Attempted immunisation of crossbred calves (Bos taurus x Bos indicus) by repeated natural attachment of ticks Hyalomma anatolicum anatolicum Koch (1844).

Crossbred calves (Bos taurus x Bos indicus) were repeatedly infested with the ixodid tick, Hyalomma anatolicum anatolicum. The parameters of engorgement, pre-oviposition period, oviposition period, engorged weight, egg batch weight, and per cent hatch of eggs all showed statistically significant differences between first to tenth infestation. Only the time to engorgement did not change. It is concluded that repeated infestations of this tick stimulate acquired resistance.