Man is intermediate host for:
**Core Concept**
The question refers to the concept of intermediate hosts in the life cycle of parasites, particularly those causing malaria. An intermediate host is a host where the parasite undergoes a part of its life cycle before infecting the final host. In the context of malaria, the intermediate host is where the parasite undergoes asexual reproduction and multiplication.
**Why the Correct Answer is Right**
The correct answer is Plasmodium vivax. Plasmodium vivax is one of the four species of Plasmodium that cause malaria in humans. It has a unique life cycle that involves an intermediate host, typically the Anopheles mosquito, where it undergoes a part of its life cycle before infecting the human host. In humans, P. vivax undergoes asexual reproduction and multiplication in the liver cells, leading to the development of the disease.
**Why Each Wrong Option is Incorrect**
**Option A:** Plasmodium falciparum is the most virulent species of Plasmodium that causes malaria in humans. While it does infect humans, it does not require an intermediate host in its life cycle.
**Option B:** Toxoplasma gondii is a parasite that causes toxoplasmosis. It has a complex life cycle that involves cats as the definitive host and other mammals as intermediate hosts, but it is not related to malaria.
**Option C:** Leishmania donovani is a parasite that causes leishmaniasis. It has a life cycle that involves sandflies as the vector and humans as the host, but it does not require an intermediate host in the context of malaria.
**Clinical Pearl / High-Yield Fact**
It is essential to note that Plasmodium vivax can cause relapses due to the presence of hypnozoites, which are dormant stages of the parasite that can reactivate months or years after the initial infection.
**Correct Answer:** D. Plasmodium vivax.