Comparison of effects of low and high tick infestations on acquired cattle tick resistance: Hyalomma marginatum marginatum.

Three Holstein calves were infested with low numbers of ticks, two or three pairs of adults Hyalomma marginatum marginatum in cloth bag daily for 21 days. Infestation was carried out during tick proliferation periods. Two months later, cattle leads were challenged with 100 pairs of ticks. Another group of three Holstein calves were infested five times with 100 pairs of adult ticks of the same species. The five infestations were performed two weeks from the previous infestation. Three tick characteristics were recorded for each experiment: survival to detachment, females weight at detachment and egg mass weight. Light continuous infestations did not cause a significant change in this parameter, but every parameter declined gradually in the heavy infestations. Female and egg mass weight reached a significant difference from the first infestation by the fourth infestation. The circulating antibodies anti-salivary glands of Hyalomma m. marginatum showed that light infestation may induce like immuno-suppression. However, there is an inverse relationship between these antibodies and manifestation of resistance when calves were heavily infested. This is discussed in relation to a fraction of produced antibodies against protective antigens, and participation of another effector mechanism.