How are epidemic typhus and trench fever transmitted?

• A. Head lice.
• B. Louse bite.
• C. Mechanically from insect hairs.
• D. Infected louse feces or crushed lice.

Answer: (D)

The key idea is that these diseases are spread by the body louse, and the infectious material is transmitted not by the bite itself but by the louse’s feces (or when a crushed louse releases its contents onto the skin). During feeding, the louse defecates near the bite site; scratching can introduce the infected feces into the wound or mucous membranes, enabling the bacteria to enter the body. This is why the correct choice emphasizes infected louse feces or crushed lice. Head lice are not the usual vectors for these illnesses, and transmission isn’t explained by a simple mechanical transfer from hairs or by the bite alone.