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Dracunculiasis (guinea-worm disease)

13 September 2024

Key facts

• Dracunculiasis is a crippling parasitic disease on the verge of eradication, with 14 human cases reported in 2023 and 13 in 2022.
• From the time infection occurs, it takes between 10–14 months for the transmission cycle to complete. About this time, a mature female worm emerges from the body.
• The parasite is transmitted mostly when people drink stagnant water contaminated with parasite-infected water fleas.
• Dracunculiasis was endemic in 20 countries (1)in the mid-1980s. 

Overview

Dracunculiasis, also called Guinea worm disease, is a disease caused by the parasite Dracunculus medinensis. It is rarely fatal, but infected people become non-functional for weeks and months. It affects people in rural, deprived, and isolated communities who depend mainly on open stagnant surface water sources such as ponds for drinking water.

Scope of the problem

During the mid-1980s an estimated 3.5 million cases of dracunculiasis occurred in 20 countries worldwide, 17 countries of which were in Africa and the 3 others in Asia. The number of reported cases fell to fewer than 10 000 cases for the first time in 2007, dropping further to 542 cases in 2012 and 126 in 2014. Since 2015, human cases have stayed at double digits (from 22 in 2015 to 14 human cases in 2023). In 2023, human cases were reported from only 11 villages in five countries: Chad (9 cases), Mali (1 case), South Sudan (2 cases), and one case each from Cameroon and Central African Republic, which are both certified countries – in both instances, cases were imported from Chad.

Currently, 5 countries (Angola, Chad, Ethiopia, Mali and South Sudan) are considered as endemic, while Sudan is in the pre-certification stage.  

Transmission, life cycle and incubation period

About a year after 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 part of the body 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 (which measures 60–100 cm long) migrates under the skin tissues until it reaches its exit point, usually at the lower limbs, forming a blister or swelling from which it eventually emerges. The worm takes 10–14 months to emerge after infection.

Prevention

There is no vaccine to prevent the disease, nor is there any medication to treat patients. Prevention is possible, however, and successful implementation of preventive strategies have driven the disease to the verge of eradication. Prevention strategies include:

• heightening surveillance to detect every human case and infected animal within 24 hours of worm emergence;
• preventing complications (wound infection and septicemia) by treating each wound where a worm emerged, and regularly cleaning and bandaging the affected areas of skin until the worm is completely expelled from the body;
• preventing contamination of drinking water by ensuring that infected people and infected animals (dogs and cats) with emerging worms do not wade into water;
• ensuring wider access to improved drinking-water supplies;
• filtering water from open and stagnant water bodies before drinking;
• implementing vector control by using the larvicide temephos; and
• promoting health education and behavioural change.

The road to eradication

Elimination and then eradication of dracunculiasis has been endorsed by the WHO’s decision-making body, the World Health Assembly, through various resolutions: WHA39.21 (1986), WHA42.29 (1989), WHA44.5 (1991), WHA57.9 (2004), WHA64.16 (2011). In May 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, the World Health Assembly adopted resolution WHA34.25, 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 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 at the forefront of eradication activities. To give it a final push, in 2011 the World Health Assembly, through resolution WHA64.16, called on all Member States where dracunculiasis is endemic to expedite the interruption of transmission and enforce nationwide surveillance to ensure eradication of dracunculiasis.

Country certification

To be declared free of dracunculiasis, a country is required to have reported zero human cases and animal infections for at least 3 consecutive years, during which active surveillance has been maintained.

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 or infected animals and subsequent actions taken.

Indicators such as access to improved drinking-water sources in infected areas are examined and assessments are conducted in villages to confirm the absence of transmission. Risks of reintroduction of the disease are also assessed. Finally, a report is submitted to the International Commission for the Certification of Dracunculiasis Eradication (ICCDE) for review.

Since 1995, the ICCDE has met 16 times and on its recommendation, WHO has certified 199 countries, territories, and areas (belonging to 187 Member States) as free of dracunculiasis. The Democratic Republic of the Congo, a formerly endemic country, was the last to attain this status in December 2022.

The latest update to the criteria for the certification of dracunculiasis eradication was published by WHO in 2023.

Ongoing surveillance

WHO recommends active surveillance in a country and/or area that has recently interrupted Guinea worm disease transmission to be maintained for a minimum of 3 consecutive years. Ongoing surveillance is essential to ensure that no human cases and infected animals have been missed and to prevent reoccurrence of the disease.

As the incubation period of the worm takes 10–14 months, a single missed emerged worm could delay eradication by a year or more. Evidence of re-emergence was brought to light in Ethiopia (2008) after the national eradication programme 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 classified as being in the pre-certification stage for at least 3 years since the last indigenous case, during which intense surveillance activities must be continued. Even after certification, surveillance should be maintained until global eradication is declared.

Challenges

Finding and containing the last remaining cases and infected animals are the most difficult and expensive stages of the eradication process, as these usually occur in remote, often inaccessible, rural areas.

Insecurity, with the resulting lack of access to disease-endemic areas, is a major constraint.

Also, infections in humans and/or in animals (mostly dogs) are increasingly being reported in certified countries that share borders with countries where transmission still occurs. This highlights the risk of reintroduction of transmission and the need for sustained and adequate post-certification surveillance, including cross-border surveillance, until global eradication is declared.  

Dracunculus medinensis infection in dogs continues to pose a challenge to the global eradication campaign particularly in Chad, Ethiopia and Mali. The phenomenon was noted in Chad in 2012, and since then several dogs with emerging worms, genetically identical to those emerging in humans, continue to be detected in the same at-risk area. In 2023, Chad reported 406 infected dogs and 88 infected cats; Ethiopia reported 1 infected dog; Mali reported infections in 41 dogs, 5 cats and 1 donkey.

Transmission in animals can be interrupted through enhanced surveillance aimed at detecting all infected animals and containing them (tethering of infected animals and pro-active tethering), provision of health education for community members and animal owners, and implementation of vigorous and comprehensive vector control interventions. 

WHO response

In response to dracunculiasis, and in collaboration with Member States and key partners, WHO advocates for eradication, provides technical guidance, coordinates eradication activities, enforces surveillance in dracunculiasis-free areas and monitors and reports on progress achieved.

WHO is the only organization mandated to certify countries as free of the disease transmission following recommendations made by the ICCDE. 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 country should be certified as free of dracunculiasis transmission.

 

 

Notes

1. Until South Sudan gained its independence on 9 July 2011, it was part of Sudan. Guinea-worm disease cases for South Sudan were reported under Sudan; thus, between the 1980s and 2011, 20 countries were endemic for the disease.