Progress Toward Global Eradication of Dracunculiasis, January 2014–June 2015

Donald R. Hopkins, MD1; Ernesto Ruiz-Tiben, PhD1; Mark L. Eberhard, PhD2; Sharon L. Roy, MD3

Dracunculiasis (Guinea worm disease) is caused by Dracunculus medinensis, a parasitic worm. Approximately 1 year after a person acquires infection from contaminated drinking water, the worm emerges through the skin, usually on the lower limb. Pain and secondary bacterial infection can cause temporary or permanent disability that disrupts work and schooling. The campaign to eradicate dracunculiasis worldwide began in 1980 at CDC. In 1986, the World Health Assembly called for dracunculiasis elimination (1), and the global Guinea Worm Eradication Program, led by the Carter Center and supported by the World Health Organization (WHO), United Nations Children's Fund (UNICEF), CDC, and other partners, began assisting ministries of health in countries where dracunculiasis was endemic. In 1986, an estimated 3.5 million cases occurred each year in 20 countries in Africa and Asia (1,2). Since then, although the goal of eradicating dracunculiasis has not been achieved, considerable progress has been made. Compared with the 1986 estimate, the annual number of reported cases in 2015 has been reduced by 99% and cases are confined to four endemic countries. This report updates published (3–5) and unpublished surveillance data reported by ministries of health and describes progress toward dracunculiasis eradication from January 2014 through June 2015. During 2014, a total of 126 cases were reported from four countries (Chad [13 cases], Ethiopia [three], Mali [40], and South Sudan [70]), compared with 148 cases reported in 2013, from the same four countries. The overall 15% reduction in cases during 2013–2014 was less than that experienced in recent years, but the rate of decline increased again to 70% in the first 6 months of 2015 compared with the same period during 2014. Continued active surveillance with aggressive detection and appropriate management of cases are essential program components; however, epidemiologic challenges and civil unrest and insecurity pose potential barriers to eradication.

Because the life cycle of D. medinensis is complex, its transmission can be interrupted using several strategies (4). Dracunculiasis can be prevented with four main interventions: 1) educating residents in communities where the disease is endemic, particularly persons from whom worms are emerging, to avoid immersing affected body parts in sources of drinking water; 2) filtering potentially contaminated drinking water through a cloth filter or pipe filter; 3) treating potentially contaminated surface water with the insecticide temephos (Abate) to kill the copepods (small crustaceans that host D. medinensis larvae); and 4) providing safe drinking water from bore-hole or protected hand-dug wells (6). Containment of transmission* is achieved through four complementary measures: 1) voluntary isolation of each patient to prevent contamination of drinking water sources, 2) provision of first aid to prevent secondary infections, 3) manual extraction of the worm, and 4) application of occlusive bandages. No vaccine or medicine to prevent or treat Guinea worm disease currently exists.

D. medinensis has approximately a 1-year incubation period (range = 10–14 months) following infection (6). A case of dracunculiasis is defined as an infection occurring in a person exhibiting a skin lesion or lesions with emergence of one or more Guinea worms. Each infected person is counted as a case only once during a calendar year. Countries enter the WHO precertification stage of eradication after 1 full year with no reported indigenous† cases. An imported case is an infection resulting from ingestion of contaminated water from a source identified through patient interviews and epidemiologic investigation in a place other than in the community where the patient is detected and reported (i.e., another country or village within the same country). Since 2012, no known cases imported from one country to another have been reported.

In each affected country, a national dracunculiasis eradication program receives monthly reports regarding cases from each village under active surveillance. Reporting rates are calculated as the proportion of all villages under active surveillance reporting monthly. Active surveillance is conducted in all villages with endemic dracunculiasis or at high risk for importation, with daily searches of households for persons with signs or symptoms of dracunculiasis, to ensure case detection within 24 hours of worm emergence and prompt patient management to prevent contamination of water sources. Villages where endemic transmission of dracunculiasis is interrupted (i.e., zero cases reported for ≥12 consecutive months) are kept under active surveillance for 3 consecutive years. WHO certifies a country free from dracunculiasis after that country maintains adequate nationwide surveillance for ≥3 consecutive years and demonstrates that no cases of indigenous dracunculiasis occurred during that period. As of January 2015, WHO had certified 198 countries, areas, and territories as free from dracunculiasis (3). Eight countries remain to be certified: four where dracunculiasis is currently endemic (Chad, Ethiopia, Mali, and South Sudan), two in the precertification stage (Kenya and Sudan), and two never known to have had endemic dracunculiasis since the global eradication program began in 1980 (Angola and the Democratic Republic of the Congo).

During January 2014–June 2015, CDC evaluated 385 specimens that emerged from humans. Among these, six were collected in four formerly endemic countries (Ghana, Kenya, Niger, and Sudan) and the remaining 379 were collected in the four countries where dracunculiasis remains endemic. In total, 164 specimens (43%) were determined to be D. medinensis, all of which came from the four endemic countries. Because some patients have multiple Guinea worms emerge, more laboratory-confirmed specimens than cases might be reported.

Country Reports

Chad. Following a decade with no reported cases, Chad reported 10 cases in 2010, and after indigenous cases were confirmed over 3 consecutive years, dracunculiasis was declared to be endemic in 2012 (7,8). In 2014, Chad reported 13 cases (eight contained) in 11 villages, compared with 14 cases in 2013. During the first half of 2015, six cases (zero contained) were reported in six villages, the same as the number of cases reported in the same period of 2014, four of which were contained. Only one of the 11 villages that reported a case in 2014 and none of the six villages that reported a case during January–June 2015 had previously reported a case.

Guinea worm infections in dogs in Chad were first detected in 2012 and since then, more dogs than humans have been identified with emerging Guinea worms in this country. This has not occurred in any other country during the eradication campaign. Worm specimens obtained from dogs were determined to be genetically indistinguishable from D. medinensis worms removed from humans in Chad (7). Most infections during the current outbreak have occurred in communities along the Chari River. The Carter Center has assisted the Ministry of Health in implementing active village-based surveillance for the disease in more than 700 villages in the at-risk zone. The working hypothesis, based on biologic, environmental, and epidemiologic investigations by CDC and the Carter Center, is that the cases in humans and infected dogs are associated with the domestic and commercial fishing industry along the Chari River and involve fish or other aquatic hosts that serve as paratenic hosts (intermediate hosts in which no development of the parasite occurs). New human cases are thought to occur when inadequately cooked paratenic hosts are consumed by humans and when such hosts, including fish and fish entrails, are consumed raw by dogs (7). Overall, 113 infected dogs were reported in 2014; during January–June 2015, 302 infected dogs were reported, a 325% increase over the 71 reported during the same period in 2014.

Beginning in October 2013, Chad's Guinea Worm Eradication Program urged villagers to cook their fish well, bury fish entrails, and prevent dogs from eating fish entrails. By May 2015, according to monthly sample surveys, this intervention was being implemented in more than half of the at-risk population in surveyed communities. In February 2014, efforts began to persuade villagers to tether infected dogs until the worms emerged to prevent contamination of water and infection of copepods.

Chad has offered a cash reward equivalent to about US$100 for reporting a case of dracunculiasis in humans since before 2010. Since February 2015, a cash reward equivalent to about US$20 for reporting and tethering infected dogs has been offered. The Minister of Health visited seven endemic villages in March 2015 to help mobilize local authorities and villagers and publicize the cash rewards. Whereas 40% of infected dogs were tethered in 2014, 70% were tethered during January–June 2015. As of April 2015, among 127 villages that had an infected human or dog during 2014–2015, 81 (64%) had at least one source of safe drinking water. Temephos usage is limited by the extremely large lagoons used for fishing and as sources of drinking water; however, starting in August 2014, an innovative technique of applying temephos to smaller cordoned sections of the lagoons at entry points used by infected humans or dogs was introduced and used to protect 19 villages in 2014 and 30 villages during January 2015–June 2015. The Carter Center and the WHO Collaborating Center for Dracunculiasis Eradication, Training, and Research at CDC are supporting research to better understand the unusual epidemiology of the current outbreak of dracunculiasis in Chad and assess antihelminthic treatment of dogs to prevent maturation of worms.

Ethiopia. In 2014, Ethiopia reported three cases of dracunculiasis (two contained) in three neighboring villages within Gog district in Gambella region, a reduction of 73% from the 11 cases reported in 2013. Three infected dogs and one infected baboon were also reported in the same area in 2014. During January–June 2015, one case (contained) and one infected dog were reported in the same area, compared with two cases and no infected dogs during the same period of 2014. Temephos was applied in all implicated villages within 7 days of identification of the case and infected animal. A total of 173 villages are under active surveillance in three districts of Gambella region with endemic disease. In October 2014, Ethiopia increased the amount of its cash reward for reporting a case to the equivalent of US$100.

Mali. Although no cases were reported during the first 6 months of 2014, in the remainder of 2014, Mali's Guinea Worm Eradication Program reported 40 cases (88% contained) in three villages in nomadic localities: Tanzikratene (29 cases) in Gao region, Nanguaye (10) in Timbuktu region, and Fion (one) in Segou region. These 40 cases represent a nearly fourfold increase over the 11 cases (64% contained) reported from eight villages in 2013. The first two villages have no source of safe drinking water; Fion has one safe source. Temephos was applied to surface water sources in all three localities soon after cases began to appear. More than 570 villages are under active surveillance, including the three villages that had cases in 2014, although the northern regions of Kidal, Gao, and Timbuktu are currently experiencing civil unrest and insecurity. In October 2014, Mali doubled its cash reward to the equivalent of US$100 for reporting a case. As in 2014, no cases were reported during the first 6 months of 2015.

South Sudan. The South Sudan Guinea Worm Eradication Program reported 70 cases of dracunculiasis in 2014, of which 47 (67%) were contained (Table 1), representing a 38% reduction from the 113 cases reported in 2013. During January–June 2015, only one case (contained) was provisionally reported, compared with 19 cases (79% contained) reported from 13 villages during January–June 2014, a 95% reduction in cases and a 92% decrease in villages reporting cases (Table 2). During November 2014–May 2015, South Sudan reported zero cases. As previously described (4), movements of persons along multiple routes for seasonal activities such as livestock grazing and farming, sporadic insecurity created during interethnic cattle raiding, and other factors have presented unusually complex challenges to this program. In addition, civil unrest and insecurity that began in December 2013 continued into 2015, although the area in Eastern Equatoria state with the highest endemicity was less affected by the insecurity, and coverage with interventions against transmission of dracunculiasis remains high (Table 1). In April 2014, South Sudan introduced a cash reward equivalent to about US$125 for reporting a case of dracunculiasis and achieved 82% awareness of the reward by the end of that year (9).

Discussion

In 2014, the 126 dracunculiasis cases reported through the global Guinea Worm Eradication Program were the lowest number ever reported, and reports from the first half of 2015 suggest that the total cases in 2015 might be even lower. Ghana, which once reported the second highest number of cases among all affected countries, was certified free of dracunculiasis transmission in January 2015. Despite facing major challenges, South Sudan has reported only one case in July 2015, compared with 22 in July 2014 and, as a result of the strong political support and technical leadership of the South Sudanese program, is on track to become the first among the last four endemic countries to interrupt transmission.

However, considerable challenges remain. The civil unrest and insecurity in Mali and South Sudan and the unusual epidemiology occurring in Chad represent the greatest challenges facing the global campaign. The sporadic infections in dogs and baboons in Ethiopia are not unprecedented; both these infections and those in humans seem to be declining.

Although the goals from the 1991 and 2004 World Health Assemblies to eradicate dracunculiasis globally in 1995 and 2009, respectively, were not achieved (6,10), considerable progress toward eradication has been made since 1986. This progress continued with a modest decrease in cases from 2013 to 2014, and was followed by a 70% decrease in cases during the first 6 months of 2015 compared with the same period in 2014. In 2014, 79% of cases occurred during the second half of the year, largely because of the outbreaks in South Sudan during July–August and in Mali during September–November. From 2013 to 2014, and during January–June 2014 and the same period during 2015, the number of villages reporting endemic cases in these four countries decreased by >50%.

Surveillance is a challenge everywhere dracunculiasis exists, and since March 2012, has been especially weak in dracunculiasis-affected areas of Mali because of civil unrest and insecurity. With sufficient attention to nationwide surveillance, including use of cash rewards for reports of rumors of possible cases, prompt containment of any infections, appropriate interventions, strong political support, and adequate security in the four remaining endemic countries (Chad, Ethiopia, Mali, and South Sudan), dracunculiasis will likely become the first parasitic disease to be eradicated.

1The Carter Center, Atlanta, Georgia; 2Division of Parasitic Diseases and Malaria, Center for Global Health, CDC; 3Division of Foodborne, Waterborne, and Environmental Diseases, National Center for Emerging and Zoonotic Infectious Diseases and World Health Organization Collaborating Center for Research, Training, and Eradication of Dracunculiasis, CDC.

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

References

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