Triatoma (reduviid bug), the vector of Trypanosoma cruzi, is an unusually efficient transmitter of infection compared with most blood-sucking arthropods. What behaviour accounts for this efficiency?
- A It regurgitates infective metacyclic forms into the wound while feeding
- B It passes infective forms in its faeces during or shortly after the blood meal, near the bite site ✓
- C Its mouthparts lacerate tissue deeply, seeding parasites into subcutaneous blood pools
- D It remains attached to the host for days, allowing prolonged transmission
Correct answer: B. It passes infective forms in its faeces during or shortly after the blood meal, near the bite site
Explanation
Triatomine bugs transmit T. cruzi through posterior station infection: infective metacyclic trypomastigotes are passed in the faeces during or soon after feeding, and the parasite enters the body when the host scratches contaminated faeces into the bite wound or mucous membranes. It does not inject parasites with saliva, making option D style direct inoculation incorrect. Regurgitation while feeding is the mechanism in tsetse-transmitted African trypanosomiasis (anterior station transmission), which is the strongest distractor here.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
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