Acquired resistance of pigeons to Argas polonicus larvae.
Young (18 to 90 days old) of both feral and domestic pigeons were infested in the laboratory at 14 and 7 day intervals, respectively, with 100-200 larvae or 10 adults of A. polonicus originating from Czechoslovakia and Poland to see if the host acquired resistance to them. After 5 consecutive infestations, the rejection rate of larvae reached 90-95% and the mean weight of successfully engorging larvae fell from 2.18 to 1.72 mg in the Polish population. Although larvae from later infestations appeared to feed more rapidly, the percentage of larvae which succeeded in moulting also fell, probably due to an inability to take in sufficient blood before being rejected. Hosts sensitized by Polish larvae had a higher level of resistance than those fed on by Czech larvae. Anti-tick antibodies were found in pigeons exposed to larvae, but not in those exposed to adult ticks.