Question

Vectors do NOT transmit infection by which of the following routes?

• A. Ingestion
• B. Regurgitation
• C. Rubbing of infected feces
• D. Contaminated body fluids

Hint:

Three options are vector feeding or contamination mechanisms; one is how the host swallows a pathogen.

Answer 1

The Correct Option is A

Step 1: The question asks for the route by which an arthropod vector does NOT transmit infection to a human host.
Step 2: Vectors transmit pathogens chiefly by mechanisms tied to feeding and contamination. Regurgitation of infected gut contents into the bite wound is a recognised mechanism, for example plague transmission by the rat flea (blocked proventriculus). So regurgitation is a true mode.
Step 3: Rubbing of infected feces into the bite site or broken skin is another classic mechanism, seen in louse-borne typhus and in Chagas disease where triatomine bug feces are scratched into the wound. So this is a true mode.
Step 4: Transmission through contaminated body fluids of the vector, such as crushing an infected louse and inoculating its fluids, is also a recognised route. So this is a true mode.
Step 5: Ingestion is the route by which the HUMAN host acquires infection from food or water, not a mode by which a biting vector delivers infection. Hence ingestion is the route that vectors do NOT use to transmit infection.
Conclusion: The printed key marks option A (Ingestion), which is medically correct.