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Lancet (London, England) Dec 2020
Topics: Africa; Animals; COVID-19; Disease Eradication; Disease Reservoirs; Dogs; Dracunculiasis; Dracunculus Nematode; Drinking Water; Endemic Diseases; Health Knowledge, Attitudes, Practice; Health Policy; Health Promotion; Humans; Incidence; SARS-CoV-2
PubMed: 33278938
DOI: 10.1016/S0140-6736(20)32553-8 -
PLoS Neglected Tropical Diseases Nov 2020Guinea 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...
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.
Topics: Africa; Animals; Disease Reservoirs; Dog Diseases; Dogs; Dracunculiasis; Dracunculus Nematode; Female; Genome, Helminth; Humans; Male; Mammals
PubMed: 33253172
DOI: 10.1371/journal.pntd.0008623 -
The Veterinary Record Nov 2020discusses new research investigating the role of domestic dogs in sustaining Guinea worm disease in Africa.
discusses new research investigating the role of domestic dogs in sustaining Guinea worm disease in Africa.
Topics: Animals; Disease Eradication; Dog Diseases; Dogs; Dracunculiasis; Humans
PubMed: 33188099
DOI: 10.1136/vr.m4401 -
The American Journal of Tropical... Jan 2021Increased 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....
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--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 ( = 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.
Topics: Animals; Antibodies, Helminth; Antibodies, Monoclonal; Chad; Dog Diseases; Dogs; Dracunculiasis; Dracunculus Nematode; Enzyme-Linked Immunosorbent Assay; Immunoglobulin G; Reproducibility of Results; Serologic Tests
PubMed: 33124546
DOI: 10.4269/ajtmh.20-0914 -
MMWR. Morbidity and Mortality Weekly... Oct 2020Dracunculiasis (Guinea worm disease) is caused by the parasite Dracunculus medinensis and is acquired by drinking water containing copepods (water fleas) infected with...
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.
Topics: Animals; Disease Eradication; Dog Diseases; Dogs; Dracunculiasis; Global Health; Humans
PubMed: 33119555
DOI: 10.15585/mmwr.mm6943a2 -
The Journal of Parasitology Oct 2020The prevalence and diversity of parasitic nematodes in wildlife have been well studied for certain species, yet for others considerable gaps in knowledge exist. The...
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.
Topics: Amphibians; Animals; Animals, Wild; Armadillos; Chad; Coyotes; Dracunculiasis; Dracunculus Nematode; Female; Fishes; Genetic Variation; Georgia; Life Cycle Stages; Male; Mammals; Opossums; Phylogeny; Ponds; Prevalence; Raccoons
PubMed: 33009554
DOI: 10.1645/18-178 -
Food and Waterborne Parasitology Sep 2020Waterborne parasitic diseases form one of common and important public health and economic problems in low- and middle-income countries, though little is known on the...
Waterborne parasitic diseases form one of common and important public health and economic problems in low- and middle-income countries, though little is known on the burden and patterns of these diseases in most regions. This systematic scoping review informs on the prevalence and pattern of waterborne parasitic infections in eastern Africa from 1st of January 1941 to 31st of December 2019. The review found limited number of published studies on waterborne parasitic diseases, though 13 of the 15 studied countries in eastern Africa provided one or more published report(s) totalling 47 reports. Focus of studies was mainly on schistosomiasis where 44.8% of the 47 retrieved studies reported it. Other frequently reported diseases were giardiasis (23.4% of reports), soil-transmitted helminths (23.4%) and amoebiasis (21.3%). Rarely reported diseases were malaria, cryptosporidiosis, isosporiasis, dracunculiasis and trichomoniasis. Based on parasitological examinations, schistosomiasis prevalence ranged from 17 to 33% in Burundi, 1.9 to 73.9% in Ethiopia, 2.1 to 18% in Kenya, 7.2 to 88.6% in Uganda, 22.9 to 86.3% in Tanzania, 27.2 to 65.8% in Somalia, 15 to >50% in Mauritius, 2.4% in Eritrea and 5.0 to 93.7% in Madagascar. Amoebiasis prevalence was 4.6-15,3% (Ethiopia), 5.9-58.3% (Kenya), 54.5% (Rwanda), 0.7-2.7% (Sudan), 19.93% (Uganda) and 4.5-5.0% (Seychelles). Giardiasis prevalence was 0.6-55.0% (Ethiopia), 16.6% (Kenya), 3.6% (Rwanda), 21.1% (Sudan), 40.7% (Uganda), 45.0% (Eritrea) and 3.3-6.0% (Seychelles). Soil-transmitted helminths prevalence was 41.7-52.4% (Ethiopia), 32.4-40.7% (Kenya), 9997 cases (Rwanda), 85.0% (Somalia), 4.7% (Madagascar) and 1.1-84% (Seychelles), , and hookworms were the most common helminths detected. Malaria prevalence was 2.9-4.31% (Ethiopia), an annual episode of 9 million people (Sudan), 13.0% (Tanzania), 146 hospital cases (Madagascar), 1.4-2.0% (Seychelles) and <5.0% in Djibouti. It is also observed that >50% of the populations in eastern Africa region lack improved drinking water sources or sanitation facilities. This may account for the observed high prevalence of the diseases. The author also suggests likely underestimation of the prevalence as most waterborne parasitic diseases are neglected and cases likely only recorded and left unpublished in health facilities. Thus for a thorough mapping of burdens of these diseases, grey literature, including hospital records must be reviewed while interventions focusing on improved water and sanitation are likely to reduce the burden considerably.
PubMed: 32995583
DOI: 10.1016/j.fawpar.2020.e00089 -
Tropical Medicine & International... Dec 2020The objective of this study was to identify the existing 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.
Topics: Animals; Communicable Disease Control; Disease Eradication; Dracunculiasis; Dracunculus Nematode; Humans; Water Supply
PubMed: 32946140
DOI: 10.1111/tmi.13492 -
PLoS Neglected Tropical Diseases Sep 2020Few human infectious diseases have been driven as close to eradication as dracunculiasis, caused by the Guinea worm parasite (Dracunculus medinensis). The number of...
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.
Topics: Animals; Chad; Climate; Disease Eradication; Dog Diseases; Dogs; Dracunculiasis; Dracunculus Nematode; Geography; Machine Learning
PubMed: 32925916
DOI: 10.1371/journal.pntd.0008620 -
The American Journal of Tropical... Nov 2020The campaign to eradicate dracunculiasis (Guinea worm [GW] disease) and its causative pathogen (GW) in Chad is challenged by infections in domestic dogs, which far...
The campaign to eradicate dracunculiasis (Guinea worm [GW] disease) and its causative pathogen (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, , 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.
Topics: Animals; Chad; Computer Simulation; Dog Diseases; Dogs; Dracunculiasis; Dracunculus Nematode; Environment; Female; Life Cycle Stages; Models, Theoretical; Seasons; Temperature; Water
PubMed: 32901603
DOI: 10.4269/ajtmh.19-0466