The Microbial Flora of the Rocky Mountain Wood Tick, Dermacentor andersoni Stiles

Abstract

The internal microbial flora of 2502 specimens of the Rocky Mt. wood tick, D. andersoni, obtained from various sources, included 77 strains of bacteria, 2 strains of yeasts, at least 1 rickettsia (that of Rocky Mt. spotted fever), 1 rickettsia-like organism, and 1 strain of bacteriophage. No acid-fast bacteria, molds, spirochaetes or motile protozoa were observed in any of the ticks examined. Each of the 77 strains of bacteria were studied in detail with respect to their cultural, morphologic, physiologic, and pathogenic characteristics. Of 2016 unfed adult ticks, only 1.6% harbored bacteria, but of 486 recently fed ticks, bacteria were found in a minimum % of 9.1. One possible explanation of the greater number of bacteria in recently fed ticks is the exptl. finding that feeding ticks can ingest bacteria from the surface of skin to which they are attached. The evidence suggests that the bacterial flora of D. andersoni is a fortuitous one consisting chiefly of adventitious organisms apparently acquired from its hosts.