Dracunculiasis is caused by the ___________ worm and transmitted by the __________ vector

The correct option is Dracunculus medinensis; freshwater crustacean.

Step-by-Step Explanation:

1. Identifying the causative agent:
Dracunculiasis, commonly known as Guinea worm disease, is a parasitic infection. It is caused by the nematode (roundworm) parasite named Dracunculus medinensis. In contrast, Mycobacterium ulcerans is a bacterium that causes Buruli ulcer, not dracunculiasis.

2. Identifying the transmission vector/host:
The infection is transmitted to humans when they drink stagnant water contaminated with microscopic freshwater crustaceans (specifically copepods, also known as water fleas) belonging to the genus Cyclops. These copepods act as the intermediate hosts harboring the infective Guinea worm larvae.

3. Conclusion:
Combining these two facts, Dracunculiasis is caused by the worm Dracunculus medinensis and transmitted by a freshwater crustacean vector, making the correct option Dracunculus medinensis; freshwater crustacean.