Anopheles Mosquito
Anopheles stephensi
📖 Description
Anopheles mosquitoes are the sole vectors of human malaria — a disease that kills ~600,000 people globally each year, the vast majority being African children under 5. India has made remarkable progress in malaria control: from ~75 million cases and 800,000 deaths at independence in 1947 to ~17,000 cases and ~30 deaths in 2023 — a 99.97 % reduction in cases over 75 years, achieved through the National Malaria Control Programme (1953), National Malaria Eradication Programme (1958), and the current National Framework for Malaria Elimination (2016) targeting elimination by 2030. India is now in the pre-elimination phase and the World Health Organization has certified that 124 of India’s 729 districts have achieved zero indigenous cases for three consecutive years. The Anopheles genus contains ~460 species worldwide, but only ~70 transmit human malaria. India has 58 Anopheles species, of which 6 are major malaria vectors — Anopheles culicifacies (rural, ~65 % of Indian malaria transmission), An. stephensi (urban, ~15 %), An. fluviatilis (foothill), An. minimus (North-East hills), An. dirus (forested North-East), and An. sundaicus (Andaman & Nicobar coastal). Agricultural environments are critically important breeding sites: An. culicifacies breeds prolifically in paddy fields, irrigation canals, and rainwater puddles, making rice-growing belts disproportionately high-risk for malaria. The link between rice cultivation and malaria is so well-established that the Indian Council of Medical Research (ICMR) has developed ‘agro-eco-system-based malaria control’ guidelines specifically for rice-growing districts of Odisha, Chhattisgarh, Jharkhand, and the North-Eastern states. Climate change is shifting malaria transmission zones; An. stephensi has recently invaded the Horn of Africa and is causing urban malaria outbreaks in Ethiopia, Djibouti, and Sudan — a worrying global trend.
⚠️ Symptoms to watch for
- Adult female bite causes itchy raised wheal on human skin. Disease transmission: Anopheles is the sole vector of human malaria — India reported ~17,000 malaria cases in 2023 (down from ~2 million cases in 2000, due to India's successful National Malaria Elimination Programme targeting elimination by 2030). Anopheles stephensi is the principal urban malaria vector in India; Anopheles culicifacies is the principal rural vector. Agricultural relevance: paddy fields and irrigation infrastructure are the principal breeding habitat of An. culicifacies in rural India, making rice-growing belts disproportionately high-risk for malaria.
🩹 Treatment
- Larval source management: apply Abate (temephos) 50 EC at 1 ml/100 L in large water bodies; alternatively apply Paris Green (copper acetoarsenite) at 1 kg/ha as a surface dust — the particles float and kill surface-breathing larvae. Biological: release larvivorous fish (Gambusia affinis, Poecilia reticulata, Aplocheilus panchax) in ponds and tanks — each fish eats 100+ larvae per day. Adult control: indoor residual spraying (IRS) of DDT 50 % WP (in residual foci) or lambda-cyhalothrin 10 CS at 25 mg a.i./m² in high-transmission areas; mass distribution of long-lasting insecticidal nets (LLINs).
🌿 Organic treatments
- Larvivorous fish (Gambusia affinis — mosquitofish, Poecilia reticulata — guppy, Aplocheilus panchax — Indian killifish) in ponds, tanks, and rice fields (the most cost-effective biological control — ~₹1 per fish, each fish eats 100+ larvae/day); application of Bacillus thuringiensis var. israelensis (Bti) at 1 g/100 L in storage containers; application of neem oil 0.5 % on water surface; intermittent irrigation of paddy fields (alternate wetting and drying — breaks the larval lifecycle); use of long-lasting insecticidal nets (LLINs) over beds; planting of mosquito-repellent herbs around the house.
🧪 Chemical treatments
- Temephos 50 EC @ 1 ml/100 L (larvicide); Lambda-cyhalothrin 10 CS @ 25 mg a.i./m² (indoor residual spray); Deltamethrin 2.5 % WP @ 12.5 mg a.i./m² (IRS); DDT 50 % WP @ 1–2 g/m² (IRS — restricted to residual malaria foci in the North-East); Artemisinin-based Combination Therapy (ACT) for case management. Pyrethroid resistance is now widespread in Indian An. culicifacies; rotate chemical groups.
🛡️ Prevention
- Cover all water storage containers with tight-fitting lids; eliminate standing water in discarded tyres, flower pots, and gutters; use intermittent irrigation in paddy fields (alternate wetting and drying every 7–10 days — breaks the larval lifecycle); install mosquito-proof screens on windows and doors; use long-lasting insecticidal nets (LLINs) over beds — the single most effective malaria prevention tool; wear long-sleeved clothing and apply DEET-based repellent (20–30 %) during dusk-to-dawn biting hours; pregnant women and young children should sleep under LLINs every night.
🪴 Affected plants
- No direct plant host. Breeds in a wide range of freshwater habitats including paddy fields, irrigation canals, rainwater puddles, slow-moving streams, ponds, and (for the urban-adapted Anopheles stephensi) water storage containers, cisterns, and overhead tanks.
🦋 Natural predators
- Larvivorous fish (Gambusia affinis, Poecilia reticulata, Aplocheilus panchax, Channa spp. — snakeheads), dragonfly and damselfly nymphs, predatory copepods, Toxorhynchites mosquito larvae, water beetles (Dytiscidae), backswimmers (Notonectidae), spiders, and insectivorous birds (swallows, martins).
🌱 Host plants
- No plant host — the mosquito does not feed on plants. An. culicifacies breeds prolifically in paddy fields (Oryza sativa), irrigation canals, and rainwater puddles in agricultural landscapes, making rice-growing belts disproportionately high-risk for malaria.
🔄 Lifecycle
- Adult female lays 100–250 boat-shaped eggs singly on the water surface, each egg equipped with lateral air-filled floats; eggs hatch in 2–4 days (no egg desiccation resistance, unlike Aedes).
- Larva passes through 4 instars over 7–14 days, lying flat at the water surface.
- Pupa is comma-shaped and aquatic, non-feeding, stage 1–3 days.
- Adult emerges at the water surface; female takes her first blood meal 2–3 days later.
- Female longevity 14–30 days; male 7–14 days.
- Total lifecycle (egg to adult) 10–20 days; 4–8 overlapping generations per year depending on temperature.
📅 Season
- Peak abundance during the monsoon and post-monsoon season (July–November) when standing water is abundant.
- Population crashes during the dry hot season (April–June).
- In irrigated rice-growing belts, the active season extends year-round wherever paddy is grown.
🔎 Appearance
- Adult is a pale brown mosquito with dark spots on the wings (the 'spotted-wing' appearance diagnostic of Anopheles); at rest the body is held at a steep 30–45° angle to the surface (the 'tail-up' posture that distinguishes Anopheles from Aedes and Culex, which hold the body parallel).
- Larva is aquatic, lying flat at the water surface (parallel to the surface, not head-down like Aedes) and lacks a siphon tube — it breathes through spiracles on the abdomen directly at the surface.
- Pupa is comma-shaped and aquatic.
💥 Damage level
- Severe
🔁 Reproduction rate
- Fast
🗺️ Geographic regions
- Cosmopolitan in tropical
- subtropical
- and warm temperate regions globally; in India — all states and union territories
- with the highest malaria burden in Odisha
- Chhattisgarh
- Jharkhand
- Meghalaya
- Mizoram
- and Arunachal Pradesh (which together account for ~80 % of Indian cases). Anopheles stephensi is native to South Asia and the Middle East; recently invaded the Horn of Africa.
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