The bacterium that causes spotted fever rickettsiosis (RMSF) is more likely to infect a human ______________.
a. If an infected tick feeds for several hours
b. When an infected tick initially penetrates the skin
c. When contaminated tick feces dry and become airborne
d. If the human is exposed to rodent feces containing the bacterium

검증된 단계별 안내

Step 1: Understand the disease transmission mechanism of Rocky Mountain spotted fever (RMSF), which is caused by the bacterium Rickettsia rickettsii.

Step 2: Recognize that RMSF is primarily transmitted through the bite of an infected tick, specifically when the tick remains attached and feeds on the human host.

Step 3: Note that the bacterium is not typically transmitted immediately upon tick attachment; it requires the tick to feed for a certain period to transmit the pathogen effectively.

Step 4: Eliminate options that involve transmission through airborne particles or rodent feces, as these are not common routes for RMSF infection.

Step 5: Conclude that the most likely scenario for infection is when an infected tick feeds for several hours, allowing the bacterium to enter the human bloodstream.

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주요 개념

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Transmission Mechanism of Rickettsia rickettsii

Rickettsia rickettsii, the bacterium causing Rocky Mountain spotted fever (RMSF), is primarily transmitted through the bite of infected ticks. The bacterium enters the human host when an infected tick feeds for several hours, allowing the pathogen to move from the tick’s salivary glands into the bloodstream.

Role of Tick Feeding Duration in Infection

The duration of tick attachment is critical for transmission; Rickettsia rickettsii typically requires several hours of tick feeding to be transmitted effectively. Early removal of ticks reduces the risk of infection because the bacteria need time to migrate from the tick to the host.

Differences Between Transmission Routes of Rickettsial Diseases

Not all rickettsial diseases transmit the same way; for RMSF, airborne transmission or contact with rodent feces is not a common route. Instead, direct tick bite and prolonged feeding are essential, distinguishing RMSF from other diseases like typhus, which may involve contaminated feces.