Endemic typhus is caused by which Rickettsia species?

• A. Rickettsia akari
• B. Rickettsia conorii
• C. Rickettsia prowazekii
• D. Rickettsia typhi

Answer: (D)

Endemic typhus is caused by Rickettsia typhi. It is transmitted to humans mainly by fleas that feed on rats, with the rat flea Xenopsylla cheopis serving as a classic vector and rats as the primary reservoir. This flea-driven, rodent-associated cycle distinguishes murine (endemic) typhus from other rickettsial diseases: epidemic typhus is caused by Rickettsia prowazekii and spread by body lice; rickettsialpox is caused by Rickettsia akari and linked to mites; Mediterranean spotted fever is caused by Rickettsia conorii and transmitted by ticks. So the combination of the causative species and its flea-mediated rat reservoir defines endemic typhus. Clinically, it presents with fever, headache, and often a rash, and is treatable with doxycycline.