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A Social Issue Neglected Tropical Diseases and Three Major Infectious Diseases

Dracunculiasis (Guinea Worm Disease)

<Appearance of a patient infected with guinea worm > CDC

Dracunculiasis, commonly called guinea worm disease (GWD), is transmitted to humans when water fleas belonging to the genus Cyclops are infected with the larvae of the guinea worm, a type of helminth (parasitic worm), and subsequently enter the body through contaminated sources of drinking water. The larvae then mature inside the human host and, after copulation, induce a blister on the skin just above where the adult female is present (often on the lower leg). From this blister, the female worm will then begin to emerge in order to release larvae outside of the host body, causing a searing, burning sensation to the host. Currently, the number of reported cases is decreasing thanks to ongoing eradication efforts.

Causes of Infection

Disease Agent

Guinea worm, a parasitic helminth

< Larvae of guinea worm > CDC

Intermediate Host

Water fleas from the genus Cyclops

Water fleas infected with guinea worm larvae transmit the disease to humans via contaminated sources of drinking water. The larvae then mature within the body of the host, growing to as long as one meter in the space of 10–14 months. Once an adult female worm is ready to release larvae, it will migrate to areas just beneath the skin, inducing a blister accompanied by itching and pain.
 Guinea worms normally inhabit stagnant water such as puddles, ponds, water reservoirs and wells, but tend to be absent from rivers and other running water. Humans are more susceptible to guinea worm infection in arid regions where they drink stagnant water during the rainy season, or from puddles formed in swampland during the dry season when the water level is low.

Symptoms

Normally, no symptoms are observed for about a year from initial infection. Once an adult guinea worm is ready to release larvae, however, it will migrate to just below the skin’s surface, leaving one or more blisters visible on the skin.
At this stage, by cooling the blistered area in cold water, the worm will detect the difference in temperature and emerge from the body to release thousands of larvae. At this point, patients will experience a painful, burning sensation in the area of the blister. Permanent damage can also occur in cases of joint infections, which can cause the joints to lock and deform.
If a worm breaks during removal, the remaining part of the worm will start to degrade inside the body and this can lead to intense inflammation, including cellulitis. Furthermore, if the infection is not properly treated, it can result in other complications such as abscesses, sepsis and tetanus.

< Appearance of a patient infected with guinea worm > CDC

Diagnosis and Treatment

Diagnosis is made by the visual inspection of adult worms in blisters on the skin.
Currently, there is no effective drug used for the treatment of guinea worm infection. The only existing treatment is to remove adult worms by applying traction to slowly pull them out from the body once they emerge from beneath the skin. Full extraction of the worm can take from several days to weeks.

Prevention

Currently, there is no effective vaccine to prevent guinea worm infection, nor will prior infection provide immunity against the disease.
The most effective preventive measure against guinea worm infection is ensuring access to safe drinking water, thereby preventing ingestion of infected water fleas. Concrete measures include using cloth and pipe filters for drinking water and applying an approved larvacide to contaminated drinking-water sources, such as in small ponds or open wells. Another precaution is to ascertain that patients with the disease are kept away from shared sources of drinking water.

Regions at High Risk of Infection

The infection risk is high in areas remote from urban centers in Africa where safe drinking water is hard to come by. According to data released by the World Health Organization (WHO) in 2016, infections were reported in only four countries, namely, Chad, Ethiopia, Mali, and South Sudan, with 41% of cases occurring in Chad.

Estimated Number of Infected People

The number of infected people has declined every year since 1986 due to a successful campaign to eliminate infection. According to data released from CDC, 22 people had been infected worldwide in 2015, hinting that complete eradication of the disease worldwide is possible in the near future.

Estimated Number of Deaths

Although the death rate is low, disability is a common outcome of guinea worm disease. Patients often have difficulty moving around because of pain as well as complications from secondary bacterial infections. While disability normally lasts 8.5 weeks on average, it can sometimes be permanent.

Initiatives by Pharmaceutical Companies and NGOs

The World Health Assembly (WHA) launched a program to eradicate guinea worm disease in 1986. The fight for eradication of the disease was later joined by the Carter Center (founded by former U.S. President Jimmy Carter), UNICEF, CDC and many other organizations working alongside WHO (World Health Organization). Since its inception, the program has been implemented smoothly and reported cases of infection have dramatically declined from 3.5 million in 1986 to 22 in 2015. Guinea worm disease eradication is now in its final stages.

References
WHO- Neglected Tropical Diseases, accessed March 19, 2014,
http://www.who.int/neglected_diseases/mediacentre/factsheet/en/
CDC- Neglected Tropical Diseases, accessed March 19, 2014,
http://www.cdc.gov/globalhealth/ntd/diseases/