Neglected tropical disease mapping — DTM&H MCQ

Correct answer: D — Map prevalence in school-age children

C, map prevalence in school-age children, is correct because school-age children are the WHO-designated sentinel group for schistosomiasis mapping and preventive chemotherapy decisions. Prevalence surveys in this group (usually by urine filtration or Kato-Katz, or point-of-care CCA testing) are cheap, logistically simple to run through the school system, and correlate closely with community-wide transmission intensity. WHO uses defined prevalence thresholds in this age group to decide whether, and how often, mass praziquantel should be delivered through school-based deworming. In a resource-limited setting planning school-based praziquantel, this is therefore the single most efficient and policy-relevant investigation, directly linking a measurable indicator to an actionable treatment decision. Why the other options are wrong: B. Screen air travellers: air travellers are not a representative or exposed population for locally acquired intestinal schistosomiasis and this would not inform local MDA planning at all. E. Test household pets: schistosomiasis is not a zoonosis transmitted through household pets in this context; dogs and cats are not relevant reservoir hosts for the human-infecting species being targeted. C. Survey hospital staff: hospital staff are a self-selected, non-representative sample with occupational rather than environmental exposure, and they are not the target population for school-based treatment. A. Sample adult blood donors: blood donors are a biased convenience sample (generally healthy adults attending clinics) and adults are not the group whose prevalence determines school-based MDA thresholds; using them would misestimate transmission risk in children. Key point: decisions on school-based praziquantel programmes are driven by parasitological (or CCA) prevalence surveys in school-age children measured against WHO prevalence thresholds, not by convenience sampling of unrelated adult groups.

Reference: WHO. Guideline on control and elimination of human schistosomiasis. Geneva: World Health Organization; 2022 (prevalence thresholds in school-age children used to guide preventive chemotherapy/mass drug administration decisions). https://www.ncbi.nlm.nih.gov/books/NBK578396/