The side effects from the medicine can also be nasty: Ivermectin may cause fever, itching, skin rash, joint or muscle pain, rapid heartbeat, and painful, tender glands.

CNN: With river blindness, 'you never sleep'

Serious adverse events also occurred more often in the niacin group, including new onset diabetes (9.1 vs. 7.3 percent), diabetic complications (11.1 vs. 7.5 percent), gastrointestinal problems (4.8 vs. 3.8 percent), and skin problems such as itching and rashes (0.7 vs. 0.4 percent).

FORBES: HPS2-THRIVE: A 'Disappointing But Clear' Result

The hallmark of eczema is itching with the skin scaling, crusting and an oozing of a serous or transparent fluid.

CNN: Does eating gluten cause eczema?

The worm can also cause severe itching under the skin, and it is hoped that cases can be reduced to only a fraction of previous levels.

BBC: Danger worms tracked from space