Adult ticks of Rhipicephalus appendiculatus were fed on rabbits immunized with antigen–antibody complexes derived from the immunodiffusion reaction in agarose of tick extracts with antisera from rabbits immunized previously with tick extracts. Ticks feeding on the precipitin complex immunized rabbits displayed delayed attachment, prolonged engorgement and extended periods to drop off the host. While final engorgement weight was not affected, the immunization was observed to produce an adverse effect on egg hatchability. Fewer than 10% eggs from ticks fed on immunized animals hatched live larvae compared to greater than 90% live hatchings from ticks fed on controls. The tick antigens responded to by the immunized rabbits were characterized by crossed immunoelectrophoresis. Antisera from precipitin complex immunized animals precipitated four to five separate antigens from immunizing extracts. One (or more) of these antigens may be the target for the observed deleterious effect on tick reproduction.
