Guinea Worm Disease Near Eradication: Progress, January 2023–June 2024

Dracunculiasis, or Guinea worm disease, is caused by the parasite Dracunculus medinensis. People catch it by drinking water containing tiny crustaceans called copepods (water fleas) infected with the parasite's larvae, and recent evidence suggests it may also spread through undercooked fish or other aquatic animals. About a year after infection the worm emerges through the skin, usually on a leg, causing pain and disability. There is no vaccine or medicine. Eradication depends on:

• case containment — finding patients within 24 hours of a worm emerging, keeping them out of water sources, treating the wound until the worm is fully removed, and treating possibly contaminated water;
• tethering infected dogs;
• health education, water filtration and treating unsafe water with the larvicide temephos;
• safe drinking water, cooking aquatic animals thoroughly and burying fish entrails.

A long campaign

CDC began working to eradicate the disease in 1980 and in 1984 became the World Health Organization's technical monitor for the effort. In 1986, with an estimated 3.5 million cases a year in 20 countries in Africa and Asia, the World Health Assembly called for its elimination. The Guinea Worm Eradication Program (GWEP), led by The Carter Center with CDC, UNICEF, WHO and the affected countries, has helped health ministries since. WHO has certified 200 countries, areas and territories free of the disease; it certifies a country after at least 3 straight years of adequate nationwide surveillance with no local human or animal infection.

As of June 2024 the disease remained endemic in five countries — Angola, Chad, Ethiopia, Mali and South Sudan — and Sudan had not yet completed certification. Since 2012, infections in animals, mostly domestic dogs and especially in Chad, have complicated eradication; worms from these animals are genetically confirmed as D. medinensis.

The numbers

The 14 human cases of 2023 — in Cameroon, the Central African Republic, Chad, Mali and South Sudan — were the second-lowest yearly total ever, far below the 5,911 of 2007, and for the second year running no cases occurred for 6 months (January–April and November–December). Animal infections rose 30% in 2023 but were still far below the 1,944 dog infections of 2019, and fell 45% in the first half of 2024. Chad accounted for about half of all remaining infections, nearly 90% of them in dogs. Investigators identified where people were probably infected in only 4 of the 14 cases in 2023, against 11 of 13 in 2022.

In the first half of 2024, CDC confirmed one of seven human specimens and 434 (90%) of 482 animal specimens as D. medinensis.

Country by country

• Angola: 158 communities under active surveillance in 2023; 85 infected dogs in 2023 and 36 in the first half of 2024, all in the same province as before. Genetic analysis has not linked its worms to other countries'. It offers a reward worth US$450 for reporting an infection, tethers at-risk dogs and uses temephos.
• Cameroon: 255 infected animals (248 dogs and seven cats) and one human case in 2023; 115 dogs and two cats in the first half of 2024, all in villages within 3 miles (5 km) of the Chad border. The animals were probably infected in Chad, where many families also live and take their dogs.
• Chad: 10 human cases in 2023, three in one household (plus one detected in the Central African Republic), and one in the first half of 2024. Animal infections declined for the fourth and fifth consecutive years, to 144 in the first half of 2024. Surveillance covered 2,768 at-risk villages; reports of possible cases ("rumors") rose 51%, from 110,784 to 166,996, between the first halves of 2023 and 2024. Rewards are worth US$100 for a confirmed human case and US$20 for an animal; 70% of residents surveyed in 2023 and 89% in 2024 knew of them. Some 43% and 34% of at-risk households buried fish entrails; 81% and 74% of eligible dogs were tethered; temephos reached 87% of 279 affected villages by December 2023 and 98% of 96 by June 2024; and 79% of affected villages had at least one copepod-free water source. The health minister visited an endemic area in June 2023, and eight provincial governors pledged action in 2024.
• Ethiopia: one infected dog and no human cases in 2023, none in the first half of 2024. Baboons are trapped and examined; one dead baboon had a non-emerged worm in April 2024, which does not count as a case. Surveillance covers 198 villages and 223 other areas across about 50 by 25 miles in Gog and part of Abobo districts. Since 2018 villagers have kept about 1,900 dogs and cats tethered, and nearly all water sources used by people or infected animals get monthly temephos, with remote sensing used since 2022 to find new ones. Rewards: US$360 for a human case, US$40 for reporting and tethering an animal.
• Mali: one human case in 2023 and none in the first half of 2024; 47 infected animals in 2023 (44 in Segou Region, three in Mopti Region, in areas hard to reach because of civil unrest) and none in the first half of 2024. Some 1,965 villages were under surveillance, with rewards of US$340 and US$20; dogs, and since 2023 puppies, are tethered in the June–September peak season.
• South Sudan: two human cases in 2023 (down from five in 2022) and two in the first half of 2024; its first infected wildcat, a genet, in November 2023. Mobile cattle herders and insecurity complicate the work; 2,584 villages were under surveillance, and the reward for a human case doubled from US$375 to US$750.

The challenges

Animals. In Chad, dogs are thought to be infected mainly by eating undercooked aquatic animals, including fish and other hosts that carry larvae; heavy contamination by many infected dogs then spreads the parasite to a few people, cats and more dogs. Stopping transmission among dogs is now the program's main focus. Proactive tethering of dogs in at-risk villages, pioneered by Ethiopia in 2018, has proven effective and was adopted by Chad in 2020, Mali and Cameroon in 2022 and Angola in 2023. Baboon infections in Ethiopia appear to be falling with intensive temephos treatment.

Security. Mali's program uses health services as a route to peacebuilding through a Peace through Health Initiative, begun in one district in 2020 and expanded to four in 2022, but it needs peace to work in all six endemic districts during its 6-month transmission season. With adequate security and no sustained animal transmission, Ethiopia and South Sudan appear close to elimination. Human cases in Angola, in Cameroon near Chad, and in the Central African Republic show the risk of spread across borders.

Why it matters

Eradication would likely make dracunculiasis the second human disease ever eradicated, after smallpox — and the first without a vaccine or cure. Millions of people are no longer at risk, with gains in health, farm productivity and schooling, and the program has trained many health officers and thousands of village volunteers. Surveillance still has gaps — deliberate underreporting, missed cases and areas made inaccessible by insecurity — and the extent of infection in wildlife is hard to measure.

Sources

Based on Hopkins DR, Weiss AJ, Yerian S, et al., "Progress Toward Global Dracunculiasis (Guinea Worm Disease) Eradication, January 2023–June 2024," MMWR Vol. 73, No. 44, CDC; a work of the United States government in the public domain. The report gives Chad's animal infections as 601 in 2022, 496 in 2023 (18% fewer) and 219 in January–June 2023 in one section, and as 602, 497 (17% fewer) and 221 in another; those figures are not given here.