Antibody response after treatment in cattle infected with Psoroptes ovis.

The decline of anti-Psoroptes ovis antibody titres after treatment was studied in six groups of naturally infected cattle. In all trials, using a limiting dilution technique, the specific antibody levels were assessed by ELISA on sera collected at regular intervals up to 78 days post treatment. All individual antibody titres started to decline between day 7 and day 14 post treatment. A linear decrease was observed. In a limited trial, five experimentally infected animals were bled monthly after treatment and seronegativity was reached within four months. The results obtained were in agreement with those obtained in the five field trials. Using a linear regression model, it was estimated by interpolation that most of the animals would have been seronegative within seven months post treatment. These results suggest that the exposure to specific P ovis antigen stops with the end of parasite activity and that dead mites are relatively non-immunogenic.