A tick infected with Borrelia burgdorferi bacteria bites a human and transfers the bacteria to the human. The human soon shows signs of Lyme disease. The wound the tick makes on the human’s skin is the pathogen’s:

• A. Portal of exit.
• B. Reservoir.
• C. Portal of entry.
• D. Chain of infection.

Answer: (C)

Verified step by step guidance

1. Understand the terminology related to the chain of infection, which includes the reservoir, portal of exit, mode of transmission, portal of entry, and susceptible host.
2. Identify the reservoir as the natural habitat where the pathogen normally lives and multiplies; in this case, the tick is the reservoir for Borrelia burgdorferi.
3. Recognize the portal of exit as the path by which the pathogen leaves the reservoir; for the tick, this could be saliva or other secretions during feeding.
4. Define the portal of entry as the site through which the pathogen enters a new host; here, the wound created by the tick bite on the human’s skin serves as the portal of entry for the bacteria.
5. Conclude that since the bacteria enter the human through the tick’s bite wound, the wound is the pathogen’s portal of entry, which is why this is the correct answer.