## **Core Concept**
The question tests knowledge of parasitic diseases and their modes of transmission, specifically focusing on those that involve egg ingestion as a critical step in their lifecycle.

## **Why the Correct Answer is Right**
Dicrocoeliosis, caused by *Dicrocoelium dendriticum*, is a parasitic infection that indeed involves ingestion of eggs as part of its lifecycle. The eggs are shed in the feces of infected definitive hosts (usually cattle) and are ingested by ants, the intermediate hosts. Humans can become infected by ingesting eggs from contaminated food or water, but more commonly, the lifecycle involves grazing animals. This highlights a unique aspect of its transmission.

## **Why Each Wrong Option is Incorrect**
- **Option A:** While *Taenia saginata* (beef tapeworm) does involve ingestion of cysticerci (larval stages) in undercooked beef, it does not primarily involve egg ingestion for its transmission to humans.
- **Option B:** *Toxoplasma gondii* is primarily transmitted through oocysts in cat feces or undercooked meat, not through egg ingestion.
- **Option C:** *Echinococcus granulosus* causes cystic echinococcosis and is transmitted through ingestion of eggs shed by the definitive host (usually dogs), but the question seems to focus on a disease where egg ingestion directly leads to a commonly recognized infection pattern.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that *Dicrocoelium dendriticum*, also known as the lancet liver fluke, has a complex lifecycle involving ants as intermediate hosts and typically infects grazing animals. Human infections are rare but can occur through accidental ingestion of infected ants.

## **Correct Answer:** D. Dicrocoeliosis