Complement-Fixation in Rickettsial Diseases

Abstract

The complement-fixation test for endemic typhus is of value in the detection of active or past infection. Titers of 1:128 and 1:256 may be reached on the 9th or 10th day of illness and 1:4,096 and 1:8,192 on the 14th or 15th day. The complement-fixation reaction is a better criterion of past infection with endemic typhus than the Weil-Felix test since complement-fixing antibodies may be present in significant dilutions up to 5 or more years after the illness. The complement-fixation test may probably be used to differentiate between endemic typhus and Rocky Mt. spotted fevers. Spotted-fever sera tested against a typhus antigen as a rule give a negative reaction, while at the same time a positive Weil-Felix reaction may be obtained in quite high dilutions of serum. Occasionally there may be some cross-fixation of typhus antigen by spotted-fever sera, but usually in low dilutions. Tests similar to those reported in which a spotted-fever antigen is used may elucidate this phase of the problem.