and specificity in detection of antibodies against Rickettsia prowazekii and for serologic diagnosis of epidemic typhus fever. Paired sera from hospitalized Ethiopian patients suffering from febrile illness were examined. Purified particulate rickettsial antigens used in MA, CF and micro-IF tests were made from infected yolk sacs by differential centrifugation from molar NaCl and from NaCl-sucrose, D20=1.1491, pH 5.5. In sensitivity the tests ranked micro-IF greater than MA greater than CF greater than WF. Use of specific anti-IgG and anti-IgM sera in parallel micro-IF tests made it possible to differentiate cases of recrudescent epidemic typhus (Brill-Zinsser disease) from primary epidemic typhus cases. Antibodies reacting in high titer with R. canada were produced by 86% of patients with rising antibody titers against R. prowazekii.