Infection of colonized cat fleas, Ctenocephalides felis (Bouché), with a rickettsia-like microorganism.

We report the ultrastructure of a rickettsia-like microorganism in a colonized population of the cat flea Ctenocephalides felis (Bouché). The microorganism occurs principally in the cytoplasm of midgut cells, but similar microorganisms were detected in the tracheal matrix, muscle, hypodermis, ovaries, and the epithelial sheath of the testes. The microorganism has a well-defined cell membrane consistent with rickettsia and measures 0.25-0.45 microns in diameter with lengths up to 1.5 microns. It was observed repeatedly in fleas of 1 laboratory colony, including newly emerged non-bloodfed specimens, but not in specimens from several other sources.