Rocky Mountain spotted fever is transmitted by which ticks?

• A. Lone star ticks
• B. Gulf Coast ticks
• C. Brown dog ticks
• D. American dog ticks

Answer: (D)

Rocky Mountain spotted fever is spread by ticks that carry the bacteria Rickettsia rickettsii and can pass it to a person only after feeding for a certain period. In the United States, the most common and well-established vector is the American dog tick. This tick is widely implicated in RMSF cases and is the classic bite you’d associate with transmission, especially in many regions where RMSF is reported.

The other ticks listed can carry RMSF in some situations or areas, but they are not the primary, most consistently linked vectors in most regions. The Gulf Coast tick, lone star tick, and brown dog tick have roles in RMSF transmission in certain contexts, but they do not define the typical transmission pattern for this disease, which is why the American dog tick is the best answer.