Roundworms—Dracunculus medinensis and D. insignis cause Dracunculiasis

An adult worm releases larvae into a water source which are ingested by Cyclops (common in lakes). The animal or human ingest the water and the larvae develop into adult worms. A little blister erupts, usually in the lower extremities and is accompanied by fever, nausea, diarrhea and generalized itching before more blisters break out. Sepsis is common. Sometimes you can see the worm move in the lesion. Gross. 

Most cases of Dracunculus are in Africa and India but there have been a few cases in the eastern United States in dogs, wild carnivores and raccoons. Most animals can harbor the parasite. 

Treatment of Drancunculus includes niridazole and diethylcarbamazine. Um. . .I won’t describe how you get the worm out of the body. Google it. It’s gross!  The right picture shows a worm poking its head out of the lump. Ewww.  Don’t swim in dirty water—especially in foreign countries! 

Reference:

https://www.dpd.cdc.gov/dpdx/HTML/Dracunculiasis.htm