Concerning the vectors and transmission dynamics of malaria in India, all of the following are CORRECT EXCEPT:

Question

Accepted Answer

A. The extrinsic incubation period of Plasmodium parasites in the mosquito is temperature-independent and remains constant at 10–14 days regardless of ambient temperature. ## Malaria Vector Biology and Transmission Dynamics

### Extrinsic Incubation Period (EIP)

**Key Point:** The extrinsic incubation period (EIP) is **TEMPERATURE-DEPENDENT**, not constant. This is a critical concept in malaria epidemiology.

### Temperature Dependency of EIP

$$	ext{EIP} \propto \frac{1}{	ext{Temperature (°C)}}$$

| Temperature (°C) | EIP for *P. vivax* | EIP for *P. falciparum* |
|------------------|-------------------|------------------------|
| 20 | ~40 days | ~56 days |
| 25 | ~14 days | ~18 days |
| 30 | ~10 days | ~12 days |
| 35 | ~8 days | ~10 days |

**High-Yield:** Lower ambient temperature prolongs EIP; higher temperature shortens it. This is why malaria transmission is faster in hot, humid climates and slower (or absent) in cool regions.

### Correct Vector Characteristics

| Vector | Habitat | Behavior | Geographic Range |
|--------|---------|----------|------------------|
| *An. stephensi* | Clean, stagnant water (urban, semi-urban) | Anthropophilic, endophilic | Urban areas, cities |
| *An. fluviatilis* | Fast-flowing hill streams | Anthropophilic, exophilic | Foothills (Himalayas, Western Ghats) |
| *An. dirus* | Forest streams, shaded habitats | Zoophilic (partially), exophilic | Northeast India, forested terrain |
| *An. culicifacies* | Stagnant water (plains, plateaus) | Anthropophilic | Plains, Deccan plateau |

### Why the Incorrect Statement is Wrong

**Clinical Pearl:** The statement claiming EIP is "temperature-independent and constant at 10–14 days" is fundamentally incorrect. The 10–14 day range applies only at **optimal temperature (~25–30°C)**. At lower temperatures (15–20°C), EIP can extend to 40+ days; at higher temperatures (30–35°C), it shortens to 8–10 days. This temperature sensitivity is why malaria transmission is seasonal in temperate regions and perennial in tropical zones.

### Mnemonic

**"HEAT = FAST"** — Higher temperature → shorter EIP → faster transmission cycle → higher risk of epidemics in summer/monsoon.

Answer

B. Anopheles fluviatilis is anthropophilic, breeds in fast-flowing hill streams, and is the primary vector in foothill regions of the Himalayas and Western Ghats

Answer

C. Anopheles stephensi breeds in clean, stagnant water in urban and semi-urban areas and is an efficient vector of urban malaria

Answer

D. Anopheles dirus is a forest-dwelling vector found in the Northeast India and is responsible for transmission in forested and hilly terrain

Concerning the vectors and transmission dynamics of malaria in India, all of the following are CORRECT EXCEPT:

Explanation

Practice similar questions