Malaria surveillance in elimination setting — DTM&H MCQ
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HardEpidemiology, outbreak investigation and public healthMalaria surveillance in elimination settingDTM&H
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Correct answer: B — Reactive case detection around index households with mapping of exposure sites
The correct answer is B, reactive case detection around index households with mapping of exposure sites. In an elimination setting, every locally acquired case is a sentinel event triggering investigation of the index case, screening of household members and neighbours, and mapping of likely exposure locations to define the transmission focus. Low, clustered case numbers near elimination make passive surveillance alone insufficient, whereas focal reactive investigation finds additional asymptomatic infections and delineates the foci so targeted vector control and treatment can follow. Three linked local cases after a case free interval is the classic trigger for case investigation and reactive detection under WHO malaria elimination surveillance protocols, since surveillance itself becomes the principal intervention as incidence falls. Why the other options are wrong: A. Rely on the next annual prevalence survey: an annual survey is far too infrequent to detect an acute, geographically focal cluster in time to interrupt transmission before it amplifies. D. Use stool surveys to map transmission: stool examination detects helminths and enteric pathogens, not Plasmodium, which requires blood film, RDT or PCR; it is the wrong sample entirely. E. Screen distant urban hospitals without village follow-up: this ignores the actual village focus, local vector exposure and cannot identify the source or extent of the cluster. C. Stop vector control because cases are vivax: P. vivax shares the same anopheline vectors and relapses from hepatic hypnozoites, so vector control must continue, especially with confirmed local transmission. Key point: Locally acquired cases near elimination should trigger reactive case detection and exposure site mapping around index households, not passive surveillance or scheduled surveys.
Reference: WHO, Disease surveillance for malaria elimination: an operational manual (World Health Organization, Global Malaria Programme), section on case and foci investigation and reactive case detection, https://www.who.int/publications/i/item/9789241507028