Definite host of toxoplasma:
**Core Concept**
Toxoplasma gondii is a protozoan parasite that causes toxoplasmosis, a zoonotic disease affecting humans and various animal species. The parasite has a complex life cycle involving multiple hosts, but it requires a specific definitive host for sexual reproduction.
**Why the Correct Answer is Right**
The definitive host of Toxoplasma gondii is a feline, particularly domestic cats (Felis catus) and their relatives. When an infected cat ingests oocysts, they undergo sporulation in the cat's intestine, leading to the production of tachyzoites, which then infect the cat's tissues. This process allows the parasite to complete its life cycle and reproduce sexually within the cat's body. The oocysts are then shed in the cat's feces, contaminating the environment and potentially infecting other hosts.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not specify a definitive host of Toxoplasma gondii. Humans can be intermediate hosts, but they are not the definitive host required for the parasite's sexual reproduction.
**Option B:** This option is incorrect because it is a common intermediate host of Toxoplasma gondii, but not the definitive host.
**Clinical Pearl / High-Yield Fact**
It's essential to note that while humans can be infected with Toxoplasma gondii, they act as intermediate hosts, and the parasite does not complete its life cycle within human tissues. This distinction is crucial for understanding the epidemiology and transmission dynamics of toxoplasmosis.
**Correct Answer:** D. Domestic cats (Felis catus) and their relatives.