CM3.6-8 | CM3.6-8 | Vector Biology and Control Measures — Summary & Reflection

KEY TAKEAWAYS

Vector-borne diseases remain a major public health priority in India. Key points:

• Vector types: Anopheles (malaria, Brugia malayi filariasis); Aedes aegypti (dengue, chikungunya, Zika); Culex quinquefasciatus (Wuchereria filariasis, Japanese encephalitis); Phlebotomus sandfly (kala-azar); Xenopsylla flea (plague); Pediculus louse (epidemic typhus).
• Mosquito identification: Anopheles rests at 45° angle, larva parallel to surface; Culex/Aedes rest parallel, larvae hang head-down via siphon. Aedes breeds in clean domestic containers; Culex in polluted water; Anopheles in clean slow-moving/stagnant water. Aedes is a day-biter; Anopheles and Culex are night-biters.
• Non-chemical control: Bti (biological larvicide), Gambusia (predatory fish), environmental source reduction, ITN/LLIN (pyrethroids), DEET repellent.
• Insecticide classes: Organochlorines (DDT — Na⁺ channel); Organophosphates (malathion/temephos — irreversible AChE inhibition → antidote: atropine + pralidoxime); Pyrethroids (permethrin/deltamethrin — Na⁺ channel; preferred for ITNs); Carbamates (bendiocarb — reversible AChE inhibition).
• Application methods: IRS (indoor residual spraying — for resting endophilic vectors); larval control (temephos, Bti, oil); space spraying (fogging — rapid response).
• NVBDCP/NCVBDC: Covers malaria, dengue, chikungunya, filariasis, kala-azar, JE. Malaria elimination target: 2027 (India). Kala-azar target: <1 case per 10,000 per block. Filariasis: MDA with DEC + albendazole.
• Key indicators: API (malaria — elimination target <1 per 1000); Aedes larval indices: HI ≥1%, BI ≥5, CI ≥3% trigger dengue response; SPR ≥1% triggers enhanced malaria control.

REFLECT

You are posted as the medical officer at a primary health centre during the monsoon season. Your ASHA workers report a cluster of fever cases in a hamlet—some with rigor and chills (possibly malaria), some with joint pain and rash (possibly chikungunya or dengue). The local government school's overhead water tank was last cleaned 6 weeks ago and has visible larvae. The fields behind the hamlet are waterlogged with post-monsoon flooding. What is your systematic approach to the investigation? How would you decide which vector species to target first, and with which control measure? What are the reporting obligations under NVBDCP and IDSP? Reflect on the tension between rapid insecticide use (fast-acting but resistance-prone) and slower non-chemical approaches (sustainable but not immediately effective in an outbreak).