The decline of anti-trypanosomal antibody levels in cattle after treatment with trypanocidal drugs and in the absence of tsetse challenge.

The decline of anti-trypanosomal antibody levels in cattle after treatment with trypanocidal drugs was investigated using an anti-trypanosomal antibody-detection enzyme-linked immunosorbent assay (ELISA). The decline of antibody levels differed between experimental animals but went through two phases. During the first 5 months after trypanocidal drug treatment, the decline is rapid with a monthly average decline of 10% of the average percentage positivity during the treatment. Between months 6 and 13 after treatment, the monthly average decline was only 3.6% of the average percentage positivity at the moment of treatment. It took a total of 13 months for all the experimental animals to become seronegative. The usefulness of the anti-trypanosomal antibody-detection enzyme-linked immunosorbent assay (ELISA) in the monitoring of tsetse control operations is discussed.