Local and systemic reactions in cattle to Hypoderma lineatum larval toxin: protection by phenylbutazone.

Soluble toxin of Hypoderma lineatum injected IV induced a severe cardiorespiratory shock syndrome in calves. Intradermal injection of the toxin caused well-defined, edematous wheals comparable with those produced by histamine. Treatment of calves with famphur (organophosphate insecticide; poured on the skin of the calves 24 hours before injection of toxin) did not increase the severity of the effects of the toxin. Treatment of calves with phenylbutazone (20 mg/kg) 20 minutes before injection of toxin protected the calves against the systemic shock syndrome and the local inflammatory reaction. Apparently, the neurotoxic mechanism of the organophosphate insecticide is independent of the action of the Hypoderma toxin per se. Phenylbutazone can control the effects of the Hypoderma toxin.