In which host does sexual reproduction of a parasite take place?

The definitive host is where the adult stage of a parasite is found and where sexual reproduction takes place. In the life cycle of many parasites, particularly helminths and protozoa, the definitive host is crucial as it is the organism in which the mature form of the parasite resides and reproduces sexually, leading to the production of offspring, usually in the form of eggs or larvae.

In contrast, the intermediate host is where asexual reproduction often occurs. For many parasites, this stage allows for the development and multiplication of the larval stage before moving to the definitive host, where sexual phase and maturation take place. Asexual reproduction can also occur in various other stages or forms of the parasite life cycle.

Vector organisms typically act as a means of transmission for the parasite, facilitating its movement from one host to another, but they are not the hosts in which the parasite undergoes sexual reproduction. Thus, the definitive host is specifically recognized for its role in allowing the parasite to engage in sexual reproduction, which is essential for the continuation of its life cycle.