Dracunculiasis (guinea-worm disease)
Fact sheet N°359
October 2011
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Key facts
• Dracunculiasis is a crippling parasitic disease on verge of eradication, with fewer than 1 800 cases reported in 2010.
• It is transmitted exclusively when people who have little or no access to safe-drinking water supply swallow water contaminated with parasite-infected fleas.
• Of the 20 countries that were endemic in the mid 1980s, only 4 (all on the African continent) are still reporting cases.
• Most cases (97%) occur in newly independent South Sudan.
• From the time infection occurs, it takes between 10-14 months for the cycle to complete until a mature worm emerges from the body.
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Dracunculiasis (more commonly known as guinea-worm disease) is a crippling parasitic disease caused by Dracunculus medinensis, a long thread-like worm. It is transmitted exclusively when people drink water contaminated with parasite-infected water fleas.
Dracunculiasis is rarely fatal but infected people become non-functional for months. It affects people in rural, deprived and isolated communities who depend mainly on open water sources such as ponds.
Scope of the problem
During the mid 1980s there were an estimated 3.5 million cases in 20 countries worldwide, 16 of which were in Africa. The number of reported cases declined throughout the 1990s to reach fewer than 10 000 cases in 2007. This number dropped further to 4 619 in 2008, then to 3 190 in 2009 and to 1 797 in 2010.
As of 2011, the annual incidence of the disease has decreased by more than 99% compared to the mid 1980s. Currently, the only reported cases have been in Chad, Ethiopia, Mali and South Sudan.
Transmission, life-cycle and incubation period
About one year after the infection, a painful blister forms - 90% of the time on the lower leg – and one or more worms emerge accompanied by a burning sensation. To soothe the burning pain, patients often immerse the infected area in water. The worm(s) then releases thousands of larvae (baby worms) into the water.These larvae reach the infective stage after being ingested by tiny crustaceans or copepods, also called water fleas.
People swallow the infected water fleas when drinking contaminated water. The water fleas are killed in the stomach but the infective larvae are liberated. They then penetrate the wall of the intestine and migrate through the body. The fertilized female worm(s) (which measures from 60–100 cm long) migrates under the skin tissues until it reaches the lower limbs, forming a blister or swelling from which it eventually emerges. The migration and emergence (incubation period) of the worm(s) take between 10 to 14 months after infection.
Prevention
There is no vaccine to prevent nor is there any medication to treat the disease. However prevention is possible and it is through preventive strategies that the disease is on the verge of eradication. Some of these strategies are:
• heightening surveillance to detect every case within 24 hours of the worm emergence;
• preventing transmission from each worm by treatment, cleaning and bandaging regularly the affected skin-area until the worm is completely expelled from the body;
• preventing drinking water contamination by advising the patient to avoid wading into water;
• ensuring wider access to safe drinking-water supplies to prevent infection;
• filtering water from open water bodies before drinking;
• implementing vector control by using the larvicide temephos;
• promoting health education and behavior change.
Road to eradication
In April 1981, the Interagency Steering Committee for Cooperative Action for the International Drinking Water Supply and Sanitation Decade (1981–1990) proposed the elimination of dracunculiasis as an indicator of success of the Decade. In the same year, WHO's decision-making body, the World Health Assembly (WHA), adopted a resolution (WHA 34.25) recognizing that the International Drinking Water Supply and Sanitation Decade presented an opportunity to eliminate dracunculiasis. This led to WHO and the United States Centers for Disease Control and Prevention (CDC) formulating the strategy and technical guidelines for an eradication campaign.
In 1986, the Carter Center joined the battle against the disease and in partnership with WHO and UNICEF has since been in the forefront of eradication activities. To give it a final push, in 2011 the WHA called on all Member States where dracunculiasis is endemic to expedite the interruption of transmission and enforce nation-wide surveillance to ensure eradication of dracunculiasis.
Country certification
To be declared free of dracunculiasis, a country needs to have reported zero transmission and afterwards maintained active surveillance for at least three years.
After this period, an international certification team visits the country to assess the adequacy of the surveillance system and to review records of investigations regarding rumoured cases and subsequent actions taken.
Indicators such as water supplies in infected areas are examined and assessments are carried out in villages to confirm the absence of transmission. Risks of reintroduction of the disease is also assessed. Finally a report is submitted to the ICCDE for review.
Since 1995 the ICCDE has met seven times and on its recommendation WHO has certified 187 countries and territories as free of dracunculiasis.
On-going surveillance
Active surveillance in a country that has recently interrupted guinea-worm disease transmission should be maintained for a minimum period of three years. This is WHO's criteria to make sure there has been no missed cases and to ensure no reoccurrence of the disease.
As the incubation period of the worm takes between 10-14 months, a single missed case will delay eradication efforts by one year or more. Evidence of re-emergence was brought to light in Ethiopia (2008) even though the national eradication programme had claimed interruption of transmission and more recently in Chad (2010) where transmission re-occurred after the country reported zero cases for almost 10 years.
A country reporting zero cases over a period of 14 consecutive months is believed to have interrupted transmission. It is then considered for pre-certification for at least three years during which intense surveillance activities need to continue. Even after certification, surveillance should be maintained until global eradication is declared.
Challenges
Finding and containing the last remaining cases may be the most difficult stage of the eradication process as cases usually occur in remote often inaccessible rural areas.
Insecurity, with the resulting lack of access to disease-endemic areas, is a major constraint, especially in countries where cases are still occurring, namely Chad, Ethiopia, Mali and South Sudan.
There is also a risk of complacency when case numbers decrease, resulting in a decrease in funding and interest. Funding and interest can also diminish during the less visibly rewarding surveillance phase.
WHO response
WHO provides technical guidance, coordinates eradication activities, enforces surveillance in dracunculiasis-free areas and advocates for eradication.
WHO is the only organization mandated to certify countries as free of the disease following recommendations made by the International Commission for the Certification of Dracunculiasis Eradication (ICCDE). The ICCDE comprises 12 public health experts from the six WHO Regions. The Commission meets as and when necessary to evaluate the status of transmission in countries applying for certification of dracunculiasis eradication and to recommend whether a particular country should be certified as free of transmission.