Ehrlichia canis: Is It a Pathogen for Humans and Other Primates?

Ehrlichioses and anaplasmosis are among the most commonly reported tick-borne diseases in humans and some animal species. Ehrlichia canis is the causative agent of canine monocytic ehrlichiosis; it primarily affects dogs and is usually transmitted by Rhipicephalus sanguineus ticks. Some reports suggest that this bacterium is a zoonotic pathogen capable of causing clinical symptoms consistent with human monocytotropic ehrlichiosis caused by Ehrlichia chaffeensis. Non-human primates seem to be susceptible to E. canis-infection, although it is not clear whether the bacterium can cause disease in these mammals. The number of cases of E. canis infections in human beings and other primates could be underestimated, mainly because inappropriate laboratory diagnoses are often carried out. Serological tests do not distinguish infection by E. canis from those due to other ehrlichial species; therefore, a correct diagnosis is possible only through molecular methods. Furthermore, E. canis is not usually recognized by veterinarians and clinicians as a possible pathogen of primates, and it is not included in the panel of tick-borne pathogens routinely investigated. Further studies are pivotal to verify the pathogenicity of E. canis in primates, and epidemiological investigations are needed to monitor its spread in animal and tick species not usually associated with this agent.