A Direct Complement-Fixation Test for Detection of Mycoplasma Antibodies in Chicken Serum

Abstract

SUMMARY A direct complement-fixation (CF) test is described that utilizes Mycoplasma gallisepticum (MG) antigen and chicken antiserum. Fixation of guinea pig complement (C') was achieved by incorporating untreated normal chicken serum (UNCHS) directly into guinea pig C'. The factor(s) in normal chicken serum which is responsible for CF could be titrated to obtain maximal serum titers. This factor(s) appears to be relatively labile to freezing and/or thawing, but stable at refrigerator temperature for at least 6 weeks. The CF test was compared with the MG serum-plate (SP) and hemagglutination-inhibition (HI) tests on sera obtained from chickens infected with MG and Mycoplasma synoviae (MS) isolates as well as sera obtained from field flocks. Correlation was good among the three tests. Little cross-reactivity of MG and MS antibodies by CF was encountered. The sensitivity and specificity of the CF test equalled or surpassed the HI test. Preliminary investigations indicate that the CF test may find application in detecting antibodies in chicken sera to some common avian viral agents.