Effect of some drugs on the skin response of tick-resistant cattle to an allergenic extract of larval Rhipicephalus appendiculatus.

When a larval extract from Rhipicephalus appendiculatus was inoculated intradermally into tick-resistant cattle, a cutaneous swelling or bulla was induced, but this did not occur when tick-naive cattle were similarly inoculated. Certain drugs, infused around the inoculation sites just before administration of the extract, affected the development of the swelling. The size of the bulla was lessened by mepyramine maleate, whereas levamisole enhanced the response to the extract. Acetylsalicylic acid and phenylbutazone had no observable effect on the skin reaction. Intravenously administered cyclophosphamide enhanced the response. It is suggested that histamine plays a major role in inducing the skin swelling.