Cutaneous and blood leucocyte response of pigeons to larval Argas polonicus feeding.

Dynamics of granular leucocyte response in peripheral blood of naive and sensitized pigeons infested with Argas polonicus larvae was only slightly dissimilar. In both cases a marked increase of heterophil and eosinophil counts and only a mild increase of basophil count were recorded at 6 hours post-infestation. In naive hosts the basophil count increased again at 96 hours post-infestation, but in sensitized hosts it did so as early as 48 hours post-tick attachment and was also accompanied by an increase of eosinophil levels 72 and 96 hours post-infestation. Cutaneous response of sensitized hosts at the tick feeding site was characterized by a large heterophil accumulation at 24 hours post-infestation, by an increased eosinophil count at 48 hours and basophil counts at 72 and 96 hours post-infestation. In primary hosts lesions were characterized by a mild increase of heterophil count later than 48 hours post-infestation and by slight eosinophil accumulations at 24 and 48 hours post-tick attachment, as well as basophil accumulation as late as 96 hours post-infestation. Cutaneous lesions of sensitized hosts were accompanied by apparent inflammatory changes which were mild and sometimes missing in primary hosts. Cytotoxic and degenerative alterations of basophils and other granulocytes were observed as well as vesiculation of secretory granules of basophils. Cutaneous response of sensitized hosts to larval A. polonicus feeding can be characterized as a cutaneous basophil hypersensitivity.