Cutaneous responses of cattle to extracts from Rhipicephalus appendiculatus larvae.

A component of an extract from Rhipicephalus appendiculatus larval ticks induced an immediate hypersensitivity reaction in sensitized cattle when intra-dermally inoculated. Generally, the magnitude of the cutaneous reaction depended upon the duration of exposure of the cattle to tick infestation. The skin reaction was absent in steers not previously fed on by ticks. Field trials, using the extract in the Narok District of Kenya (Masailand), showed that the skin swelling thus induced was biggest in adult cattle and those over 9 months, moderate in the 6-month age-group and barely palpable in the less-than-1-month age-group.