Question

Which of the following is a definitive host of the liver fluke?

• A. Snail
• B. Fish
• C. Human
• D. All of the above

Answer 1

The correct option is A Snail

Parasitism is a type of population interaction between two living species in which one organism is benefited (+) at the expense of the other (-). The organism that is benefitted is called the parasite, while the one that is harmed is called the host.

Host are of two types:

• Definitive hosts are organisms that supports the adult form of the parasite. It is also the site of sexual reproduction of the parasite.
• Intermediate hosts are organisms that support the larval stages of parasites. These are the asexual forms of the parasite.

The human liver fluke (Fasciola hepatica) is an endoparasitic (lives inside the host body) worm that lives in the liver of humans and causes disease.
Humans harbors the adult parasite (liver fluke) in the body. The parasite reproduces sexually in human. Therefore, human is the definitive or primary host for the liver fluke.
The snail or fish harbors the larval stage or the asexual forms of the parasite. Therefore, they are intermediate or secondary host of liver fluke.