Guinea Worm Disease Near Eradication: Progress, January 2019–June 2020

Dracunculiasis, or Guinea worm disease, is caused by the parasite Dracunculus medinensis. People catch it by drinking water containing tiny copepods (water fleas) infected with the worm’s larvae. About a year later the worm emerges through the skin, usually on a leg, causing pain and disability. There is no vaccine and no medicine for it. Eradication depends on containing each case so no one contaminates water, plus health education, filtering water, treating unsafe water with the larvicide temephos, and providing safe drinking water.

From millions to dozens

The global eradication campaign began at CDC in 1980. In 1986, when an estimated 3.5 million cases a year occurred in 20 countries in Africa and Asia, the World Health Assembly called for the disease to be eliminated. The Guinea Worm Eradication Program, led by The Carter Center with the World Health Organization (WHO), UNICEF, CDC and others, has helped health ministries ever since. WHO has certified 199 countries, areas and territories free of human Guinea worm disease; seven countries still lack certification.

In 2019 human cases came from Angola, Cameroon, Chad and South Sudan. In the first half of 2020 they came from Chad (9), Ethiopia (7), Mali (1), Cameroon (1, probably infected in Chad) and Angola (1). South Sudan reported none. Worms from animals are genetically and physically indistinguishable from those in people.

A village with no cases for 12 straight months stays under active surveillance for two more years, and WHO certifies a country only after at least three consecutive years of adequate nationwide surveillance with no indigenous human or animal infections.

Country by country

• Chad accounted for 3,096 (99%) of the world’s 3,136 infections from January 2019 to June 2020 — 95% of them in dogs. It reported 48 human cases in 2019, 22 of them tied to one village in Salamat Region, its first waterborne outbreak in people since 2010, and 1,935 infected dogs and 47 cats, nearly double 2018. The working theory is that people and animals are infected by eating undercooked fish or other aquatic hosts. Chad asks villagers to cook fish well and bury fish entrails, tethers infected dogs until their worms emerge (77% in 2019, 87% in early 2020), and pays rewards for reports — US$100 for a person, US$20 for an animal — which 86% of residents surveyed knew about in 2020. In March 2020 it began tethering dogs proactively during the four peak months in the 118 villages with five or more infections in 2019.
• Ethiopia had no human cases in 2018–2019 but seven in early 2020, among villagers who shared a contaminated water source near Duli village in Gambella Region. Infected dogs and baboons in Gog district are the subject of a Carter Center–supported study, and about 1,100 dogs and cats are kept tethered.
• Mali reported no human case for four years until one in early 2020. Insecurity has kept the program out of parts of Mopti Region since 2012, and infected dogs bred there have been sold in neighboring Segou.
• South Sudan reported 4 human cases in 2019, down from 10 in 2018, and none in early 2020; the mobility of cattle herders and sporadic insecurity are its main challenges.
• Angola had never reported a case before April 2018. It has since found three human cases and one infected dog, all in Cunene Province, suggesting a limited problem that still needs surveillance.

What stands in the way

The pattern of many infected dogs and few people is peculiar to Chad. Research with the University of Georgia has shown in the laboratory that fish can carry Dracunculus and that frogs can serve as hosts in which the larvae do not develop, and larvae have been found in wild frogs in Chad. If that is how the parasite spreads there, surveillance, tethering, temephos and burying fish entrails should cut transmission. Cases exported to Cameroon show the need for surveillance in neighboring countries, and outbreaks from shared water in Chad in 2019 and Ethiopia in 2020 show the need for safe drinking water. With security, South Sudan appeared close to reaching zero cases; in Mali, insecurity remained the main obstacle.

Despite COVID-19, all national programs kept operating, with precautions for staff and communities.

Sources

Based on Hopkins DR, Weiss AJ, Roy SL, Yerian S, Sapp SGH, "Progress Toward Global Eradication of Dracunculiasis, January 2019–June 2020," Morbidity and Mortality Weekly Report, Centers for Disease Control and Prevention; written with The Carter Center and rewritten in hubnx’s own words. The report’s opening paragraph dates the 19 human cases to January 2019–June 2020; its summary and country figures place them in January–June 2020, as here.