The definitive host for echinococcus granulosus is-
**Core Concept**
Echinococcus granulosus is a parasitic tapeworm that causes cystic echinococcosis (also known as hydatid disease). The definitive host is the organism in which the parasite reaches maturity and reproduces sexually.
**Why the Correct Answer is Right**
The definitive host for E. granulosus is the dog (Canis lupus familiaris). Adult worms reside in the small intestine of dogs, where they attach to the mucosa and reproduce, producing eggs that are shed in the host's feces. These eggs contain the infective larval stage, which is ingested by intermediate hosts (such as sheep, cattle, or humans), leading to the development of hydatid cysts.
**Why Each Wrong Option is Incorrect**
**Option A:** Sheep are intermediate hosts for E. granulosus, not definitive hosts.
**Option B:** Humans can be infected with E. granulosus but are not the definitive host; they are intermediate hosts.
**Option C:** Cattle can also be intermediate hosts for E. granulosis.
**Clinical Pearl / High-Yield Fact**
It's essential to note that dogs are the primary definitive hosts for E. granulosus, and controlling the parasite's lifecycle in dogs is crucial for preventing the spread of cystic echinococcosis in humans and other animals.
**Correct Answer: C. Dogs.**