Acquisition of immunity in cattle against the blue tick, Boophilus decoloratus.

It is well known that ixodid ticks have the ability to induce immunity in their host. We demonstrate, for the first time, that the tick Boophilus decoloratus induced immunity in its bovine host, since the mean weight of engorged females fed on naive animals dropped from 201.5 mg, to 173.7 mg and 155.3 mg, for females fed on calves previously exposed once and twice; respectively, to B. decoloratus infestations. Ticks which had been transferred from one individual host to another one were able to complete their feeding period on a sensitive host. Such ticks were significantly heavier (mean 245.2 mg) than those fed on a naive (mean 201.5 mg) host for the entire normal feeding period. A negative correlation between the mean weight of the engorged female ticks and the level of serum gamma globulins in the host was also demonstrated.