Epidemiology, molecular biology, and pathogenic mechanisms of Ehrlichia infections

Ehrlichia are tick-borne, obligately intracellular Gram negative bacteria and are important veterinary and human pathogens with a worldwide distribution. Ehrlichia can cause prolonged or persistent infection in animal hosts. The pathogenesis of Ehrlichia is mediated principally by the immune response. In order to multiple inside host cell, Ehrlichia passively escape host innate immunity (such as pattern recognition receptors) due to lack of typical Gram negative bacterial cell wall components (such as lipopolysacchride and peptidoglycan) and actively encoded proteins that enter into host cell nucleus to manipulate host cell gene expression.