Murine typhus: a re-emerging rickettsial zoonotic disease

Murine typhus, caused by Rickettsia typhi, is re-emerging in many parts of the world. The disease is also called endemic typhus to differentiate from epidemic typhus (caused by Rickettsia prowazekii), and sometimes also named flea-borne typhus. Occasionally, literature sources will include Rickettsia felis as a causative agent of flea-borne typhus, but illnesses caused by R. felis are actually flea-borne spotted fever. Murine typhus occurs in warm, coastal areas worldwide. In the United States, most cases are reported from California, Texas, and Hawaii. Murine typhus is usually a self-limited febrile illness but about one-quarter of patients suffer organ complications. The disease is only infrequently fatal. Regarding disease ecology, the historical paradigm is that rats (Rattus rattus and R. norvegicus) are reservoirs of R. typhi worldwide, with rat fleas (Xenopsylla cheopis) as primary vectors. More recently, researchers have proposed an alternative suburban murine typhus transmission cycle involving opossums, cat fleas, cats, and dogs in Texas, California, and rural Mexico. Because cat fleas feed on a variety of mammals, there may be other avenues for R. typhi transmission, including stray or feral cats bringing cat fleas and other infected fleas into proximity with humans and possible aerosolization of infected flea feces. Additional fleas, ticks, lice, and mites may play a role in various areas throughout the world, but a striking lack of fundamental research on this topic makes drawing conclusions difficult. This review provides an overview of the history, epidemiology, diagnosis, and treatment of murine typhus, with special emphasis on its disease ecology.