Excerpt from Dracunculiasis

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Background

Dracunculiasis is an infection caused by the nematode Dracunculus medinensis, also known as the guinea fire worm. D medinensis is in the order Spirurida, an order of parasites that includes the filariae Wuchereria bancrofti, Brugia malayi, and Loa loa. During the last 25 years, concerted efforts to eradicate the guinea worm have been undertaken and these have resulted in a reduction of more than 99% of worldwide cases of dracunculiasis.

Current disease incidence is low and is limited specifically to sub-Saharan Africa. The Centers for Disease Control and Prevention (CDC) proposed a global campaign for eradication of dracunculiasis in 1980, and, in 1988, a number of African ministers of health set a target date of 1995 for total eradication. Although several factors have prevented accomplishment of this goal, the CDC now projects that the disease may be completely eliminated by 2009. This will mark an important epidemiologic medical accomplishment, as well as the end of a fascinating organism.

During ancient times, the presence of dracunculiasis can be inferred by the universally recognized symbol of medicine, the Greek asklepios (ie, Roman aesculapius), which consists of a one-headed snake wrapped around a stick. Dead female worms have also been found in Egyptian mummies older than 3000 years, and writings in ancient Sanskrit, Greek, and Hebrew refer to Dracunculus infection. To this day, the most effective method dracunculiasis treatment involves extraction by wrapping the worm around a stick. The term dracunculus is Latin for "little dragon," a misnomer and reference to the symbol. Thus, when the guinea worm disappears, one of the original inspirations for the discipline of medicine will also disappear. Currently, the infection persists and, although uncommon, can cause significant morbidity.

Pathophysiology

Ingestion of water that contains infective Dracunculus larvae causes the infection. The larvae reside in an intermediate host, a tiny fresh-water crustacean or copepod of the genus Cyclops. The acidic environment of the stomach and duodenum kills the copepods. The larvae are subsequently released in the stomach or small intestine and penetrate the mucosa to mate and mature in the abdomen or retroperitoneal space approximately 60-90 days after initial infection. The maturation stage can last for up to 1 year, and, during this time, the adult male probably dies because only the female worm is recovered from symptomatic patients.

After maturation is complete, the female Dracunculus reaches a length of up to 1 m (with a thickness of only 1-2 mm) and slowly migrates from the GI tract into subcutaneous tissue, usually to a location in the lower extremity. The actual route of migration is unknown. In this subcutaneous location, one or more females prepare larval exit sites through the skin, from whence larvae may be released into another water supply. Free-living larvae can survive only 3 days without a host; they become infective after 2 weeks (2 molts) within the host copepod.

Frequency

United States

Dracunculiasis is rarely imported to the United States. Two cases have been reported since 1995, both occurring in individuals from Sudan.

International

In the early 1990s, 3-5 million cases of dracunculiasis occurred worldwide each year. By 1996, only 152,805 cases were reported, most from Ghana and Sudan. Presently, only 9 countries are endemic: Sudan, Ghana, Nigeria, Mali, Togo, Burkina Faso, Ethiopia, Niger, and Ivory Coast. Recent statistics indicate that only 8,191 cases were reported during the first half of 2005 from these 9 nations. At the end of 2004, all of Asia was free of the disease. Sporadic cases have been noted in Australia and North America in African immigrants.

Mortality/Morbidity

Death due to dracunculiasis is not caused by the primary infection and occurs only in cases in which secondary infection of the worm's exit site leads to sepsis. The mortality rate is quite low; however, morbidity is a major concern, with secondary infection being the most common complication. Cellulitis or the formation of an abscess requires prompt attention, and pain from the exit sites often can incapacitate patients for weeks. This is usually observed in individuals who have multiple worms and rely on their ability to stand or walk for their livelihood. Farmers with untreated dracunculiasis in Nigeria have been found to miss work for up to 3 months. Infected schoolchildren may miss up to 25% of the school year. Therefore, Dracunculus infection can cause significant socioeconomic burden for individuals and communities.

Another, more chronic, complication of dracunculiasis is encapsulation of the adult worm, which occurs when the calcified remains of the worm persist in the extremity of the patient. This can result in chronic pain and intermittent swelling of the extremity. In a small percentage of individuals who have permanent scarring or deformity of the lower extremity, even after the worm has been extracted, chronic pain may persist for up to 18 months. Notably, on average, infected individuals have multiple worm extrusions at the same time (1.8 worms per person, on average). Rarely, dracunculiasis can present with worms located in anomalous locations, including the lungs, pancreas, testes, spinal cord, or periorbital tissue.

Race

No race predilection exists.

Sex

No sex predilection exists.

Age

Most reported dracunculiasis cases occur in the young adult (working) population who may be exposed to contaminated water sources more frequently; however, no particular age predilection exists.

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