How is endemic typhus (murine typhus) transmitted?

• A. Bite of a flea.
• B. Flea eggs laid in an open wound.
• C. Feces of a flea rubbed into a wound.
• D. Flea vomitus rubbed into an open wound.

Answer: (C)

Endemic typhus is transmitted by flea feces, not by the bite itself. Infected fleas (often the rat flea) carry the bacteria in their gut. When the flea feeds, it defecates, leaving feces that contain the organism. If those flea feces are scratched or rubbed into a skin wound or mucous membrane, the bacteria can enter the body and cause infection. So the key idea is that infection occurs from contaminated flea feces entering through a break in the skin, rather than from the bite alone. Flea eggs or flea vomitus aren’t the transmission route for this disease, and while a bite might occur, it is the fecal contamination that matters for establishing infection.