Acquired resistance of pigeons to Argas polonicus larvae.

The acquired resistance of pigeons to Argas polonicus manifests itself in an adverse effect on the feeding and further development of larvae. After five subsequent infestations, the rejection of larvae reached 90-95% and the mean weight of fed larvae dropped down from 2.18 mg to 1.72 mg in the Polish tick population. There appeared also a tendency to more rapid feeding in larvae from later infestations. Also the percentage of moulted larvae decreased, probably as a result of insufficient blood meal taken by larvae on repeatedly challenged hosts. The hosts sensitized by larvae of Polish tick population manifested a higher tick resistance than those sensitized by larvae of Czechoslovak population. No adverse effect has been observed in males and females after repeated infestation of sensitized pigeons. Anti-tick antibodies were detected in the serum of pigeons sensitized by larvae with the aid of counter current immunoelectrophoresis using extracts from whole larvae and from salivary glands of adults as antigen. No antibodies were detected in the serum of pigeons sensitized by adult ticks.