Which condition most commonly activates the dormant form of Rickettsia rickettsii in its tick vector?

• A. Exposure to ultraviolet light
• B. A decrease in environmental humidity
• C. An increase in temperature when the tick feeds on a warm-blooded host
• D. Contact with antibiotics

Answer: (C)

Verified step by step guidance

1. Step 1: Understand the biology of Rickettsia rickettsii, which is an obligate intracellular bacterium transmitted by ticks and known to cause Rocky Mountain spotted fever.
2. Step 2: Recognize that Rickettsia rickettsii can exist in a dormant state within its tick vector, allowing it to survive until conditions favor activation and transmission.
3. Step 3: Identify environmental cues that could signal the tick's feeding activity, such as changes in temperature, humidity, or exposure to light, which might trigger activation of the bacterium.
4. Step 4: Consider that when a tick feeds on a warm-blooded host, the temperature around the bacterium increases, providing a biological signal that the bacterium is now in a suitable environment to become active and replicate.
5. Step 5: Conclude that the most common condition activating dormant Rickettsia rickettsii is an increase in temperature associated with the tick feeding on a warm-blooded host, rather than exposure to ultraviolet light, decreased humidity, or contact with antibiotics.