**Core Concept:** Guinea worm disease, also known as dracunculiasis, is a parasitic infection caused by the larvae of the Dracunculus medinensis parasite. The infection occurs when humans drink contaminated water containing the intermediate host (Cyclops or copepods) that harbor the parasite larvae. In 1999, efforts to eradicate guinea worm disease through mass administration of diethylcarbamazine (DEC) and public health education led to a significant decrease in cases.

**Why the Correct Answer is Right:**

In 1999, the global number of guinea worm cases experienced a considerable decrease due to concerted efforts to eradicate the disease. One of the primary interventions was the mass administration of diethylcarbamazine (DEC), an antiparasitic medication. DEC is an effective treatment for dracunculiasis by targeting and killing the parasite larvae in humans and intermediate hosts. Additionally, public health education campaigns raised awareness about the infection's mode of transmission, promoting preventive measures such as the avoidance of drinking contaminated water.

**Why Each Wrong Option is Incorrect:**

A. This option is incorrect because it does not reflect the actual number of cases in 1999. The correct answer (B) provides the actual number.
B. Although DEC is an antiparasitic medication, the correct answer (C) focuses on the actual number of cases in 1999, while DEC is only one part of the eradication strategy. DEC is used to treat the infection, but the decrease in cases is primarily due to the combined efforts of mass administration and public health education.
C. This option is incorrect because it does not mention the actual number of cases in 1999 or emphasize the eradication strategy involving mass administration and public health education.
D. This option is incorrect because it does not focus on the actual number of cases in 1999 or emphasize the eradication strategy involving mass administration and public health education.

**Clinical Pearl:**

The eradication of guinea worm disease is a successful example of a global public health initiative. By combining antiparasitic treatments like DEC with community-based education campaigns, it is possible to significantly reduce and eventually eliminate diseases caused by neglected tropical parasites. Collaborative efforts between governments, non-governmental organizations, and international aid organizations are essential in combating infectious diseases globally.