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Introduction: Guinea worm disease is caused by Dracunculus medinensis. Transmission of the disease depends on vectors (copepods). Abate applications in targeted water sources to control copepod is the main intervention. The aim of this study was to assess vector control practice in the guinea worm endemic region of Gambela, Ethiopia and to identify elimination gaps. Methodology: Retrospective analysis of routine program data recorded from 2016 to 2020 was performed. Pre-and post-copepod test is conducted on water ponds to determine the density of copepods. Based on the copepod density, the chemical is applied accordingly. The five years data was obtained from Ethiopian public health institute electronic database with permission. Results: A total of 22,131 water ponds were treated during the past five years. Out of the total treated in 2020, 4,669/7,266 (64%) were found with > 9 Copepods during pre-copepod test. 130/7,266 (1.79%) of water ponds which were post-tested after Abate application failed the requirement of scoring ≤ 9 copepods. Of the 130 water ponds, 115 (88.5%) were observed during the transmission season (April to November). Abate application trend had increased by 28.9% during the 5 years period. According to the database, some of the largest water sources found in infection reporting villages missed their 28 days regular treatment schedule. Conclusions: A single water source that has not been treated effectively could be a source of infection for both humans and animals. The practice of Abate application should be enhanced and monitored regularly. The documenting system should be improved for quality, timely information and action.

Summary Background Dracunculiasis (also known as Guinea worm disease), caused by the Dracunculus medinensis nematode, is progressing towards eradication, with a reduction in cases from 3·5 million cases in the mid-1980s to only 54 human cases at the end of 2019. Most cases now occur in Chad. On April 19, 2019, a 19-year-old woman presented with D medinensis in an area within the Salamat region of Chad, where the disease had not been previously reported. We aimed to investigate the connection between this case and others detected locally and elsewhere in Chad using a combination of epidemiological and genetic approaches. Methods In this cross-sectional field study, we conducted household case searches and informal group interviews in the Bogam, Liwi, and Tarh villages in Chad. All community members including children were eligible for participation in the outbreak investigation. Adult female D medinensis associated with this outbreak were collected for genetic analysis (18 from humans and two from dogs). 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 Between April 12 and Sept 6, 2019, we identified 22 human cases and two canine cases of dracunculiasis associated with 15 households. Six (40%) of the 15 affected households had multiple human or canine cases within the household. Most cases of dracunculiasis in people were from three villages in Salamat (21 [95%] of 22 cases), but one case was detected nearly 400 km away in Sarh city (outside the Salamat region). All people with dracunculiasis reported a history of consuming fish and unfiltered water. Worms associated with this outbreak were genetically similar and shared the same maternal lineage. Interpretation Molecular epidemiological results suggest a point-source outbreak that originated from a single female D medinensis, rather than newly identified sustained local transmission. The failure of the surveillance system to detect the suspected canine infection in 2018 highlights the challenge of canine D medinensis detection, particularly in areas under passive surveillance. Human movement can also contribute to dracunculiasis spread over long distances. Funding The Carter Center.

Domestic dogs have an important role in the ecology of transmission of the Guinea worm, a debilitating human parasite. A new study documents how fish content in dogs' diets can predict Guinea worm infection status, suggesting additional avenues for control.

The global Guinea worm eradication program represents one of the great public health success stories of our time. Since the program’s inception in 1980, the number of annual human cases has reduced by 99.9%, from an estimated 3.5 million cases in 21 countries1 to only 54 cases in three countries at the end of 2019.2,3 Causing significant disability and pain, Guinea worm infection occurs through the ingestion of freshwater copepods (small water crustaceans) infected with stage 3 Dracunculus medinensis larvae. After approximately 10–14 months, a blister forms (usually on a lower limb) where the pregnant adult female Guinea worm ruptures the skin.4 Upon detection of a possible Guinea worm case, patients are transported to health centers where they receive care. The worm is extracted via “controlled immersion,” in which the wound is submerged in a water-filled container to induce worm emergence without the risk of contaminating public water sources.5 Guinea worm is a disease of poverty, primarily impacting people in remote areas who do not have access to safe water for drinking and are forced to drink from stagnant water sources such as ponds, pools, and unprotected open wells that may contain infected copepods.5 The seasonality of disease incidence varies geographically owing to the timing of precipitation patterns and abundance of stagnant water sources.5 For example, in the Sahel (Mali, Niger, Chad), cases historically peaked in the months May through October when stagnant water sources are most abundant. Young adults (15–45 years of age) are most likely to be infected with D. medinensis, although persons of all ages can develop infection.5 Guinea worm cases have historically been equally distributed among men and women, though some exceptions have been noted.5 Occupation is an important risk factor; farmers and persons who fetch drinking water are commonly infected.5 In some countries (i.e., Mali, Niger, and Burkina Faso), certain ethnic groups are at higher risk of infection because of seasonal migration across long distances and, in some cases, the seasonal search for water or pasture for cattle.5 Conventional thought about Guinea worm transmission ecology was challenged in 2012 when canine cases were first reported in Chad in significant numbers,6 spurring new research on transmission dynamics. Today, Chad is the epicenter of D. medinensis transmission, reporting 88% of human cases (N = 48) and virtually all canine cases (99%, N = 1,927) worldwide in 2019.2,3,7 Recent case-control studies conducted in Chad have shown that water sources associated with increased risk for Guinea worm include lagoons, ponds, and untreated water from hand-dug wells.8,9 No associations have been observed to date between human Guinea worm and consumption of fish and frogs,9 which has been demonstrated in dogs.10 This is could be because humans are less likely than dogs to consume uncooked small fish/fingerlings and frogs, which can serve as transport or paratenic hosts.11,12 Over five years have passed since Eberhard et al.6 first described the unusual epidemiological patterns in Chad, noting that human cases are sporadic and rare in comparison with canine cases, with no apparent association with common water sources and no clustering by village. Since that time, the number of canine cases has generally increased steadily as surveillance expanded,2,3,13 whereas human cases have remained generally constant and at low numbers.2,3 Here, we use additional surveillance data to determine whether those epidemiologic patterns persist and to characterize in greater depth human Guinea worm in Chad, with the broader goal of furthering our understanding D. medinensis transmission and epidemiology.

Dracunculus spp. are parasitic nematodes that infect numerous species of mammals and reptiles. The life cycles of Dracunculus species are complex, and unknowns remain regarding the role of paratenic and transport hosts in transmission to definitive hosts. We had two primary objectives: to assess the susceptibility of several species of anurans, lizards, and fish as paratenic hosts for Dracunculus species, and to determine the long-term persistence of Dracunculus infections in African clawed frogs (Xenopus laevis). Animals were orally exposed to copepods infected with infectious third-stage larvae (L3s) of either Dracunculus insignis or D. medinensis. Dracunculus L3s were recovered from four anuran species, two lizard species, and one fish species, demonstrating that Dracunculus can infect tissues of a diversity of species. In long-term persistence trials, D. medinensis L3s were recovered from African clawed frogs tissues up to 58 days post-infection, and D. insignis L3s were recovered up to 244 days post-infection. Our findings regarding the susceptibility of novel species of frogs, lizards, and fish to infection with Dracunculus nematodes, and long-term persistence of L3s in paratenic hosts, address pressing knowledge gaps regarding Dracunculus infection in paratenic hosts and may guide future research regarding the transmission of Dracunculus to definitive mammalian hosts.

We report and discuss the surprising encounter of a dog naturally infected by Dracunculus sp. in Brazil, a brief clinical history of the animal and a procedure for removing the nematode. We also present details on the morphology of the fragments collected from the nematode and a phylogenetic comparison of the partial sequences of the mitochondrial 18S rRNA and cytochrome c oxidase subunit I (COI) genes, deposited with others in GenBank. The samples were an independent lineage forming a well-supported monophyletic assemblage with D. medinensis. We thus conclude that this species has not yet been sequenced or even described and will only be elucidated by more information because only two species of Dracunculus have been reported in Brazil, D. fuelleborni and D. brasiliensis.

Dracunculiasis, slated for global eradication, typically is acquired by drinking stagnant water containing microscopic crustaceans (copepods) infected with Dracunculus medinensis larvae, causing clusters of case persons with worms emerging from the skin. Following a 10-year absence of reported cases, 9–26 sporadic human cases with few epidemiologic links have been reported annually in Chad since 2010; dog infections have also been reported since 2012. We conducted an investigation of human cases in Chad to identify risk factors. We conducted a case–control study using a standardized questionnaire to assess water and aquatic animal consumption, and links to dog infections. Case persons had laboratory-confirmed D. medinensis during 2013–2017. Each case person was matched to one to three controls without history of disease by age, gender, and residency in the village where the case person was likely infected. We estimated odds ratios (ORs) using simple conditional logistic regression. We enrolled 25 case persons with 63 matched controls. Dracunculiasis was associated with consumption of untreated water from hand-dug wells (OR: 13.4; 95% CI: 1.7–108.6), but neither with consumption of aquatic animals nor presence of infected dogs in villages. Unsafe water consumption remains associated with dracunculiasis. Education of populations about consuming safe water and using copepod filters to strain unsafe water should continue and expand, as should efforts to develop and maintain safe drinking water sources. Nevertheless, the peculiar epidemiology in Chad remains incompletely explained. Future studies of dogs might identify other risk factors.

The 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.

The campaign to eradicate dracunculiasis (Guinea worm [GW] disease) and its causative pathogen Dracunculus medinensis (GW) in Chad is challenged by infections in domestic dogs, which far outnumber the dwindling number of human infections. We present an agent-based simulation that models transmission of GW between a shared water source and a large population of dogs. The simulation incorporates various potential factors driving the infections including external factors and two currently used interventions, namely, tethering and larvicide water treatments. By defining and estimating infectivity parameters and seasonality factors, we test the simulation model on scenarios where seasonal patterns of dog infections could be driven by the parasite’s life cycle alone or with environmental factors (e.g., temperature and rainfall) that could also affect human or dog behaviors (e.g., fishing versus farming seasons). We show that the best-fitting model includes external factors in addition to the pathogen’s life cycle. From the simulation, we estimate that the basic reproductive number, R0, is approximately 2.0; our results also show that an infected dog can transmit the infection to 3.6 other dogs, on average, during the month of peak infectivity (April). The simulation results shed light on the transmission dynamics of GWs to dogs and lay the groundwork for reducing the number of infections and eventually interrupting transmission of GW.

The global programme for the eradication of Guinea worm disease, caused by the parasitic nematode Dracunculus medinensis, has been successful in driving down human cases, but infections in non-human animals, particularly domestic dogs (Canis familiaris), now present a major obstacle to further progress. Dog infections have mainly been found in Chad and, to a lesser extent, in Mali and Ethiopia. While humans classically acquire infection by drinking water containing infected copepods, it has been hypothesized that dogs might additionally or alternatively acquire infection via a novel pathway, such as consumption of fish or frogs as possible transport or paratenic hosts. We characterized the ecology of free-ranging dogs living in three villages in Gog woreda, Gambella region, Ethiopia, in April-May 2018. We analysed their exposure to potential sources of Guinea worm infection and investigated risk factors associated with infection histories. The home ranges of 125 dogs and their activity around water sources were described using GPS tracking, and the diets of 119 dogs were described using stable isotope analysis. Unlike in Chad, where Guinea worm infection is most frequent, we found no ecological or behavioural correlates of infection history in dogs in Ethiopia. Unlike in Chad, there was no effect of variation among dogs in their consumption of aquatic vertebrates (fish or frogs) on their infection history, and we found no evidence to support hypotheses for this novel transmission pathway in Ethiopia. Dog owners had apparently increased the frequency of clean water provision to dogs in response to previous infections. Variations in dog ranging behaviour, owner behaviour and the characteristics of natural water bodies all influenced the exposure of dogs to potential sources of infection. This initial study suggests that the classical transmission pathway should be a focus of attention for Guinea worm control in non-human animals in Ethiopia.

Introduction The global Guinea Worm Eradication Program has reduced numbers of human infections of Guinea worm disease (dracunculiasis) to 49 cases in four countries. However, infections of domestic animals (dogs and cats) have recently been recognized and are increasing. Typically, Guinea worm (Dracunculus medinensis) transmission occurs via the ingestion of copepods from water. Despite several interventions, including tethering of dogs while worms emerge, the number of infected dogs continue to increase. One hypothesis is that dogs could be infected through the ingestion of copepods in provisioned water. Objectives The purpose of this study was to determine whether copepods can survive in water containers under typical Chadian temperatures. Methods Four container types (plastic, glass, gourd, and metal) were seeded with copepods and exposed to simulated Chadian temperatures. Results All copepods in the metal containers died within 4 h. Conversely, after 8 h live copepods were still present in plastic, glass, and gourd containers. Conclusions If provisioned water is provided to potential hosts of D. medinensis, metal containers create the most inhospitable environment for copepods. Plastic containers have little effect on copepod mortality. The use of metal containers for water provisions could be a useful tool assisting with the interruption of D. medinensis transmission among dogs.

A fragment of a Dracunculus-like worm was extracted from the hind limb of a 2-year-old dog from Toledo, Spain. Cytochrome oxidase I and rRNA sequences confirmed an autochthonous mammalian Dracunculus worm infection in Europe. Sequence analyses suggest close relation to a parasite obtained from a North American opossum.

Neglected tropical diseases pose a threat to domestic animal health, as domestic animals can serve as reservoirs for certain zoonotic parasitic infections, including Guinea worm (Dracunculus medinensis) and lymphatic filariasis. Surveillance for these parasites in domestic animals is needed to understand infection prevalence and transmission cycles, with the goal of instituting appropriate interventions. The goal of this research was to report our finding of Brugia sp. infection in dogs from Chad, Africa, and to characterize the genetics and epidemiology of the parasite. During a recent Chadian canine pathogen surveillance project, we identified Brugia sp. infections in a total of 46 out of 428 dogs (10.7%) sampled at three time points in 2019-2020. We found high levels of sequence similarity to B. malayi and B. pahangi based on amplification of 18S rRNA, 5.8S rRNA, and ITS-2 regions. Phylogenetic analysis of 18S rRNA gene sequences placed the Chadian Brugia sp. in a clade with other Brugia spp. but grouped it separately from both B. malayi and B. pahangi. Analysis of Hha I sequences showed the greatest similarity with B. patei, a parasite previously reported from dogs, cats, and wildlife hosts in Kenya. Epidemiologic analysis using generalized linear regression modeling found significantly higher odds of Brugia sp. detection among dogs in villages in southern Chad compared to those in the northern region. Further, within the northern region, there were higher odds of detection in the dry season, compared to the wet season, which is consistent with the ecology of a presumably mosquito-borne parasite. The same 428 dogs were tested for Dirofilaria immitis antigen using a commercial assay (IDEXX SNAP 4Dx) at the earliest time point of the study, with 119 dogs testing positive. However, no association was noted between Brugia infection and a dog being positive for Di. immitis antigen, with only seven of the 119 Di. immitis antigen-positive dogs being Brugia-positive. This is the first report of Brugia sp. in domestic dogs in Chad and additional research is needed to definitively identify the species present, elucidate transmission, and understand potential risks to canine and human health.

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.

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.

Background Guinea worm is a debilitating parasitic infection targeted for eradication. Annual human cases have dropped from approximately 3,500,000 in 1986 to 54 in 2019. Recent identification of canine cases in Chad threatens progress, and therefore detection, prevention, and containment of canine cases is a priority. We investigated associations between disease knowledge, community engagement, and canine cases in Chad to identify opportunities to improve active surveillance. Methods We surveyed 627 respondents (villagers, local leaders, community volunteers, and supervisors) across 45 villages under active surveillance. Descriptive statistics were analyzed by respondent category. Logistic regression models were fitted to assess the effects of volunteer visit frequency on villager knowledge. Results Knowledge increased with respondents’ associations with the Guinea worm program. Household visit frequency by community volunteers was uneven: 53.0% of villagers reported visits at least twice weekly and 21.4% of villagers reported never being visited. Villagers visited by a volunteer at least twice weekly had better knowledge of Guinea worm symptoms (OR: 1.71; 95% CI: 1.04–2.79) and could name more prevention strategies (OR: 2.04; 95% CI: 1.32–3.15) than villagers visited less frequently. The primary motivation to report was to facilitate care-seeking for people with Guinea worm. Knowledge of animal “containment” to prevent contamination of water, knowledge of rewards for reporting animal cases, and ability to name any reasons to report Guinea worm were each positively correlated with village canine case counts. Conclusions Community volunteers play crucial roles in educating their neighbors about Guinea worm and facilitating surveillance. Additional training and more attentive management of volunteers and supervisors could increase visit frequency and further amplify their impact. Emphasizing links between animal and human cases, the importance of animal containment, and animal rewards might improve surveillance and canine case detection. The surveillance system should be evaluated routinely to expand generalizability of data and monitor changes over time., Author summary Guinea worm eradication depends on detecting people and animals with the disease in order to prevent transmission. The situation in Chad is especially urgent because the number of domestic dogs with Guinea worm has been rapidly increasing in the past five years, and now represents the vast majority of Guinea worm cases globally. The global Guinea Worm Eradication Program, the Chad Guinea Worm Eradication Program, and the Chad Ministry of Public Health requested an investigation to evaluate the associations between Guinea worm knowledge, community engagement, and case detection and to investigate how the active surveillance system could be improved to more effectively detect and contain every Guinea worm case. We surveyed 627 people across 45 villages in Chad. We found that Chad’s system for monitoring Guinea worm operates unevenly, with some villagers receiving frequent visits by community volunteers and other villagers reporting never being visited. Villagers visited by a community volunteer at least twice per week had much better knowledge of Guinea worm symptoms and prevention, compared with villagers visited less frequently. Community volunteers are instrumental to Guinea worm eradication efforts in Chad because they transmit key educational messages that facilitate disease detection. More efforts should be made to increase volunteer accountability and to provide volunteers and their supervisors with targeted, high quality training.

Guinea worm (Dracunculus medinensis) has exerted a high human health burden in parts of Africa. Complete eradication of Guinea worm disease (dracunculiasis) may be delayed by the circulation of the parasite in domestic dogs. As with humans, dogs acquire the parasite by directly ingesting infected copepods, and recent evidence suggests that consuming frogs that ingested infected copepods as tadpoles may be a viable transmission route (paratenic route). To understand the relative contributions of direct and paratenic transmission routes, we developed a mathematical model that describes transmission of Guinea worm between dogs, copepods and frogs. We explored how the parasite basic reproductive number (R0) depends on parameters amenable to actionable interventions under three scenarios: frogs/tadpoles do not consume copepods; tadpoles consume copepods but frogs do not contribute to transmission; and frogs are paratenic hosts. We found a non-monotonic relationship between the number of dogs and R0. Generally, frogs can contribute to disease control by removing infected copepods from the waterbody even when paratenic transmission can occur. However, paratenic transmission could play an important role in maintaining the parasite when direct transmission is reduced by interventions focused on reducing copepod ingestion by dogs. Together, these suggest that the most effective intervention strategies may be those which focus on the reduction of copepods, as this reduces outbreak potential irrespective of the importance of the paratenic route.

ObjectivesTo quantify conflict events and access across countries that remain to be certified free of transmission of Dracunculus medinensis (Guinea worm disease) or require postcertification surveillance as part of the Guinea Worm Eradication Programme (GWEP).Setting and participantsPopulations living in Guinea worm affected areas across seven precertification countries and 13 postcertification sub-Saharan African countries.Outcome measuresThe number of conflict events and rates per 100 000 population, the main types of conflict and actors reported to be responsible for events were summarised and mapped across all countries. Chad and Mali were presented as case studies. Guinea worm information was based on GWEP reports. Conflict data were obtained from the Armed Conflict Location and Event Data Project. Maps were created using ArcGIS V.10.7 and access was measured as regional distance and time to cities.ResultsMore than 980 000 conflict events were reported between 2000 and 2020, with a significant increase since 2018. The highest number and rates were reported in precertification Mali (n=2556; 13.0 per 100 000), South Sudan (n=2143; 19.4), Democratic Republic of Congo (n=7016; 8.1) and postcertification Nigeria (n=6903; 3.4), Central Africa Republic (n=1251; 26.4), Burkina Faso (n=2004; 9.7). Violence against civilians, protests and battles were most frequently reported with several different actors involved including Unidentified Armed Groups and Boko Haram. Chad and Mali had contracting epidemiological and conflict situations with affected regions up to 700 km from the capital or 10 hours to the nearest city.ConclusionsUnderstanding the spatial–temporal patterns of conflict events, identifying hotspots, the actors responsible and their sphere of influence is critical for the GWEP and other public health programmes to develop practical risk assessments, deliver essential health interventions, implement innovative surveillance, determine certification and meet the goals of eradication.

Background Guinea worm–Dracunculus medinensis–was historically one of the major parasites of humans and has been known since antiquity. Now, Guinea worm is on the brink of eradication, as efforts to interrupt transmission have reduced the annual burden of disease from millions of infections per year in the 1980s to only 54 human cases reported globally in 2019. Despite the enormous success of eradication efforts to date, one complication has arisen. Over the last few years, hundreds of dogs have been found infected with this previously apparently anthroponotic parasite, almost all in Chad. Moreover, the relative numbers of infections in humans and dogs suggests that dogs are currently the principal reservoir on infection and key to maintaining transmission in that country. Principal findings In an effort to shed light on this peculiar epidemiology of Guinea worm in Chad, we have sequenced and compared the genomes of worms from dog, human and other animal infections. Confirming previous work with other molecular markers, we show that all of these worms are D. medinensis, and that the same population of worms are causing both infections, can confirm the suspected transmission between host species and detect signs of a population bottleneck due to the eradication efforts. The diversity of worms in Chad appears to exclude the possibility that there were no, or very few, worms present in the country during a 10-year absence of reported cases. Conclusions This work reinforces the importance of adequate surveillance of both human and dog populations in the Guinea worm eradication campaign and suggests that control programs aiming to interrupt disease transmission should stay aware of the possible emergence of unusual epidemiology as pathogens approach elimination., Author summary Guinea worm–Dracunculus medinensis–was historically one of the major parasites of humans and has been known since antiquity. Guinea worm is now on the brink of eradication, as a global effort seeking to make this parasite extinct has reduced the number of people infected each year from millions in the 1980s to only 54 human cases in 2019. Despite the enormous success of eradication efforts to date, one complication has arisen. Over the last few years, hundreds of dogs have been found infected with Guinea worm, which was previously considered to be transmitted between people. Almost all of these infected animals are in Chad. We have used whole-genome sequence data to try and understand this peculiar situation. We confirm that the same population of worms are causing both infections and show suspected transmission from humans to dogs. The diversity of worms in Chad appears to exclude the possibility that there were no, or very few, worms present in the country during a 10-year absence of reported cases. This work reinforces the importance of adequate surveillance of both human and dog populations and suggests that control programs should stay aware of the emergence of unusual epidemiology as pathogens approach elimination.

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.

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.

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.L'objectif de cette étude était d'identifier les défis existants sur le dernier kilomètre du programme mondial d'éradication de la dracunculose. MÉTHODE: Revue systématique des articles publiés du 1er janvier 2000 au 31 décembre 2019. Les articles répertoriés dans les bases de données Cochrane Library, Google Scholar, ProQuest PubMed et Web of Science ont été recherchés et examinés. RÉSULTATS: Vingt-cinq articles répondaient aux critères d'inclusion de l'étude et ont été sélectionnés pour l'analyse. Par conséquent, les données pertinentes ont été extraites, regroupées et analysées de manière descriptive. Les résultats ont révélé 10 principaux défis compliquant le dernier kilomètre de l'éradication mondiale du ver de Guinée: mode de transmission inhabituel, infection animale croissante du ver de Guinée, surveillance sous-optimale, insécurité, inaccessibilité; points d'eau salubres inadéquats, migration, mauvaises mesures de confinement des cas, changements écologiques et de nouveaux foyers géographiques de la maladie.Cette revue systématique montre que la plupart des défis actuels de l'éradication du ver de Guinée ont été présents depuis le début de la campagne. Cependant, le changement récent des profils épidémiologiques et de la nature de la dracunculose dans les derniers pays d'endémie restants illustre une nouvelle tournure. Compte tenu de la nature complexe des défis actuels, il semble nécessaire d'adopter une approche plus coordonnée et multidisciplinaire des mesures de prévention et de lutte contre la dracunculose. Ces nouvelles stratégies contribueraient à faire l’histoire en permettant l’éradication de la dracunculose en tant que toute première maladie parasitaire.

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 IgG(4) 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 IgG(4) 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.

Few human infectious diseases have been driven as close to eradication as dracunculiasis, caused by the Guinea worm parasite (Dracunculus medinensis). The number of human cases of Guinea worm decreased from an estimated 3.5 million in 1986 to mere hundreds by the 2010s. In Chad, domestic dogs were diagnosed with Guinea worm for the first time in 2012, and the numbers of infected dogs have increased annually. The presence of the parasite in a non-human host now challenges efforts to eradicate D. medinensis, making it critical to understand the factors that correlate with infection in dogs. In this study, we evaluated anthropogenic and environmental factors most predictive of detection of D. medinensis infection in domestic dog populations in Chad. Using boosted regression tree models to identify covariates of importance for predicting D. medinensis infection at the village and spatial hotspot levels, while controlling for surveillance intensity, we found that the presence of infection in a village was predicted by a combination of demographic (e.g. fishing village identity, dog population size), geographic (e.g. local variation in elevation), and climatic (e.g. precipitation and temperature) factors, which differed between northern and southern villages. In contrast, the presence of a village in a spatial infection hotspot, was primarily predicted by geography and climate. Our findings suggest that factors intrinsic to individual villages are highly predictive of the detection of Guinea worm parasite presence, whereas village membership in a spatial infection hotspot is largely determined by location and climate. This study provides new insight into the landscape-scale epidemiology of a debilitating parasite and can be used to more effectively target ongoing research and possibly eradication and control efforts., Author summary The eradication of human infectious diseases has proven remarkably difficult. The world has only succeeded once, in the case of the smallpox virus. However, international efforts have driven the debilitating Guinea worm parasite closer to the brink of eradication than nearly any other parasite. Coordinated efforts by the Ministries of Health in endemic countries, the U.S. Centers for Disease Control, The Carter Center, and the World Health Organization have reduced the number of annual Guinea worm cases from millions in the 1980s to hundreds in the early 2010s, but recently a new threat has emerged. Guinea worm infections have been diagnosed in domestic dogs, particularly in the Republic of Chad, and numbers of infections have continued to increase. As in many countries where dracunculiasis is endemic, the campaign for eradication in Chad has focused intervention measures on interrupting transmission among humans, so infection in dogs jeopardizes eradication efforts. In this study, we used machine learning methods to identify demographic, geographic, and climatic factors associated with the presence of Guinea worm-infected dogs at the village level, and spatial clustering of dog cases regionally. A combination of demographic, geographic and climatic factors were important correlates of infection at the village level, but the importance of these factors varied between northern and southern populations of the parasite. At the larger village cluster level, the geographic position and climate of a village were most important. Some of our findings, including the importance of fishing villages and the difference in correlates between northern and southern villages can be used by researchers to guide additional data collection and by public health workers to better target eradication efforts. More generally, this work contributes to a broader understanding of the spatial patterning of multi-host infectious diseases of humans and animals.

Guinea worm Dracunculus medinensis causes debilitating disease in people and is subject to an ongoing global eradication programme. Research and controls are constrained by a lack of diagnostic tools. We developed a specific and sensitive LAMP method for detecting D. medinensis larval DNA in copepod vectors. We were able to detect a single larva in a background of field-collected copepods. This method could form the basis of a “pond-side test” for detecting potential sources of Guinea worm infection in the environment, in copepods, including in the guts of fish as potential transport hosts, enabling research, surveillance and targeting of control measures. The key constraint on the utility of this assay as a field diagnostic, is a lack of knowledge of variation in the temporal and spatial distribution of D. medinensis larvae in copepods in water bodies in the affected areas and how best to sample copepods to obtain a reliable diagnostic sample. These fundamental knowledge gaps could readily be addressed with field collections of samples across areas experiencing a range of worm infection frequencies, coupled with field and laboratory analyses using LAMP and PCR., Highlights • LAMP tests were developed for Dracunculus medinensis and D. insignis and were shown to be specific and sensitive. • A LAMP test was developed to amplify DNA from copepods to use as an internal amplification control during testing. • Samples of copepods taken from ponds could be tested using the LAMP tests and Dracunculus medinensis could be detected. • Results are achieved in less than 30 min using just the Genie III instrument and no other laboratory equipment is necessary.

Global eradication of human Guinea worm disease (dracunculiasis) has been set back by the emergence of infections in animals, particularly domestic dogs Canis familiaris. The ecology and epidemiology of this reservoir is unknown. We tracked dogs using GPS, inferred diets using stable isotope analysis and analysed correlates of infection in Chad, where numbers of Guinea worm infections are greatest. Dogs had small ranges that varied markedly among villages. Diets consisted largely of human staples and human faeces. A minority of ponds, mostly, Author summary Guinea worm is a parasite that causes profoundly debilitating disease in humans. An eradication program has been successful in nearly eliminating the disease from people. However, the same worm has now been found in domestic dogs and the frequency of detecting Guinea worm in dogs has been increasing. This means that to eradicate Guinea worm, the infection must be eliminated in dogs as well as in people. However, not much is known about the disease in dogs. This study is the first to investigate dog ecology in relation to Guinea worm infection. We worked in the worst-affected country, Chad. We attached GPS collars to dogs to track their ranging and use of water bodies and analysed their diets using a forensic technique, based on analysing stable isotope compostion of their whiskers and potential food items. We showed that dogs living in households that provided water to their animals had a lower risk of having had Guinea worm and that dogs that ate more fish had an increased risk. These findings suggest there is a classical route for worm transmission in dogs, via drinking contaminated water, as well as a novel route, potentially by eating fish carrying a source of infection.

Exploitation of natural resources is a driver of human infectious disease emergence. The emergence of animal reservoirs of Guinea worm Dracunculus medinensis, particularly in domestic dogs Canis familiaris, has become the major impediment to global eradication of this human disease. 93% of all Guinea worms detected worldwide in 2020 were in dogs in Chad. Novel, non-classical pathways for transmission of Guinea worm in dogs, involving consumption of fish, have been hypothesized to support the maintenance of this animal reservoir. We quantified and analyzed variation in Guinea worm emergence in dogs in Chad, across three climatic seasons, in multiple villages and districts. We applied forensic stable isotope analyses to quantify dietary variation within and among dogs and GPS tracking to characterize their spatial ecology. At the end of the hot-dry season and beginning of the wet season, when fishing by people is most intensive, Guinea worm emergence rates in dogs were highest, dogs ate most fish, and fish consumption was most closely associated with disease. Consumption of fish by dogs enables a non-classical transmission pathway for Guinea worm in Chad. Seasonal fisheries and the facilitation of dogs eating fish are likely contributing to disease persistence and to this key impediment to human disease eradication. Interrelated natural resource use, climatic variation, companion animal ecology, and human health highlight the indispensability of One Health approaches to the challenges of eradicating Guinea worm and other zoonotic diseases.

Plant parasitic cyst nematodes induce specific hypermetabolic syncytial nurse cell structures in host roots. A characteristic feature of syncytia is the lack of the central vacuole and the formation of numerous small and larger vesicles. We show that these structures are formed de novo via widening of ER cisternae during the entire development of syncytium, whereas in advanced stages of syncytium development, larger vacuoles are also formed via fusion of vesicles/tubules surrounding organelle-free pre-vacuole regions. Immunogold transmission electron microscopy of syncytia localised the vacuolar markers E subunit of vacuolar H+-adenosinetriphosphatase (V-ATPase) complex and tonoplast intrinsic protein (γ-TIP1;1) mostly in membranes surrounding syncytial vesicles, thus indicating that these structures are vacuoles and that some of them have a lytic character. To study the function of syncytial vacuoles, changes in expression of AtVHA-B1, AtVHA-B2 and AtVHA-B3 (coding for isoforms of subunit B of V-ATPase), and TIP1;1 and TIP1;2 (coding for γ-TIP proteins) genes were analysed. RT-qPCR revealed significant downregulation of AtVHA-B2, TIP1;1 and TIP1;2 at the examined stages of syncytium development compared to uninfected roots. Expression of VHA-B1 and VHA-B3 decreased at 3 dpi but reached the level of control at 7 dpi. These results were confirmed for TIP1;1 by monitoring At-γ-TIP-YFP reporter construct expression. Infection test conducted on tip1;1 mutant plants showed formation of larger syncytia and higher numbers of females in comparison to wild-type plants indicating that reduced levels or lack of TIP1;1 protein promote nematode development. Electronic supplementary material The online version of this article (10.1007/s00709-018-1303-4) contains supplementary material, which is available to authorized users.

This report summarizes the status of the global Dracunculiasis Eradication Program as of the end of 2017. Dracunculiasis (guinea worm disease) has been eliminated from 19 of 21 countries where it was endemic in 1986, when an estimated 3.5 million cases occurred worldwide. Only Chad and Ethiopia reported cases in humans, 15 each, in 2017. Infections of animals, mostly domestic dogs, with Dracunculus medinensis were reported in those two countries and also in Mali. Insecurity and infections in animals are the two main obstacles remaining to interrupting dracunculiasis transmission completely.

We reviewed 62 new cases and 18 published reports of Dracunculus infections in domestic dogs and cats to describe the epidemiology of this parasite in dogs and cats in North America. We collected host and parasite data when available, including age, sex, and breed of dog, nematode location in the host, and any clinical signs at presentation and/or description of the apparent lesion. For dogs, infections were noted in six of the AKC breed groups, but none was reported from the toy group or the miscellaneous breed class. Age of infected dogs ranged from 7 months to 19 years (median 4 years; average 5.3 years), and infection rates were similar in male and female dogs. Most nematodes were associated with the distal extremities, but worms were also found in the chest/thorax, abdomen, head, and flank. Although most infected dogs had a single worm, three dogs had two or more worms that were collected from multiple lesions. Three new cat cases, with similar lesions, presentations and seasonality, were detected in Alabama, North Carolina and Texas. Cases were reported from a wide geographic range throughout eastern North America, during every month of the year, but 72% of infections were diagnosed in the late winter to early spring (December to May). All collected worms were larvigerous females which cannot be identified to species based on morphologic characters. Thus, we attempted to amplify and sequence a portion of the cytochrome c oxidase subunit I (COI) gene for specific identification. Although 13 worms from 12 cases were available, sequences were obtained for only eight worms from seven cases. These eight worms were D. insignis, a common parasite of raccoons (Procyon lotor) and other primarily carnivorous mammals. Female worms are the most likely to be detected in dogs and cats because male worms do not emerge, parasites should be preserved in ethanol for molecular identification. Although this study used convenience sampling of available data, we found that the parasite is widespread throughout the eastern US and Canada and that Dracunculus infections in dogs are more common than is revealed in published literature. However, more research is needed to understand the epidemiology, including transmission route(s), prevalence, and distribution of this parasite.

Despite several periods of stagnating guinea worm disease (GWD) incidence in Ghana during its national eradication campaign in the 1990s and early 2000s, the last reported case of GWD was in May 2010. In July 2011, Ghana celebrated the interruption of guinea worm (GW) transmission. Although it has been established that GWD causes disability, pain, and socioeconomic hardship, there is a dearth of population-based evidence collected in post-GW–endemic countries to document the value attributed to GWD eradication by residents in formerly endemic communities. Given Ghana’s recent history of GWD and a concentrated burden of the disease in its Northern Region, a pattern which remained true through to the final stage of the eradication campaign, seven villages in the Northern Region were targeted for a retrospective, cross-sectional study to detail the perceptions, attitudes, and beliefs about the impact of eradication of GWD in northern Ghana. The study revealed that respondents from the sampled communities felt GW eradication improved their socioeconomic conditions, as the impact of infection prohibited the pursuit of individual and social advancement. The value residents placed on the absence of GWD highlights both the impact infection had on the pursuit of social and economic advancement and the newfound ability to be disease-free and productive. Of the 143 respondents, 133 had GWD in the past and were incapacitated for an average of 6 weeks annually per GW infection, with each infected person affected nearly four times in his or her lifetime.

Background 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. Methods 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. Results 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. Conclusions 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., Author summary Guinea worm disease has no pharmacological treatment or vaccines, and therefore existing prevention and control strategies (e.g., case containment, health education, chemical treatment of water bodies) are critically dependent on timely, accurate, and actionable data. We conducted informant interviews, used conceptual frameworks, and mapped data flow to evaluate the Chad Guinea Worm Eradication Program’s current information system. We identified areas for improvement including the need to consolidate variables across data collection forms and the need to develop streamlined workflows. We proposed a four-phased roadmap for transitioning to an electronic data capture system and centralizing data storage. Our approach and proposed roadmap could be adopted by other neglected tropical disease control programs looking to modernize data collection and storage procedures.

Guinea-worm disease (GWD) was thought to be almost eliminated in Chad when it reemerged in 2010. The disease now shows a peculiar pattern of spreading along Chari River and its tributaries, rather than clustering around a particular drinking water source. We create a mathematical model of GWD that includes the population dynamics of the parasite as well as the dynamics of its hosts (copepods, fish, humans, and domestic dogs). We calibrate our model based on data from the literature and validate it on the recent GWD annual incidence data from Chad. The effective reproduction number predicted by our model agrees well with the empirical value of roughly 1.25 derived directly from the data. Our model thus supports the hypothesis that the parasite now uses fish as intermediate transport hosts. We predict that GWD transmission can be most easily interrupted by avoiding eating uncooked fish and by burying the fish entrails to prevent transmission through dogs. Increasing the mortality of copepods and even partially containing infected dogs to limit their access to water sources is another important factor for GWD eradication.

Summary Global eradication of the guinea worm (Dracunculus medinensis) is near, although perhaps delayed a little by the discovery of a transmission cycle in dogs. It is therefore an appropriate time to reflect on the severe impact of this infection on the life of the communities where it was endemic prior to the start of the global eradication programme in 1981. From 1971 to 1974, we conducted a series of unpublished studies on guinea worm in a group of villages in Katsina State, northern Nigeria, where the infection was highly endemic. These studies demonstrated the high rate of infection in affected communities, the frequent recurrence of the infection in some subjects and the long‐standing disability that remained in some infected individuals. Immunological studies showed a high level of immediate hypersensitivity to adult worm and larval antigens but a downregulation of Th1‐type T‐cell responses to worm antigens. Freeing communities such as those described in this article from the scourge of guinea worm infection for good will be an important public health triumph.

Dracunculus medinensis, the causative agent of Guinea worm disease in humans, is being reported with increasing frequency in dogs. However, the route(s) of transmission to dogs is still poorly understood. Classical transmission to humans occurs via drinking water that contains cyclopoid copepods infected with third stage larvae of D. medinensis, but due to the method of dog drinking (lapping) compared to humans (suction and/or retrieval of water into containers), it seems unlikely that dogs would ingest copepods readily through drinking. We exposed lab raised beagles to varying densities of uninfected copepods in 2 liters of water to evaluate the number of copepods ingested during a drinking event. We confirmed dogs can ingest copepod intermediate hosts while drinking; however, low numbers were ingested at the densities that are typically observed in Chad suggesting this transmission route may be unlikely. Overall, the relative importance of the classic transmission route and alternate transmission routes, such as paratenic and transport hosts, needs investigation in order to further clarify the epidemiology of guinea worm infections in dogs.