Abstract

Mammals become hypersensitive to ticks that feed upon them. That hypersensitivity was thought responsible for an observation that a large number of Francisella tularensis-infected Dermacentor variabilis failed to infect a rabbit previously exposed to ticks of that species. In a series of tests of that hypothesis, rabbits sensitized to ticks were often significantly more resistant than control animals to tick-borne tularemia. The conditions that determine the klendusity are thought to be variable and complex but the phenomenon must be of importance in the epidemiology of some arthropod-borne agents.