Vertebrates exhibit an innate grooming response to feeding by hematophagous arthropods. This response is augmented by previous exposure to arthropod feeding, which results in immunological sensitization and allows for the subsequent expression of acquired resistance. The result of such a response is the significant protection of the host to subsequent arthropod attack. In addition, this immunologically based response, induced by and directed against the arthropod, apparently imparts the host with protection from disease by interfering with pathogen transmission. To date, this aspect of the epidemiology of arthropod-borne diseases has received little attention despite the obvious potential importance of such a response to the understanding of disease transmission.