30 yrs old farmer treated initially with chloroquine for uncomplicated malaria now has an episode of relapse, what could be the reason for relapse?
**Core Concept**
The question is testing knowledge of the mechanism of action of chloroquine and the phenomenon of chloroquine-resistant malaria. Chloroquine is a 4-aminoquinoline antimalarial drug that acts by inhibiting the parasite's heme detoxification pathway in the food vacuole of Plasmodium species.
**Why the Correct Answer is Right**
The correct answer is related to the mechanism of resistance to chloroquine in Plasmodium falciparum. Chloroquine-resistant strains of P. falciparum have a point mutation in the gene encoding the parasite's chloroquine resistance transporter (PfCRT), which leads to a change in the protein's structure and function. This mutation reduces the accumulation of chloroquine in the parasite's food vacuole, allowing the parasite to survive and multiply despite the presence of the drug. As a result, the parasite can cause a relapse of malaria.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is not relevant to the mechanism of resistance to chloroquine in malaria.
* **Option B:** This option is incorrect because the correct answer is related to the specific mechanism of resistance to chloroquine, not the general concept of drug resistance in malaria.
* **Option C:** This option is incorrect because the correct answer is related to the specific mechanism of resistance to chloroquine, not the general concept of parasite biology.
**Clinical Pearl / High-Yield Fact**
It's essential to note that the emergence of chloroquine-resistant strains of P. falciparum has led to the increased use of alternative antimalarial drugs, such as artemisinin-based combination therapies (ACTs). These drugs have a higher efficacy against chloroquine-resistant strains and are now recommended as first-line treatment for uncomplicated malaria in many parts of the world.
**Correct Answer:** C.