Guinea Worm Eradication Program Research Articles

Progress Toward Global Dracunculiasis (Guinea Worm Disease) Eradication, January 2023-June 2024.

The effort to eradicate Dracunculus medinensis, the etiologic agent of dracunculiasis, or Guinea worm disease, began at CDC in 1980. In 1986, with an estimated 3.5 million global cases in 20 African and Asian countries, the World Health Assembly called for dracunculiasis elimination. The Guinea Worm Eradication Program (GWEP) was established to help countries with endemic dracunculiasis reach this goal. GWEP is led by The Carter Center and supported by partners, including the countries with endemic disease, CDC, UNICEF, and the World Health Organization. Since 2012, infections in dogs, cats, and baboons have posed a new challenge for GWEP, as have ongoing civil unrest and insecurity in some areas. As of June 2024, dracunculiasis remained endemic in five countries (Angola, Chad, Ethiopia, Mali, and South Sudan). Fourteen human cases and 886 animal infections occurred, including 407 dogs in Chad and 248 dogs in Cameroon, reported in 2023, and three human cases and 297 animal infections reported during January-June 2024. Animal infections, primarily in dogs in Cameroon and Chad, and impeded access due to civil unrest and insecurity in Mali, threaten the near-term possibility of global eradication. Nevertheless, countries appear poised to reach zero cases.

Cutaneous myiasis by Calliphoridae dipterans in dogs from Chad

Cutaneous myiasis caused by various Calliphoridae dipteran species is prevalent worldwide and is of particular veterinary and public health concern. Recently, in a scientific exploration of the Guinea Worm Eradication Program to Chad, Africa, we observed that dogs with mutilated ears, based on local awareness, were caused by cutaneous myiasis. In this study, we analyzed epidemiological, morphological, and molecular data on cutaneous myiasis in dogs from Chad. From September to October 2022, dogs (n = 1,562) from 56 villages situated along the Chari River were physically inspected for cutaneous myiasis. All larvae were collected and identified morphologically and by molecular analysis of the partial cytochrome oxidase c subunit I (COI) mitochondrial gene. The prevalence of myiasis infestation along with 95% confidence intervals (95% CI) was determined using the modified Wilson method. Myiasis was detected in dogs from 21 villages (37.5%; 95% CI 26 - 50%), predominating in the southernmost region. Of 1,562 dogs, 66 (4.22%; 95% CI 3.34 - 5.34%) were infested by calliphorid larvae, with a mean infestation of 2.28 larvae per animal (range = 1 to 24). Specimens were morphologically identified as Cordylobia anthropophaga (n = 94), Chrysomya bezziana (n = 54), and Chrysomya sp. (n = 3), which were detected in 57, eight and one dog, respectively. No co-infestations were observed. The molecular analyses confirmed the morphological identification and revealed the presence of 17 haplotypes for C. anthropophaga, 2 for C. bezziana, and one for Chrysomya sp. Our study emphasizes the veterinary importance of myiasis in dogs in Africa and proposes measures to assure their health and well-being.

Predicting the Environmental Suitability and Identifying Climate and Sociodemographic Correlates of Guinea Worm (Dracunculus medinensis) in Chad.

A comprehensive understanding of the spatial distribution and correlates of infection are key for the planning of disease control programs and assessing the feasibility of elimination and/or eradication. In this work, we used species distribution modeling to predict the environmental suitability of the Guinea worm (Dracunculus medinensis) and identify important climatic and sociodemographic risk factors. Using Guinea worm surveillance data collected by the Chad Guinea Worm Eradication Program (CGWEP) from 2010 to 2022 in combination with remotely sensed climate and sociodemographic correlates of infection within an ensemble machine learning framework, we mapped the environmental suitability of Guinea worm infection in Chad. The same analytical framework was also used to ascertain the contribution and influence of the identified climatic risk factors. Spatial distribution maps showed predominant clustering around the southern regions and along the Chari River. We also identified areas predicted to be environmentally suitable for infection. Of note are districts near the western border with Cameroon and southeastern border with Central African Republic. Key environmental correlates of infection as identified by the model were proximity to permanent rivers and inland lakes, farmlands, land surface temperature, and precipitation. This work provides a comprehensive model of the spatial distribution of Guinea worm infections in Chad 2010-2022 and sheds light on potential environmental correlates of infection. As the CGWEP moves toward elimination, the methods and results in this study will inform surveillance activities and help optimize the allocation of intervention resources.

Slaying the Serpent: A Research Agenda to Expand Intervention Development and Accelerate Guinea Worm Eradication Efforts.

Dracunculiasis, also known as Guinea worm disease, is targeted to become the second human disease and first parasitic infection to be eradicated. The global Guinea Worm Eradication Program (GWEP), through community-based interventions, reduced the burden of disease from an estimated 3.5 million cases per year in 1986 to only 13 human cases in 2022. Despite progress, in 2012 Guinea worm disease was detected in domesticated dogs and later in domesticated cats and baboons. Without previous development of any Guinea worm therapeutics, diagnostic tests to detect pre-patent Guinea worm infection, or environmental surveillance tools, the emergence of Guinea worm disease in animal hosts-a threat to eradication-motivated an assessment of evidence gaps and research opportunities. This gap analysis informed the refinement of a robust research agenda intended to generate new evidence and identify additional tools for national GWEPs and to better align the global GWEP with a 2030 Guinea worm eradication certification target. This paper outlines the rationale for the development and expansion of the global GWEP Research Agenda and summarizes the results of the gap analysis that was conducted to identify Guinea worm-related research needs and opportunities. We describe five work streams informed by the research gap analysis that underpin the GWEP Research Agenda and address eradication endgame challenges through the employment of a systems-informed One Health approach. We also discuss the infrastructure in place to disseminate new evidence and monitor research results as well as plans for the continual review of evidence and research priorities.

Dracunculiasis over the centuries: the history of a parasite unfamiliar to the West.

Dracunculiasis (Guinea Worm Disease) is a terrible disease limited, even historically, to the arid and poor areas of our planet and which in the West has always been seen as an exotic disease and therefore has never taken root in the collective imagination. This parasitosis is transmitted to humans by drinking water contaminated with crustacean harboring larvae of Dracunculus medinensis, a nematode. The natural history of the disease is caused by adult worms invading connective tissues and causing blistering, ulceration and edema. Well known in Ancient Egypt where the disease was endemic in its southern area, was known in Europe mainly from the reports of medical writers starting from the Roman imperial period but without direct knowledge. In Middle age the descriptions of this disease that physicians and surgeons could read on medical books, at the end, were attributed to veterinary parasitic disease. In Modern age only during the colonialist era dracunculiasis was perceived as a problem, however sporadic. In 1986 Guinea Worm Eradication Program (GWEP) was launch without success. Thus, the disappearance of this parasitosis should still be postponed but not abandoned.

Epidemiological Analysis of the 2019 Dracunculiasis Outbreak in the Liwi Area, Salamat Province (Chad): Evidence of the Role of Pets

Aims: Dracunculiasis is a neglected disease caused by a parasitic nematode, Dracunculus medinensis, also called the filaria of Medina. An outbreak of this disease occurred in the Salamat province in Chad in 2019, while the eradication of this disease worldwide was in its final stage. The outbreak occurred in the Bogam village (Liwi area), where this disease has never been reported in the past. The present work is aimed at identifying the factors that would have favored that outbreak, and the constraints that delay the eradication of dracunculiasis in Chad.
 Study Design: Retrospective study.
 Place and Duration of Study: The data retrospectively analyzed are those recorded during the census of patients by the Chadian National Guinea Worm Eradication Program (PEVG), from 2019 to 2020, and supplemented by those contained in the registers of previous years. The analyzes were carried out in N'Djamena, between July and November 2021, within the Laboratory of the Faculty of Medicine.
 Methodology: The census of patients was carried out during a survey from 2019 to 2020 by PEVG. These data have been supplemented by those contained in the registers of previous years. Data were first stored in a Microsoft (Excel 2007 Software) spreadsheet, then transferred to the SPSS version 20.0 Software, after removal of outliers and input errors. The Chi-Square test (χ2) made it possible to compare the percentages at the threshold of p<0.005.
 Results: In summary it appeared that 52.4% of the patients were 5 to 20 years old, 62% were female, 90.48% lived in Bogam, 95.2% used dirty water from ponds and traditional wells, 33% were farmers, and 33% were breeders. In addition, most of the patients became infected between March and November 2018. The following risk factors combined could explain the Bogam 2019 dracunculiasis outbreak namely: cohabitation with infested pets coming into contact with water, the behavior of young and active people with respect to water, consumption of unhygienic water, gender, lack of containment of some patients that could enter water barefoot, period extending from April to September.
 Conclusion: This work highlighted the obvious role of pets as a reservoir on the one hand, and the effectiveness of the PEVG in the fight against dracunculiasis through a treatment protocol combining a wet bandage associated with oral diclofenac + amoxicillin + paracetamol.

Progress Toward Global Eradication of Dracunculiasis - Worldwide, January 2021-June 2022.

Dracunculiasis (Guinea worm disease), caused by the parasite Dracunculus medinensis, is acquired by drinking water containing small crustacean copepods (water fleas) infected with D. medinensis larvae. Recent evidence suggests that the parasite also appears to be transmitted by eating fish or other aquatic animals. About 1 year after infection, the worm typically emerges through the skin on a lower limb of the host, causing pain and disability (1). No vaccine or medicine is available to prevent or treat dracunculiasis. Eradication relies on case containment* to prevent water contamination and other interventions to prevent infection, including health education, water filtration, treatment of unsafe water with temephos (an organophosphate larvicide), and provision of safe drinking water (1,2). CDC began worldwide eradication efforts in October 1980, and in 1984 was designated by the World Health Organization (WHO) as the technical monitor of the Dracunculiasis Eradication Program (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. The Guinea Worm Eradication Program (GWEP),¶ led by The Carter Center and supported by partners that include WHO, UNICEF, and CDC, began assisting ministries of health in countries with endemic disease. In 2021, a total of 15 human cases were identified and three were identified during January-June 2022. As of November 2022, dracunculiasis remained endemic in five countries (Angola, Chad, Ethiopia, Mali, and South Sudan); cases reported in Cameroon were likely imported from Chad. Eradication efforts in these countries are challenged by infection in animals, the COVID-19 pandemic, civil unrest, and insecurity. Animal infections, mostly in domestic dogs, some domestic cats, and in Ethiopia, a few baboons, have now surpassed human cases, with 863 reported animal infections in 2021 and 296 during January-June 2022. During the COVID-19 pandemic all national GWEPs remained fully operational, implementing precautions to ensure safety of program staff members and community members. In addition, the progress toward eradication and effectiveness of interventions were reviewed at the 2021 and 2022 annual meetings of GWEP program managers, and the 2021 meeting of WHO's International Commission for the Certification of Dracunculiasis Eradication. With only 15 human cases identified in 2021 and three during January-June 2022, program efforts appear to be closer to reaching the goal of eradication. However, dog infections and impeded access because of civil unrest and insecurity in Mali and South Sudan continue to be the greatest challenges for the program. This report describes progress during January 2021-June 2022 and updates previous reports (2,4).

Using point-of-view cameras (Crittercams) to document potential risk behaviors for Guinea worm (Dracunculus medinensis) transmission in domestic cats in Chad, Africa

Guinea worm (Dracunculus medinensis) infection has historically been a concern for humans, with parasite transmission occurring through drinking water containing infected cyclopoid copepods. However, infections in domestic dogs and cats in Chad, Africa increased between 2015 and 2021, and the epidemiology of these infections suggests that parasite transmission may also occur through ingestion of infected paratenic and transport hosts such as fish, reptiles, and amphibians. While previous work has examined transmission in domestic dogs, little is known about routes of transmission in domestic cats. In this study, we used animal-borne video cameras (Crittercams) provided by National Geographic’s Exploration Technology Lab to document the nighttime behaviors of domestic cats in Chad. Our objective was to identify cat and human behaviors that may be contributing to Guinea worm transmission. Cameras were deployed on 11 owned cats in August 2018 and videos were examined to identify risky behaviors, including stalking and capturing prey, scavenging, being fed by humans, and drinking water. Guinea worm infection data for individual cats was collected from owners; infection data for each village was collected from the Chadian National Guinea Worm Eradication Program (GWEP). Nine cats were observed eating items such as insects, fish, amphibians, reptiles, rodents, and millet-based grain balls; 8 cats were observed scavenging; 6 cats were observed stalking and capturing prey; 4 cats were observed being fed fish or grain balls by humans; and 5 cats were observed drinking water. Cats demonstrated risky behaviors on 14 of the 17 recorded nights and 10 of the 11 enrolled cats demonstrated at least one risky behavior. Cats were observed engaging in risky behaviors between 0 and 20 times per night: cats scavenged up to 11 times per night, ate up to 10 times per night, and hunted up to four prey items per night. Three of the enrolled cats were owner-reported to have a previous Guinea worm infection; one cat infection per village was reported to the GWEP. Overall, we successfully used Crittercams to document behaviors that could be associated with Guinea worm transmission in cats. Additional work is needed to determine the role of these behaviors in transmission of D. medinensis, and specifically, whether behaviors within the household increase opportunities for transmission to cats.

Development and validation of a quantitative PCR for the detection of Guinea worm (Dracunculus medinensis).

Dracunculus medinensis (Guinea worm) is a parasitic nematode that can cause the debilitating disease dracunculiasis (Guinea worm disease) in humans. The global Guinea Worm Eradication Program has led intervention and eradication efforts since the 1980s, and Guinea worm infections in people have decreased >99.99%. With the final goal of eradication drawing nearer, reports of animal infections from some remaining endemic countries pose unique challenges. Currently, confirmation of suspected Guinea worm infection relies on conventional molecular techniques such as polymerase chain reaction (PCR), which is not specific to Guinea worm and, therefore, requires sequencing of the PCR products to confirm the identity of suspect samples, a process that often takes a few weeks. To decrease the time required for species confirmation, we developed a quantitative PCR assay targeting the mitochondrial cytochrome b (cytb) gene of Guinea worm. Our assay has a limit of detection of 10 copies per reaction. The mean analytical parameters (± SE) were as follows: efficiency = 93.4 ± 7.7%, y-intercept = 40.93 ± 1.11, slope = -3.4896 ± 0.12, and the R2 = 0.999 ± 0.004. The assay did not amplify other nematodes found in Guinea worm-endemic regions and demonstrated 100% diagnostic sensitivity and specificity. Implementation of this quantitative PCR assay for Guinea worm identification could eliminate the need for DNA sequencing to confirm species. Thus, this approach can be implemented to provide more rapid confirmation of Guinea worm infections, leading to faster execution of Guinea worm interventions while increasing our understanding of infection patterns.

Effects of Temephos (Abate®), Spinosad (Natular®), and Diflubenzuron on the Survival of Cyclopoid Copepods.

ABSTRACT.Dracunculus medinensis, also known as the African Guinea worm, is the causative agent of dracunculiasis and the focus of the global Guinea Worm Eradication Program (GWEP). Transmission of D. medinensis to humans occurs primarily by drinking water containing cyclopoid copepods infected with third-stage D. medinensis larvae. A common intervention to interrupt transmission and decrease the number of copepods in infected water bodies is the application of the organophosphate larvicide Abate® (temephos). However, the use of alternative compounds to help decrease copepod populations would be beneficial to the GWEP. We compared the immobilization of copepods by three compounds: Abate, Natular® (spinosad), and diflubenzuron. Our results confirm that neither diflubenzuron nor Natular immobilized copepods as quickly or as effectively as Abate. However, doubling or tripling the suggested concentration of Natular resulted in immobilization rates similar to Abate over 72 hours of continuous exposure. Further research on the possible effects of higher concentrations of Natular on the environment and nontarget organisms is necessary to determine whether this compound can be used safely to control the copepod population.

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).

Assessment of the Chad guinea worm surveillance information system: A pivotal foundation for eradication.

In the absence of a vaccine or pharmacological treatment, prevention and control of Guinea worm disease is dependent on timely identification and containment of cases to interrupt transmission. The Chad Guinea Worm Eradication Program (CGWEP) surveillance system detects and monitors Guinea worm disease in both humans and animals. Although Guinea worm cases in humans has declined, the discovery of canine infections in dogs in Chad has posed a significant challenge to eradication efforts. A foundational information system that supports the surveillance activities with modern data management practices is needed to support continued program efficacy. We sought to assess the current CGWEP surveillance and information system to identify gaps and redundancies and propose system improvements. We reviewed documentation, consulted with subject matter experts and stakeholders, inventoried datasets to map data elements and information flow, and mapped data management processes. We used the Information Value Cycle (IVC) and Data-Information System-Context (DISC) frameworks to help understand the information generated and identify gaps. Findings from this study identified areas for improvement, including the need for consolidation of forms that capture the same demographic variables, which could be accomplished with an electronic data capture system. Further, the mental models (conceptual frameworks) IVC and DISC highlighted the need for more detailed, standardized workflows specifically related to information management. Based on these findings, we proposed a four-phased roadmap for centralizing data systems and transitioning to an electronic data capture system. These included: development of a data governance plan, transition to electronic data entry and centralized data storage, transition to a relational database, and cloud-based integration. The method and outcome of this assessment could be used by other neglected tropical disease programs looking to transition to modern electronic data capture systems.

Surveillance of Human Guinea Worm in Chad, 2010-2018.

.The total number of Guinea worm cases has been reduced by 99.9% since the mid-1980s when the eradication campaign began. Today, the greatest number of cases is reported from Chad. In this report, we use surveillance data collected by the Chad Guinea Worm Eradication Program to describe trends in human epidemiology. In total, 114 human cases were reported during the years 2010–2018, with highest rates of containment (i.e., water contamination prevented) in the years 2013, 2014, 2016, and 2017 (P < 0.0001). Approximately half of case-patients were female, and 65.8% of case-patients were aged 30 years or younger (mean: 26.4 years). About 34.2% of case-patients were farmers. Cases were distributed across many ethnicities, with a plurality of individuals being of the Sara Kaba ethnicity (21.3%). Most cases occurred between the end of June and the end of August and were clustered in the Chari Baguirmi (35.9%) and Moyen Chari regions (30.1%). Cases in the northern Chari River area peaked in April and in August, with no clear temporal pattern in the southern Chari River area. History of travel within Chad was reported in 7.0% of cases, and male case-patients (12.5%) were more likely than female case-patients (1.7%) to have reported a history of travel (P = 0.03). Our findings confirm that human Guinea worm is geographically disperse and rare. Although the proportion of case-patients with travel history is relatively small, this finding highlights the challenge of surveillance in mobile populations in the final stages of the global eradication campaign.

Correlates of Variation in Guinea Worm Burden among Infected Domestic Dogs.

ABSTRACTThe Guinea Worm Eradication Program has been extraordinarily successful—in 2019, there were 53 human cases reported, down from the estimated 3.5 million in 1986. Yet the occurrence of Guinea worm in dogs is a challenge to eradication efforts, and underlying questions about transmission dynamics remain. We used routine surveillance data to run negative binomial regressions predicting worm burden among infected dogs in Chad. Of 3,371 infected dogs reported during 2015–2018, 38.5% had multiple worms. A multivariable model showed that the number of dogs in the household was negatively associated with worm burden (adjusted incidence rate ratio [AIRR] = 0.95, 95% CI: 0.93–0.97, P < 0.0001) after adjusting for dog age (AIRR = 0.99, 95% CI: 0.96–1.01, P > 0.1). This could relate to the amount of infective inocula (e.g., contaminated food or water) shared by multiple dogs in a household. Other significant univariable associations with worm burden included dog history of Guinea worm infection (IRR = 1.30, 95% CI: 1.18–1.45) and dog owners who were hunters (IRR = 0.78, 95% CI: 0.62–0.99, P < 0.05) or farmers (IRR = 0.83, 95% CI: 0.77–0.90, P < 0.0001). Further analysis showed that the number of dogs in the household was significantly and positively correlated with nearly all other independent variables (e.g., owner occupation: farmer, fisherman, or hunter; dog age, sex, and history of Guinea worm). The associations we identified between worm burden and dogs per household, and dogs per household and owner characteristics should be further investigated with more targeted studies.

Development of a Multiplex Bead Assay for the Detection of Canine IgG4 Antibody Responses to Guinea Worm.

Increased levels of guinea worm (GW) disease transmission among dogs in villages along the Chari River in Chad threaten the gains made by the GW Eradication Program. Infected dogs with preemergent worm blisters are difficult to proactively identify. If these dogs are not contained, blisters can burst upon submersion in water, leading to the contamination of the water supply with L1 larvae. Guinea worm antigens previously identified using sera from human dracunculiasis patients were coupled to polystyrene beads for multiplex bead assay analysis of 41 non-endemic (presumed negative) dog sera and 39 sera from GW-positive dogs from Chad. Because commercially available anti-dog IgG secondary antibodies did not perform well in the multiplex assay, dog IgGs were partially purified, and a new anti-dog IgG monoclonal antibody was developed. Using the new 4E3D9 monoclonal secondary antibody, the thioredoxin-like protein 1-glutathione-S-transferase (GST), heat shock protein (HSP1)-GST, and HSP2-GST antigen multiplex assays had sensitivities of 69-74% and specificities of 73-83%. The domain of unknown function protein 148 (DUF148)-GST antigen multiplex assay had a sensitivity of 89.7% and a specificity of 85.4%. When testing samples collected within 1 year of GW emergence (n = 20), the DUF148-GST assay had a sensitivity of 90.0% and a specificity of 97.6% with a receiver-operating characteristic area under the curve of 0.94. Using sera from two experimentally infected dogs, antibodies to GW antigens were detected within 6 months of exposure. Our results suggest that, when used to analyze paired, longitudinal samples collected 1-2 months apart, the DUF148/GST multiplex assay could identify infected dogs 4-8 months before GW emergence.

A Point Source Outbreak of &lt;i&gt;Dracunculus Medinensis&lt;/i&gt; Affecting Both Humans and Dogs -- Chad, 2019

Background: Guinea worm is on the verge of eradication, with a 99.9% reduction in cases since the mid-1980s. Most cases now occur Chad. On April 19, 2019, a 19-year-old woman presented with a Guinea worm in Salamat Region, Chad, an area where the disease had not been previously reported. Methods: We conducted a field investigation including household case searches and informal group interviews. Four mitochondrial genes and 22 nuclear microsatellite markers were used to assess relatedness of worms associated with the outbreak in comparison with other worms from elsewhere in Chad. Findings: We identified 22 human cases and 2 canine cases. Most human case-patients were from three villages in Salamat, but one case-patient was detected nearly 400km away in Sarh city. All case-patients reported a history of consuming fish and unfiltered water. Community members recalled a dog in 2018 with a Guinea worm-like infection (undetected by the surveillance system) that could have been the source of water contamination that ultimately seeded the 2019 outbreak. Worms associated with this outbreak were genetically similar and shared the same maternal lineage. Interpretation: Molecular epidemiologic results suggested a point-source outbreak that originated from a single female Guinea worm, rather than newly identified sustained local transmission. The unusually long 147-day duration of this outbreaks suggests the possible involvement of a paratenic host. This outbreak affected both humans and dogs, illustrating the importance of prevention and control of Guinea worm in dogs as a continued focus for eradication efforts. Funding: The Carter Center. Declaration of Interest: None to declare Ethical Approval: Approval for this analysis was granted by the Chad Ministry of Public Health (MOPH), and a non-research determination was granted by the delegated authority at the U.S. Centers for Disease Control and Prevention (CDC). Investigation methods employed are a part of routine outbreak response protocols as defined by the Chad Guinea Worm Eradication Program (CGWEP, which is a part of the MOPH).

Progress Toward Global Eradication of Dracunculiasis, January 2019-June 2020.

Dracunculiasis (Guinea worm disease) is caused by the parasite Dracunculus medinensis and is acquired by drinking water containing copepods (water fleas) infected with D. medinensis larvae. The worm typically emerges through the skin on a lower limb approximately 1 year after infection, resulting in pain and disability (1). There is no vaccine or medicine to treat the disease; eradication efforts rely on case containment* to prevent water contamination. Other interventions to prevent infection include health education, water filtration, chemical treatment of unsafe water with temephos (an organophosphate larvicide to kill copepods), and provision of safe drinking water (1,2). The worldwide eradication campaign began in 1980 at CDC (1). In 1986, with an estimated 3.5 million cases† occurring each year in 20 African and Asian countries§ (3), the World Health Assembly (WHA) called for dracunculiasis elimination (4). The global Guinea Worm Eradication Program (GWEP), led by the Carter Center and supported by the World Health Organization (WHO), United Nations Children's Fund, CDC, and other partners, began assisting ministries of health in countries with dracunculiasis. This report, based on updated health ministry data (4), describes progress made during January 2019-June 2020 and updates previous reports (2,4,5). With only 54 human cases reported in 2019, 19 human cases reported during January 2019-June 2020, and only six countries currently affected by dracunculiasis (Angola, Chad, Ethiopia, Mali, South Sudan, and importations into Cameroon), the achievement of eradication is within reach, but it is challenged by civil unrest, insecurity, and lingering epidemiologic and zoologic concerns, including 2,000 reported animal cases in 2019 and 1,063 animal cases in 2020, mostly in dogs. All national GWEPs remain fully operational, with precautions taken to ensure safety of program staff members and community members in response to the coronavirus disease 2019 (COVID-19) pandemic.

Challenges in the last mile of the global guinea worm eradication program.

The objective of this study was to identify the existing challenges in the last mile of the global Guinea Worm Eradication Program. Systematic Review of articles published from 1 January 2000 until 31 December 2019. Papers listed in Cochrane Library, Google Scholar, ProQuest PubMed and Web of Science databases were searched and reviewed. Twenty-five articles met inclusion criteria of the study and were selected for analysis. Hence, relevant data were extracted, grouped and descriptively analysed. Results revealed 10 main challenges complicating the last mile of global guinea worm eradication: unusual mode of transmission; rising animal guinea worm infection; suboptimal surveillance; insecurity; inaccessibility; inadequate safe water points; migration; poor case containment measures, ecological changes; and new geographic foci of the disease. This systematic review shows that most of the current challenges in guinea worm eradication have been present since the start of the campaign. However, the recent change in epidemiological patterns and nature of dracunculiasis in the last remaining endemic countries illustrates a new twist. Considering the complex nature of the current challenges, there seems to be a need for a more coordinated and multidisciplinary approach of dracunculiasis prevention and control measures. These new strategies would help to make history by eradicating dracunculiasis as the first ever parasitic disease.

Dracunculus Species in Meso-mammals from Georgia, United States, and Implications for the Guinea Worm Eradication Program in Chad, Africa.

The prevalence and diversity of parasitic nematodes in wildlife have been well studied for certain species, yet for others considerable gaps in knowledge exist. The parasitic nematode Dracunculus insignis infects North American wildlife, and past research on this species has led to an increased understanding of the potential host diversity and transmission of the closely related human Guinea worm, Dracunculus medinensis (which is currently the focus of a global eradication program). Many definitive hosts have been documented for D. insignis; however, the life cycle has been studied only in laboratories, and only a single phylogenetic study has been conducted on D. insignis (from Canada). The goals of the present study were to investigate the prevalence of infections with Dracunculus species among wildlife at a single site (Di-Lane plantation) in the southeastern United States, evaluate the genetic diversity of parasites at this site, and investigate potential paratenic hosts that may be involved in transmission. Over 3 yr, we sampled 228 meso-mammals, reporting an overall prevalence of infection with Dracunculus insignis of 20% (46/228). Amphibians and fish were sampled in the same geographic area as infected meso-mammals. Dracunculus insignis third-stage larvae were recovered from 2 different species of amphibians, but all fish sampled were negative. Phylogenetic analysis of the partial cytochrome c oxidase I (COI) gene showed very little diversity of Dracunculus at Di-Lane; however, we did recover a single nematode from a Virginia opossum (Didelphis virginiana) that falls outside of the D. insignis clade, more closely aligns with Dracunculus lutrae, and may represent an undescribed species. This work documents the occurrence of D. insignis in frogs, a potential transmission pathway for D. insignis at a single geographic site in nature. When applied to the global Guinea Worm Eradication Program, and Chad, Africa, in particular, this work increases our knowledge of the potential role of aquatic animals in the transmission of Dracunculus species and informs on potential intervention strategies that may be applied to the eradication of Guinea worm in Africa.

Development of a Multiplex Bead Assay for the Detection of IgG Antibody Responses to Guinea Worm.

The success of the Guinea Worm (GW) Eradication Program over the past three decades has been tempered by the persistence of GW disease in a few African nations and the potential for a future resurgence in cases. Domestic dogs are now a major concern as a disease reservoir as large numbers of cases of canine GW disease are now reported each year, mainly along the Chari River in Chad. As a first step toward the development of a serologic assay for dogs, archived human plasma samples from dracunculiasis-positive donors from Togo were used to select adult female GW antigens for peptide sequencing and cloning. Eight protein sequences of interest were expressed as recombinant glutathione-S-transferase (GST) fusion proteins, and the most promising proteins were coupled to carboxylated microspheres for use in multiplex assays. A thioredoxin-like protein (TRXL1) and a domain of unknown function (DUF148) were assessed for total IgG and IgG4 reactivities using a panel of specimens from GW cases, uninfected donors, and individuals infected with various nematode worms, including Onchocerca volvulus. Both the DUF148-GST and the TRXL1-GST assays cross-reacted with O. volvulus sera, but the latter assay was always the more specific. The IgG4 and total IgG TRXL1-GST assays both had sensitivities > 87% and specificities > 90%. Maximum specificity (> 96%) was obtained with the total IgG assay when reactivity to both antigens was used to define a positive case. Given the good performance of the human assay, we are now working to modify the assay for dog assessments.