Fluorometric measurement of IgG antibody responses in cattle vaccinated with Tritrichomonas foetus

A photometrically-measured indirect fluorescent antibody (IFA) test was developed to measure antibody levels in three heifers vaccinated intramuscularly with two injections (two-week interval) of a vaccine containing formalin-killed Tritrichomonas foetus in oil adjuvant; a separate animal served as a nonvaccinated control. Sera were collected weekly and tested for specific IgG against T. foetus. Antibodies were detectable within two weeks of the initial injection and reached reciprocal titers as high as 7700 as estimated from previously tested reference sera. Titers peaked at six to eight weeks and remained at relatively high levels for the eleven-week study period. The fluorometric assay was easily developed and economical to perform; in addition, it more accurately estimated IgG levels than standard slide IFA tests.