Dracunculiasis (guinea Worm Disease): Case Study of the Effort to Eradicate Guinea Worm

Dracunculiasis (Guinea worm disease) is a water-borne parasitic infection that is intimately tied to the environment and to human behavior. The campaign to eradicate this disease lasted nearly 30 years and provides many lessons that may be adapted for attacking other problems successfully, particularly where change in human habits is required in order to mitigate or interrupt transmission. The adult parasiteDracunculus medinensis occurs only in humans, who become infected after drinking stagnant surface water from sources such as ponds where microscopic water fleas (copepods) have been infected by ingesting immature forms of the parasite. The parasite matures in humans over a period of 1 year, during which the infection evokes no symptoms or outward signs. After a year, the thin white adult worm, which measures up to 3 feet (1m) long, emerges slowly and painfully through a ruptured blister that it raises on the skin (Fig. 10.1). Most worms emerge on the leg, ankle, or foot, but they may emerge from anywhere on the body, and a patient may have up to a dozen or more worms emerge around the same time. The emerging adult worms are all females, which spew hundreds of thousands of immature larvae into the water when the infected person enters a surface source such as a pond for any reason. Thus, the life cycle of the worm is perpetuated by humans who drink untreated water from such contaminated sources, as well as by those who enter sources of drinking water while a Guinea worm is emerging or about to emerge from their body. Since only a few centimeters of a worm can usually be pulled out manually by rolling it on a small stick or rolled gauze in a day, the painful incapacitation associated with this infection normally lasts up to 1 or 2 months or more. The site of worm emergence often becomes infected secondarily with various bacteria, increasing the local inflammation and pain that are the hallmarks of this disease. Infection with tetanus bacilli at the site of the ulcer, which is the base of the ruptured blister caused by the emerging worm, is the most dangerous secondary complication of Guinea worm disease, which otherwise is not usually fatal. In about one-half of 1% of cases, aworm that emerges in or near amajor joint such as the elbow or knee can cause permanent freezing of that joint, with consequences very similar to crippling damage from paralytic poliomyelitis. Past infections do not confer immunity, so people can be reinfected year after year. There is no animal or any other environmental reservoir of D. medinensis outside of human beings and the infection has been recognized in ancient sources such as Egyptian mummies and the Old Testament. The immature larvae last only a few weeks outside of the human body, and only if they are ingested by a copepod. That is why this disease is vulnerable to complete eradication, even though copepods are ubiquitous in stagnant surface sources of freshwater. The impact of Guinea worm disease on affected communities can be devastating, even though the infection is not usually fatal. This is a disease of remote, neglected rural populations that do not have easy access to clean drinking water. Before the eradication campaign began, up to 50% or more of a village’s population could be infected at the same time, for periods averaging 1–2 months. Working age adults of both sexes are affected most of all because they tend to drink larger volumes of water. And the worms emerge