Progress Toward Global Eradication of Dracunculiasis, January 2020–June 2021

Dracunculiasis (Guinea worm disease), caused by the parasite Dracunculus medinensis, is traditionally acquired by drinking water containing copepods (water fleas) infected with D. medinensis larvae, but in recent years also appears increasingly to be transmitted by eating fish or other aquatic animals. The worm typically emerges through the skin on a lower limb of the host 1 year after infection, causing pain and disability (1). There is no vaccine or medicine to prevent or medicine to treat dracunculiasis; eradication relies on case containment* to prevent water contamination and other interventions to prevent infection: health education, water filtration, treatment of unsafe water with temephos (an organophosphate larvicide), and provision of safe drinking water (1,2). The eradication campaign began in 1980 at CDC (1). In 1986, with an estimated 3.5 million cases^† occurring annually in 20 African and Asian countries^§ (3), the World Health Assembly called for dracunculiasis elimination (4). The Guinea Worm Eradication Program (GWEP), led by The Carter Center and supported by the World Health Organization (WHO), UNICEF, CDC, and other partners, began assisting ministries of health in countries with endemic disease. With 27 cases in humans reported in 2020, five during January–June 2021, and only six countries currently affected by dracunculiasis (Angola, Chad, Ethiopia, Mali, South Sudan, and importations into Cameroon), achievement of eradication appears to be close. However, dracunculiasis eradication is challenged by civil unrest, insecurity, and epidemiologic and zoologic concerns. Guinea worm infections in dogs were first reported in Chad in 2012. Animal infections have now overtaken human cases, with 1,601 reported animal infections in 2020 and 443 during January–June 2021. Currently, all national GWEPs remain fully operational, with precautions taken to ensure safety of program staff and community members in response to the COVID-19 pandemic. Because of COVID-19, The Carter Center convened the 2020 and 2021 annual GWEP Program Managers meetings virtually, and WHO’s International Commission for the Certification of Dracunculiasis Eradication met virtually in October 2020. Since 1986, WHO has certified 199 countries, areas, and territories dracunculiasis-free. Six countries are still affected: five with endemic disease and importations into Cameroon. Seven countries (five with endemic dracunculiasis, Democratic Republic of the Congo, and Sudan) still lack certification (4). The existence of infected dogs, especially in Chad, and impeded access because of civil unrest and insecurity in Mali and South Sudan are now the greatest challenges to interrupting transmission. This report describes progress during January 2020–June 2021 and updates previous reports (2,4,5).

In 2020, Angola, Cameroon, Chad, Ethiopia, Mali, and South Sudan reported 27 cases in humans; Cameroon, Chad, Ethiopia, and Mali reported 1,601 infected animals (mostly domestic dogs), compared with 54 cases in humans and 2,000 infections in animals in 2019 (Table 1). During January–June 2021, five cases were reported in Chad (four) and Ethiopia (one), and 443 infected animals were reported in Chad (441) and Mali (two), compared with 19 cases and 1,115 animal infections during January–June 2020. This difference equates to a 74% reduction in human cases and a 60% reduction in animal infections during this 6-month period in 2021 compared with 2020. During January–June 2021, CDC received 13 specimens from humans for morphologic or molecular identification, including five that were laboratory-confirmed D. medinensis^¶ (Table 2), compared with 44 received and 21 (41%) confirmed during January–June 2020. During the first 6 months of 2021, CDC received 36 animal specimens, six (17%) of which were confirmed, compared with 19 received and five confirmed during January–June 2020. D. medinensis worms from animals are genetically indistinguishable from those removed from humans (6). This activity was reviewed by CDC and was conducted consistent with applicable federal law and CDC policy.**

In affected countries, the national GWEP receives monthly case reports from supervised volunteers in villages under active surveillance^†† (Table 3). Villages where endemic transmission has ended (i.e., zero cases or animal infections reported for ≥12 consecutive months) are kept under active surveillance for 2 additional years. WHO certifies a country as dracunculiasis-free after adequate nationwide surveillance for ≥3 consecutive years with no indigenous cases or animal infections.^§§

Corresponding author: Sharon L. Roy, str2@cdc.gov, 404-718-4698.

¹The Carter Center, Atlanta, Georgia; ²World Health Organization Collaborating Center for Dracunculiasis Eradication, Division of Parasitic Diseases and Malaria, Center for Global Health, CDC.

References

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* Cameroon reported one human case, five infected dogs, and one infected cat in 2020 in villages <3 miles (<5 km) from the Chad-Cameroon border that were likely infected in Chad because the affected villages included families living on both sides of the border.
^† Civil unrest and insecurity since a coup d’état in April 2012 continued to constrain Guinea Worm Eradication Program operations (e.g., supervision, surveillance, and interventions) in Gao, Kidal, Mopti, Segou, and Timbuktu regions.
^§ In Chad, primarily dogs, some cats; in Ethiopia, dogs, cats, and baboons; in Mali, dogs and one cat (2019); in Angola, one dog; in Cameroon, dogs and one cat.

* Specimens did not come from this country.
† The category “Free-living nematodes” primarily included adult Mermithidae and other nematodes identified as belonging to nonparasitic taxa. “Other parasitic nematodes” included non-Onchocerca nematodes identified as belonging to parasitic taxa.
^§ No specimens received this diagnosis.
^¶ “Other parasitic nematodes” submitted in association with cases in humans in 2020 included Eustrongyloides sp. (one) and filarial nematodes not fully identified (four).
** “Other worms” submitted in association with one case in a human in 2020 included an annelid (one); a horsehair (Gordian) worm (one); a specimen vial that contained two Acanthocephala not identified further and one Toxocara; and one nematode not able to be identified further.
^†† The “Other” specimen submitted in association with one case in a human in 2020 included a small (approximately 15 cm) blind snake (infraorder Scolecophidia).
^§§ Two worms were submitted from one dog.
^¶¶ No specimen came from that country or that species.
*** “Other parasitic nematodes” submitted in association with animal cases in 2020 included Dirofilaria sp. (two), Filaria sp. (11), Physaloptera sp. (two), Protospirura sp. (one), Skrjabinodera sp. (three), Spirocerca sp. (one), spirurid nematodes (two), and Toxocara cati (two). Submissions during January–June 2021 included Eustrongyloides sp. (one), Dirofilaria sp. (two), Skrjabinodera sp. (one), filarial nematodes not identified to genus (16), a worm belonging to the Gnathostoma taxon (one), and a spirurid nematode not identified to genus (one).
^††† “Other worms” submitted in association with one case in an animal in 2020 included an Acanthocephala not identified further (one), cestodes not identified further (two), nematode not identified further (one), and a horsehair worm (one).
^§§§ The “Other” specimens submitted in association with animal cases in 2020 were small snakes (two) and a fly larva (one).

* Participants at the annual Chad Guinea Worm Eradication Program review meeting in November 2014 adopted “1+ case village” as a new description for villages in Chad affected by cases in humans of Guinea worm disease or dogs infected with Guinea worms and defined it as “a village with one or more indigenous and/or imported cases of Guinea worm infections in humans, dogs, and/or cats in the current calendar year and/or previous year.”
^† Civil unrest and insecurity since a coup d’état in April 2012 continued to constrain Guinea Worm Eradication Program operations (e.g., supervision, surveillance, and interventions) in Gao, Kidal, Mopti, Segou, and Timbuktu regions.
^§ Twelve cases were reported from Chad in 2020. One case was reported from Cameroon in 2020 in a village along the Chad-Cameroon border which is believed to have been acquired in Chad because the affected villages included families living on both sides of the Cameroon-Chad border.
^¶ Imported from another country.
** Transmission from a patient with dracunculiasis is contained only if all of the following conditions are met for each emerged worm: 1) the infected patient is identified ≤24 hours after worm emergence; 2) the patient has not entered any water source since the worm emerged; 3) a village volunteer or other health care provider has managed the patient properly by cleaning and bandaging the lesion until the worm has been fully removed manually and by providing health education to discourage the patient from contaminating any water source (if two or more emerging worms are present, transmission is not contained until the last worm is removed); 4) the containment process, including verification of dracunculiasis, is validated by a Guinea Worm Eradication Program supervisor within 7 days of emergence of the worm; and 5) temephos is used to treat potentially contaminated surface water if any uncertainty about contamination of these sources of drinking water exists or if such a source of drinking water is known to have been contaminated.
^†† Chad reported 1,571 animal cases in 2020. Six cases in animals were reported from Cameroon in 2020, all in villages along the Chad-Cameroon border; these are believed to have been acquired in Chad.
^§§ Imported from another in-country disease-endemic village.
^¶¶ The denominator is number of villages with endemic human or animal dracunculiasis reported during 2019–2020.
*** By the end of 2020, Angola established active surveillance in 54 villages, but a system for regular data reports from each village was not yet established.
^††† The case in a human in Mali was imported from another location within Mali. The village of detection is not considered endemic because the case was not indigenous to the village of detection. Therefore, interventions such as monthly reporting, filter distribution, temephos use, and safe water source counting were not implemented in the village of detection and were not applicable.