**Core Concept**
Guinea worm infestation is caused by the parasite *Dracunculus medinensis*, which is transmitted through contaminated water containing copepods (water fleas) infected with the parasite's larvae. The parasite's lifecycle involves the ingestion of these copepods by humans, leading to the development of adult worms in the human host.

**Why the Correct Answer is Right**
The correct answer involves occupational exposure to contaminated water sources, which is common among workers in certain industries, such as fishing or water supply management. When these workers handle or consume contaminated water, they may ingest the copepods harboring the Guinea worm larvae, leading to infection. The parasite then migrates through the host's body, eventually emerging through the skin, causing severe pain and blistering.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is not relevant to Guinea worm infestation, as it is not associated with a specific occupational group.
**Option B:** While certain occupations may involve exposure to contaminated water, this option is too vague and does not specifically address the Guinea worm parasite.
**Option C:** This option is incorrect, as the Guinea worm parasite is not commonly associated with agricultural workers.

**Clinical Pearl / High-Yield Fact**
Guinea worm infestation is a significant public health concern in areas where access to clean water is limited, and the parasite's lifecycle involves a complex interaction between the parasite, copepods, and human hosts.

**Correct Answer: D. Fishermen and water supply workers are at increased risk of Guinea worm infestation due to their occupational exposure to contaminated water sources.**