Echinococcus granulosus are commonly seen in which of the given animals:
**Core Concept**
Echinococcus granulosus is a parasitic tapeworm that causes cystic echinococcosis (also known as hydatid disease) in humans. This tapeworm has a complex life cycle involving intermediate and definitive hosts, with a specific preference for certain animals.
**Why the Correct Answer is Right**
The correct answer involves understanding the life cycle of Echinococcus granulosus. The definitive hosts of E. granulosus are canines, such as dogs, wolves, and foxes, which harbor the adult tapeworms in their small intestines. The intermediate hosts, on the other hand, are herbivores whose feces contaminate the environment, potentially infecting other animals and humans through accidental ingestion of the parasite. Sheep, goats, and cattle are common intermediate hosts.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because, although rabbits can be infected with E. granulosus, they are not the primary intermediate hosts.
**Option B:** This option is incorrect because cats are not typically involved in the life cycle of E. granulosus. While cats can occasionally harbor the parasite, they are not the primary definitive hosts.
**Option C:** This option is incorrect because horses are not commonly associated with E. granulosus infection.
**Clinical Pearl / High-Yield Fact**
Echinococcus granulosus is a zoonotic parasite, meaning it can be transmitted from animals to humans. Accidental ingestion of the parasite through contaminated feces or contaminated food and water can lead to cystic echinococcosis in humans.
**Correct Answer: D. Sheep, goats, and cattle are common intermediate hosts.**