Final answer:
The definitive host of Toxoplasma gondii is the house cat, which plays a unique role in the life cycle by hosting the sexual reproduction stage of the parasite. Other animals, including dogs, chickens, and rodents, act as intermediate hosts.
Step-by-step explanation:
The definitive host of Toxoplasma gondii is the house cat. A definitive host is where the parasite reaches maturity and, in the case of sexually reproducing parasites, hosts the sexual reproduction stage. In terms of Toxoplasma gondii, domestic cats are the only known definitive hosts for the sexual stages of this protozoan. Humans and other mammals, including dogs, rodents, and even birds, can serve as intermediate hosts, where the parasites form cysts in the muscle and neural tissues but do not reproduce sexually. Infected cats shed T. gondii oocysts in their feces, which can infect intermediate hosts when they come into contact with these oocysts in the environment, such as through contaminated soil, water, or ingestion of undercooked meat.
The life cycle of Toxoplasma gondii is quite complex, involving multiple hosts and stages of development. The prevalence of Toxoplasma infection in humans can be significant, and while most people with a healthy immune system are asymptomatic, it can cause serious complications in immunocompromised individuals and during pregnancy. Interestingly, Toxoplasma infection can also influence the behavior of infected intermediate hosts, such as rodents, which lose their innate aversion to cats, potentially increasing transmission rates.