**Question:** The following are DDT resistant except -

A. Anopheles gambiae
B. Anopheles funestus
C. Culex quinquefasciatus
D. Aedes aegypti

**Core Concept:** DDT resistance in mosquitoes

**Why the Correct Answer is Right:** DDT (Dichlorodiphenyltrichloroethane) is an insecticide that was widely used for malaria control in the past. Insects, including mosquitoes, evolved resistance to DDT over time. Out of the given options, Aedes aegypti is the only species not known to develop resistance to DDT due to its low levels of cytochrome P450 enzymes involved in DDT biotransformation.

**Why Each Wrong Option is Incorrect:**

A. Anopheles gambiae: This species is known to develop resistance to DDT due to increased expression of GST (Glutathione S-Transferase) and P450 enzymes, which lead to accelerated DDT biotransformation.

B. Anopheles funestus: This species has been reported to develop resistance to DDT through increased expression of P450 enzymes, similar to Anopheles gambiae.

C. Culex quinquefasciatus: This species is known to develop resistance to DDT due to increased expression of GST and P450 enzymes, similar to Anopheles gambiae and Anopheles funestus.

D. Aedes aegypti: As mentioned above, Aedes aegypti develops resistance to DDT due to low levels of cytochrome P450 enzymes involved in DDT biotransformation. This makes Aedes aegypti less likely to develop DDT resistance compared to other species.

**Core Concept:** Cytochrome P450 enzymes are crucial in biotransformation of DDT into less toxic compounds, leading to insecticide resistance.

**Core Concept:** Glutathione S-Transferase (GST) and P450 enzymes are involved in DDT biotransformation, leading to insecticide resistance in mosquitoes.

**Core Concept:** The World Health Organization (WHO) recommends using insecticide-treated bed nets and indoor residual spraying (IRS) as alternative strategies to control mosquito-borne diseases like malaria.

**Clinical Pearls:** Understanding insecticide resistance mechanisms in mosquitoes is crucial for public health strategies to combat mosquito-borne diseases like malaria. Employing alternative methods such as bed nets and indoor residual spraying can help combat such diseases effectively without relying solely on insecticides.