Dracunculosis (also known as dracunculiasis or guinea worm) is caused by the helminth Dracunculus medinensis. It will probably be the second infection to be eradicated from the world. Known as the guinea worm, it is currently endemic to only 4 countries in Sub-Saharan Africa: Chad, Ethiopia, Mali, and South Sudan.

The human host becomes infected after drinking water containing copepods (water fleas), which in turn harbor the larvae. The larvae mate, and pregnant females travel systemically until reaching the subcutaneous tissue of the lower extremity, where they can grow to one meter in length. They then create a portal of exit where the worm can be visualized. The female worm expels her pre-larvae over water (sensed by a drop in temperature) to complete the cycle. She continues to expel her pre-larvae for several weeks until she finally emerges fully a few weeks later.

Individuals who harvest crops or collect water are typically at highest risk for contracting dracunculosis. Human and canine cases in Chad have been associated with the fishing industry and are thought to have been caused by consumption of undercooked or raw fish.

Dracunculosis is rarely seen in US clinics. The last 2 cases were both immigrants from Sudan.