A medical officer posted to a riverine district in Africa learns that the local blackfly population transmits Onchocerca volvulus. Which breeding habitat of the vector explains why damming rivers can be used as a control measure against this disease?

• A Fast-flowing, well-oxygenated streams and rivers ✓
• B Water storage containers around dwellings
• C Stagnant ponds rich in organic matter
• D Tree holes and leaf axils holding rainwater

Explanation

Simulium (blackfly) larvae and pupae attach to submerged rocks and vegetation in fast-flowing, highly oxygenated water, so the immature stages cannot survive in still water. This bionomics underpins control strategies such as dam construction that alter river flow, alongside larviciding of rivers. Stagnant organic water suits Culex, household containers suit Aedes aegypti, and tree holes suit Aedes species such as Ae. simpsoni. This habitat specificity is the classic examination point for onchocerciasis vector control.

Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.