The secondary host of an organism refers to the host in which a parasite undergoes a necessary developmental stage before it can infect its final host. For example, some parasites may require a secondary host such as a water snail, in addition to their primary host, such as a human, in order to complete their life cycle. The parasite may enter the secondary host as a larva or immature form, and then develop into a form that can infect the final host once it is ingested. In this case, the answer would be Water Snail as it serves as the secondary host for certain parasites.
