The Medscape Awards in Infectious Diseases: Disease Most Likely to Be Eradicated From Earth

John G. Bartlett, MD

Disclosures

December 18, 2012

Infectious Disease Most Likely to Be the Second Eliminated From Earth

A 2-Horse Race

This is really a 2-horse race. The only serious candidates for "next" on the basis of priorities and progress are dracunculiasis and polio. Nevertheless, all of the candidates listed above are considered feasible, given adequate resources, political will, and popular support.

Dracunculiasis

The common name for dracunculiasis is "Guinea worm disease." It is caused by the parasite Dracunculus medinensis, and the name derives from the Latin for "a disease with little dragons." The term "Guinea worm" was applied when Europeans saw cases on the Guinea coast of West Africa in the 17th century.

Dracunculiasis is caused by ingestion of water that is contaminated by copepods carrying Guinea worm larvae. The end product is a worm that migrates painfully through the connective tissues, usually in the legs, from where it burrows toward the surface and forms a blister. The blister then bursts and the worm emerges, usually from the leg or foot. The pain from the burrowing through the skin is intense and is relieved by immersing the extremity in water, where the larvae are released to be ingested by copepods to complete the life cycle.

Prevention is achieved by eliminating copepods from drinking water sources, usually by filtering with a fine mesh, such as nylon. Alternatives are boiling the water, treating it with larvicides, or providing clean water from alternative sources, and educating villagers to avoid contaminating sources of drinking water when they have a worm emerging.

The emerging worm from the skin looks like a string of spaghetti. The disease is treated by rolling the worm on a stick or gauze over a period of weeks to months, taking care to avoid breakage (Figure 1).

Figure 1. Guinea worm in a Ghanaian patient. The worm is wound around a moist bandage during removal to prevent it from breaking. Courtesy of The Carter Center and L. Gubb

The international Guinea worm eradication campaign is spearheaded by The Carter Center, founded by former US President Jimmy Carter. The Center assumed leadership of the global program in 1986, after it was conceived and initiated by the CDC in 1980.

In 1986, an estimated 3.5 million cases occurred in 21 countries in Asia and Africa.[2] In 2011, cases numbered 1058, including 1028 in South Sudan (97% of all cases), 12 in Mali, 10 in Chad, and 8 in Ethiopia. In 2012, from January to October, a total of 536 cases occurred, mostly in South Sudan (516 cases); the remainder were in Chad (10 cases), Mali (7 cases), and Ethiopia (3 cases). Thus, the eradication program has reduced the disease burden by 99.9% and now concentrates on isolated pockets in just 4 countries, all in Africa (Table).

Table. Global Guinea Worm Disease Count

Year Total Cases Countries
1986 3,500,000 21
2011 1058 4

Guinea worm disease represents a unique challenge compared with other infections, in part because there is no vaccine or antibiotic. Furthermore, the public health methods used to prevent the disease must respect indigenous beliefs in affected areas. Village water supplies are often considered sacred, so applying chemicals is unacceptable. The method adopted by The Carter Center was one of the oldest and often the most difficult: a collaborative effort with extensive community involvement to filter the water, which leaves a legacy of community control.

This is an incredible record of achievement, but global disease eradication watchers warn that the big challenge is to get "the final inch": zero cases.[3] For Guinea worm disease, the primary persisting reservoir is South Sudan, which is one of the most difficult places for this public health work. Mali is a concern because of security issues in the endemic area after the coup d'état in March 2012.

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