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

OBJECTIVE: The objective of this study was to identify the existing challenges in the last mile of the global Guinea Worm Eradication Program. METHODS: 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. RESULTS: 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. CONCLUSION: 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.

OBJECTIF: 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. CONCLUSION: 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.

Dracunculiasis: water-borne anthroponosis vs. food-borne zoonosis.

Dracunculiasis is the first parasitic disease set for eradication. However, recent events related to the Dracunculus medinensis epidemiology in certain African countries are apparently posing new challenges to its eradication. Two novel facts have emerged: the existence of animal reservoirs (mainly dogs but also cats and baboons), and possibly a new food-borne route of transmission by the ingestion of paratenic (frogs) or transport (fish) hosts. Therefore, instead of being exclusively a water-borne anthroponosis, dracunculiasis would also be a food-borne zoonosis. The existence of a large number of infected dogs, mainly in Chad, and the low number of infected humans, have given rise to this potential food-borne transmission. This novel route would concern not only reservoirs, but also humans. However, only animals seem to be affected. Dracunculus medinensis is on the verge of eradication due to the control measures which, classically, have been exclusively aimed at the water-borne route. Therefore, food-borne transmission is probably of secondary importance, at least in humans. In Chad, reservoirs would become infected through the water-borne route, mainly in the dry season when rivers recede, and smaller accessible ponds, with a lower water level containing the infected copepods, appear, whilst humans drink filtered water and, thus, avoid infection. The total absence of control measures aimed at dogs (or at other potential reservoirs) up until the last years, added to the stimulating reward in cash given to those who find parasitized dogs, have presumably given rise to the current dracunculiasis scenario in Chad.

Possible Role of Fish as Transport Hosts for Dracunculus spp. Larvae.

To inform Dracunculus medinensis (Guinea worm) eradication efforts, we evaluated the role of fish as transport hosts for Dracunculus worms. Ferrets fed fish that had ingested infected copepods became infected, highlighting the importance of recommendations to cook fish, bury entrails, and prevent dogs from consuming raw fish and entrails.

Guinea worm infection in northern Nigeria: reflections on a disease approaching eradication.

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.

Guinea worm: from Robert Leiper to eradication.

Guinea worm disease, dracunculiasis or dracontiasis, is an ancient disease with records going back over 4500 years, but until the beginning of the 20th century, little was known about its life cycle, particularly how humans became infected. In 1905, Robert Thomas Leiper was sent by the British colonial authorities to West Africa to investigate the spread of Guinea worm disease and to recommend measures to prevent it. While carrying out his investigations, he made important contributions to the aetiology, epidemiology and public health aspects of Guinea worm disease and provided definitive answers to many outstanding questions. First, he tested the validity of previous theories; second, he confirmed the role of water fleas, which he identified as Cyclops, as the intermediate hosts in the life cycle; third, he investigated the development of the parasite in its intermediate host; and fourth, he recommended measures to prevent the disease. [The crustacean Order Cyclopoida in the Family Cyclopidae contains 25 genera, including Cyclops which itself contains over 400 species and may not even be a valid taxon. It is not known how many of these species (or indeed species belonging to related genera) can act as intermediate hosts of Dracunculus medinensis nor do we know which species Fedchenko, Leiper and other workers used in their experiments. It is, therefore, best to use the terms copepod, or copopoid crustacean rather than Cyclops in scientific texts. In this paper, these crustaceans are referred to as copepods except when referring to an original text.] Leiper described the remarkable changes that took place when an infected copepod was placed in a dilute solution of hydrochloric acid; the copepod was immediately killed, but the Dracunculus larvae survived and were released into the surrounding water. From this, he concluded that if a person swallowed an infected copepod, their gastric juice would produce similar results. He next infected monkeys by feeding them copepods infected with Guinea worm larvae, and thus conclusively demonstrated that humans became infected by accidentally ingesting infected crustaceans. Based on these conclusions, he advocated a number of control policies, including avoidance of contaminated drinking water or filtering it, and these preventive measures paved the way for further research. The challenge to eradicate Guinea worm disease was not taken up until about seven decades later since when, with the support of a number of governmental and non-governmental organizations, the number of cases has been reduced from an estimated 3·5 million in 1986 to 25 in 2016 with the expectation that this will eventually lead to the eradication of the disease.

Elimination of Guinea Worm Disease in Ethiopia; Current Status of the Disease's, Eradication Strategies and Challenges to the End Game.

Dracunculiasis, also named Guinea Worm Disease (GWD), is one of the Neglected Tropical Diseases (NTDs) caused by a parasitic nematode known as Dracunculus medinensis and has been known since antiquity as 'fiery serpent' from Israelites. It is transmitted to humans via drinking contaminated water containing infective copepods. Given, its feasibility for eradication, the Guinea Worm Eradication Program (GWEP) was launched in 1980 with the aim of eradicating the disease. Since its inception, GWEP has made an extraordinary progress in interrupting transmission. Globally, the number of reported cases reduced from 3.5 million in 20 countries in 1986 to only 22 cases in 2015 from only four countries namely South Sudan, Mali, Chad and Ethiopia. Since Mali has interrupted transmission of GWD in 2016, currently, the disease remains endemic in only three sub-Saharan African countries namely, South Sudan, Chad and Ethiopia. Each endemic country has its own national Guinea Worm Eradication Program. In Ethiopia, the Ethiopian Dracunculiasis Eradication Program (EDEP) which was established in 1993 has made remarkable move towards interruption of disease transmission and now the endgame is fast approaching. The EDEP with support mainly from The Carter Center, WHO, and UNICEF has reduced GWD by more than 99% from 1994 to 2015. In 2015, only 3 indigenous cases in humans and 14 in animals (13 in dogs and 1 in baboon) were reported. In 2016, 3 human cases, 14 dogs and 2 baboon infections were reported.. Refugee influx from the Republic of South Sudan (RSS), increased animal infections with unknown role in transmission of Dracunculiasis, the presence of hard to reach communities and lack of safe water sources in remote non-village areas remain among important challenges at this final stage of GWD eradication in Ethiopia. This paper reviews progress made towards Guinea Worm Eradication with a focus on the experience of the Ethiopian Dracunculiasis Eradication Program (EDEP), and intervention strategies that need further intensification to realize the endgame. Eradication strategies encompassing community education for behavioral change including raising awareness towards cash reward for reporting Guniea Worm Disease (GWD) and animal infection, case containment, surveillance systems, provision of safe water supply, and ABATE chemical application are discussed. It also summarizes challenges the end game faces and recommendations to strengthen the eradication effort.

Progress toward global eradication of dracunculiasis--January 2011-June 2012.

Dracunculiasis (Guinea worm disease) is caused by Dracunculus medinensis, a parasitic worm. Approximately 1 year after initial infection from contaminated drinking water, the worm emerges through the skin of the infected person, usually on the lower limb. Pain and secondary bacterial wound infection can cause temporary or permanent disability that disrupts work and schooling for the entire family. In 1986, the World Health Assembly (WHA) called for dracunculiasis elimination and the Guinea Worm Eradication Program, supported by The Carter Center, World Health Organization (WHO), United Nations Children's Fund (UNICEF), CDC, and other partners, was coalesced to assist ministries of health of endemic countries in meeting this goal. At that time, an estimated 3.5 million cases occurred annually in 20 countries in Africa and Asia. This report updates published and previously unpublished surveillance data reported by ministries of health and describes progress toward global dracunculiasis eradication. In 2011, a total of 1,058 cases were reported. As of 2012, dracunculiasis remained endemic in only four countries. Through June 2012, worldwide reductions in reported cases continued, compared with the first 6 months of 2011. Failures in surveillance and containment, lack of clean drinking water, and insecurity in Mali and parts of South Sudan continue to challenge dracunculiasis eradication efforts.

Infectious disease: Dog diets may drive transmission cycles in human Guinea worm disease.

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.

Renewed transmission of dracunculiasis--Chad, 2010.

Transmission of dracunculiasis (Guinea worm disease), a waterborne, parasitic disease targeted for eradication, was thought to have been interrupted in Chad since 2000, when the last case was reported. However, in 2010, 10 cases were confirmed by the Chad Ministry of Public Health (Ministère de la Santé Publique [MSP]) and the World Health Organization (WHO) during field investigations in which rumored cases were investigated and nearby villages were actively searched for additional cases. Because patients were not prevented from contaminating water sources, new cases were expected in 2011. During January-February 2011, MSP, WHO, and CDC conducted an investigation to gather additional information to guide prevention and response activities before the 2011 transmission season. Seven districts where cases had been confirmed or suspected in 2010 or where dracunculiasis was endemic during 1994-2000 were surveyed. The results of those surveys indicated that residents of 116 (55%) of 210 villages and 13 (87%) of 15 nomad camps consumed water from unsafe sources; 157 (75%) of 209 village key informants (KIs) and five (33%) of 15 nomad camp KIs knew about dracunculiasis. Thirty-one villages had confirmed or suspected cases during 2009-2011 and were classified as at-risk, requiring weekly active surveillance and urgent pre-positioning of materials for the 2011 transmission season. Nomadic populations are at risk for dracunculiasis because of unsafe water consumption and minimal knowledge of the disease. These populations also require targeted surveillance and prevention efforts (e.g., filter distribution, education, and case containment) to interrupt dracunculiasis transmission .

Ecology of domestic dogs (Canis familiaris) as a host for Guinea worm (Dracunculus medinensis) infection in Ethiopia.

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.

Progress toward global eradication of dracunculiasis, January 2009-June 2010.

In 1986, the World Health Assembly (WHA) called for the elimination of dracunculiasis (Guinea worm disease), a parasitic infection in humans caused by Dracunculus medinensis. At the time, an estimated 3.5 million cases were occurring annually in 20 countries in Africa and Asia, and 120 million persons were at risk for the disease. Because of slow mobilization in countries with endemic disease, the 1991 WHA goal to eradicate dracunculiasis globally by 1995 was not achieved. In 2004, WHA established a new target date of 2009 for global eradication; despite considerable progress, that target date also was not met. This report updates both published and previously unpublished data and updates progress toward global eradication of dracunculiasis since January 2009. At the end of December 2009, dracunculiasis remained endemic in four countries (Ethiopia, Ghana, Mali, and Sudan). The number of indigenous cases of dracunculiasis worldwide had decreased 31%, from 4,613 in 2008 to 3,185 in 2009. Of the 766 cases that occurred during January--June 2010, a total of 745 (97%) were reported from 380 villages in Sudan. Ghana, Ethiopia, and Mali each are close to interrupting transmission, as indicated by the small and declining number of cases. The current target is to complete eradication in all four countries as quickly as possible. Insecurity (e.g., sporadic violence or civil unrest) in areas of Sudan and Mali where dracunculiasis is endemic poses the greatest threat to the success of the global dracunculiasis eradication program.

Setback for campaign to eradicate Guinea worm disease.

Arabella Gray discusses new research investigating the role of domestic dogs in sustaining Guinea worm disease in Africa.

Cooking copepods: The survival of cyclopoid copepods (Crustacea: Copepoda) in simulated provisioned water containers and implications for the Guinea Worm Eradication Program in Chad, Africa.

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.

Identifying correlates of Guinea worm (Dracunculus medinensis) infection in domestic dog populations.

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.

Dogs and the classic route of Guinea Worm transmission: an evaluation of copepod ingestion.

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.