No. 25: Elimination of guinea worm disease (dracunculiasis) by the year 2000

The Challenge:

In a dwindling number of countries, guinea worm surfaces each year during the agricultural season in impoverished rural villages dependent on unsafe water, bringing months of crippling pain to those affected, leaving its adult victims unable to till the fields or tend their children and its child victims unable to attend school or go for immunization. 

Please click here to view the transmission cycle of the Guinea worm 

Dracunculus medinensis is the largest of the tissue parasites affecting humans, in villages where stagnant ponds or shallow unprotected wells are the only source of water. The adult female guinea worm, up to a meter long and 2 mm across, carries 1-3 million embryos. It migrates through its victim's body and eventually perforates the skin, usually at the ankles or feet, causing intensely painful swelling, blistering and ulceration where it emerges. Whenever an infected person steps into water the worm expels thousands of its embryos, a process that continues for up to three weeks.

The embryos are preyed on by cyclops, a tiny water crustacean that serves as the intermediate host for the embryos to grow to infectious larvae. When humans drink water containing infected cyclops, the larvae settle in the intestine to mature and mate. The embryo-laden females start their migration a year after the infected water was consumed. If their embryos are again released into water containing cyclops and again used for drinking, the cycle starts up again.

The Impact:

Although the worms release their embryos and die within three weeks, sufferers often remain incapacitated for several months by the complications - infection by more than one worm at a time; worms emerging in especially sensitive areas such as the soles of the feet; serious bacterial infection if a worm is accidentally ruptured; and further infection if a dead worm is not carefully extracted.

No drugs exist to prevent or heal infection. The suffering can only be alleviated, by analgesics to reduce the pain and inflammation and by antibiotic ointment to ward off bacteria. The worm's emergence can be speeded up by cautiously winding it onto a stick, a few centimeters a day.

Breaking the cycle:

Simple preventive measures can interrupt and eventually end transmission:

• Educating all village households to filter cyclops from their drinking water using fine-mesh cloth or preferably a nylon fine-mesh filter (boiling the water is also effective but impractical where fuel is scarce;

• Prevent people with emerging worms from entering the water sources to break the live cycle of the worm;

• Drilling borehole wells fitted with pumps, and constructing copings around unprotected wellheads;

• In some cases, treating surface waters with a chemical toxic to the worm larvae but not humans.

Improving wells to provide safe water  not only protects against diarrhoeal infections but also against guinea worm - a cost- effective proposition in Sub-Saharan Africa, where three out of five country dwellers still have to rely on unsafe water sources.