Rabbits infested with Ixodes ricinus L. adults: effects of a treatment with cyclosporin A on the biology of ticks fed on naive and immune hosts.

Rabbits have been infested 3 times with 10 female and 10 male Ixodes ricinus. Immunity which is induced when ticks feed on naive animals (1st infestation) perturbs feeding, oviposition and embryogenesis during reinfestations. Treatment of rabbits during a 3rd infestation (resistant animals) with cyclosporin A (CsA), an immunosuppressive agent which works on the cellular compartment (chiefly T helper cells), partially reversed the negative effects of the immunity on the biology of the ticks. Conversely, CsA may also directly affect the reproductive processes of ticks. Thus, the weight of the eggs laid and the egg conversion factor of ticks fed on naive treated hosts (1st infestation) were diminished. In addition, the preoviposition was prolonged, and finally failure in oviposition and hatching occurred more frequently.