"The clinical manifestations are localized but very incapacitating. 

The worm emerges as a whitish filament (duration of emergence: 1 to 3 weeks) in the center of a painful ulcer, accompanied by inflammation and frequently by secondary bacterial infection.

 In endemic countries, the annual incapacitation of a substantial proportion of the population, at a period of intense agricultural activity, has serious economic consequences."

Courtesy of the Division of Parasitic Diseases at the National Center for Infectious Diseases, Centers for Disease Control and Prevention

"The female guinea worm induces a painful blister (A); after rupture of the blister, the worm emerges as a whitish filament (B) in the center of a painful ulcer which is often secondarily infected.  (Images contributed by Global 2000/The Carter Center, Atlanta, Georgia)."

Courtesy of the Division of Parasitic Diseases at the National Center for Infectious Diseases, Centers for Disease Control & Prevention