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PLoS Neglected Tropical Diseases Jul 2021Guinea worm (Dracunculus medinensis) was detected in Chad in 2010 after a supposed ten-year absence, posing a challenge to the global eradication effort. Initiation of a...
BACKGROUND
Guinea worm (Dracunculus medinensis) was detected in Chad in 2010 after a supposed ten-year absence, posing a challenge to the global eradication effort. Initiation of a village-based surveillance system in 2012 revealed a substantial number of dogs infected with Guinea worm, raising questions about paratenic hosts and cross-species transmission.
METHODOLOGY/PRINCIPAL FINDINGS
We coupled genomic and surveillance case data from 2012-2018 to investigate the modes of transmission between dog and human hosts and the geographic connectivity of worms. Eighty-six variants across four genes in the mitochondrial genome identified 41 genetically distinct worm genotypes. Spatiotemporal modeling revealed worms with the same genotype ('genetically identical') were within a median range of 18.6 kilometers of each other, but largely within approximately 50 kilometers. Genetically identical worms varied in their degree of spatial clustering, suggesting there may be different factors that favor or constrain transmission. Each worm was surrounded by five to ten genetically distinct worms within a 50 kilometer radius. As expected, we observed a change in the genetic similarity distribution between pairs of worms using variants across the complete mitochondrial genome in an independent population.
CONCLUSIONS/SIGNIFICANCE
In the largest study linking genetic and surveillance data to date of Guinea worm cases in Chad, we show genetic identity and modeling can facilitate the understanding of local transmission. The co-occurrence of genetically non-identical worms in quantitatively identified transmission ranges highlights the necessity for genomic tools to link cases. The improved discrimination between pairs of worms from variants identified across the complete mitochondrial genome suggests that expanding the number of genomic markers could link cases at a finer scale. These results suggest that scaling up genomic surveillance for Guinea worm may provide additional value for programmatic decision-making critical for monitoring cases and intervention efficacy to achieve elimination.
Topics: Animals; Chad; DNA, Helminth; Dracunculiasis; Dracunculus Nematode; Genetic Markers; Genome, Helminth; Genome, Mitochondrial; Humans; Population Surveillance
PubMed: 34310598
DOI: 10.1371/journal.pntd.0009609 -
MMWR. Morbidity and Mortality Weekly... Oct 2016Dracunculiasis (Guinea worm disease) is caused by Dracunculus medinensis, a parasitic worm. Approximately 1 year after a person acquires infection from drinking...
Dracunculiasis (Guinea worm disease) is caused by Dracunculus medinensis, a parasitic worm. Approximately 1 year after a person acquires infection from drinking contaminated water, the worm emerges through the skin, usually on the leg. Pain and secondary bacterial infection can cause temporary or permanent disability that disrupts work and schooling. The campaign to eradicate dracunculiasis worldwide began in 1980 at CDC. In 1986, the World Health Assembly called for dracunculiasis elimination (1), and the global Guinea Worm Eradication Program, led by the Carter Center and supported by the World Health Organization (WHO), United Nations Children's Fund (UNICEF), CDC, and other partners, began assisting ministries of health in countries where dracunculiasis was endemic. In 1986, an estimated 3.5 million cases were occurring each year in 20 countries in Africa and Asia (1,2). Since then, although the goal of eradicating dracunculiasis has not been achieved, substantial progress has been made. Compared with the 1986 estimate, the annual number of reported cases in 2015 has been reduced by >99%, and cases are confined to four countries with endemic disease. This report updates published (3-5) and unpublished surveillance data reported by ministries of health and describes progress toward dracunculiasis eradication during January 2015-June 2016. In 2015, a total of 22 cases were reported from four countries (Chad [nine cases], Mali [five], South Sudan [five], and Ethiopia [three]), compared with 126 cases reported in 2014 from the same four countries (Table 1). The overall 83% reduction in cases from 2014 to 2015 is the largest such annual overall reduction ever achieved during this global campaign. During the first 6 months of 2016, however, cases increased 25% compared with the same period in 2015. Continued active surveillance and aggressive detection and appropriate management of cases are essential eradication program components; however, epidemiologic challenges and civil unrest and insecurity pose potential barriers to eradication.
Topics: Disease Eradication; Dracunculiasis; Global Health; Humans
PubMed: 27736840
DOI: 10.15585/mmwr.mm6540a5 -
Emerging Infectious Diseases Sep 2017To inform Dracunculus medinensis (Guinea worm) eradication efforts, we evaluated the role of fish as transport hosts for Dracunculus worms. Ferrets fed fish that had...
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.
Topics: Animals; Chad; Copepoda; Dog Diseases; Dogs; Dracunculiasis; Dracunculus Nematode; Ferrets; Fish Diseases; Fishes; Food Chain; Host Specificity; Humans; Larva
PubMed: 28820381
DOI: 10.3201/eid2309.161931 -
Scientific Reports Jan 2020Dracunculus medinensis, the causative agent of Guinea worm disease in humans, is being reported with increasing frequency in dogs. However, the route(s) of transmission...
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.
Topics: Animals; Chad; Communicable Disease Control; Copepoda; Disease Vectors; Dogs; Dracunculiasis; Dracunculus Nematode; Eating; Female; Humans; Male
PubMed: 31996759
DOI: 10.1038/s41598-020-58191-4 -
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 -
Lancet (London, England) Feb 2021
Topics: Animals; Disease Eradication; Dracunculiasis; Dracunculus Nematode; Humans
PubMed: 33640060
DOI: 10.1016/S0140-6736(21)00262-2 -
Indian Journal of Dermatology,... 2023A nematode parasite, Dracunculus medinensis, causes dracunculiasis. Despite being non-fatal, this condition causes significant morbidity. Dracunculiasis is considered an...
A nematode parasite, Dracunculus medinensis, causes dracunculiasis. Despite being non-fatal, this condition causes significant morbidity. Dracunculiasis is considered an eradicated disease in India since 1999. We report two cases that document the unusual linear morphea-like morphology of the calcified D. medinensis and the rare periorbital location of the worm. The cases presented here are rare and a diagnostic challenge, considering the eradicated status of dracunculiasis.
Topics: Animals; Humans; Dracunculiasis; Dracunculus Nematode; India; Skin Diseases
PubMed: 33969654
DOI: 10.25259/IJDVL_909_20 -
The American Journal of Tropical... Feb 2021The 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...
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.
Topics: Animals; Animals, Domestic; Chad; Dog Diseases; Dogs; Dracunculiasis; Dracunculus Nematode; Family Characteristics; Female; Male; Parasite Load; Regression Analysis; Risk Factors
PubMed: 33617473
DOI: 10.4269/ajtmh.19-0924 -
Applied and Environmental Microbiology May 2018The adjustment of metabolic patterns is fundamental to fungal biology and plays vital roles in adaptation to diverse ecological challenges. Nematode-trapping fungi can...
The adjustment of metabolic patterns is fundamental to fungal biology and plays vital roles in adaptation to diverse ecological challenges. Nematode-trapping fungi can switch their lifestyle from saprophytic to pathogenic by developing specific trapping devices induced by nematodes to infect their prey as a response to nutrient depletion in nature. However, the chemical identity of the specific fungal metabolites used during the switch remains poorly understood. We hypothesized that these important signal molecules might be volatile in nature. Gas chromatography-mass spectrometry was used to carry out comparative analysis of fungal metabolomics during the saprophytic and pathogenic lifestyles of the model species Two media commonly used in research on this species, cornmeal agar (CMA) and potato dextrose agar (PDA), were chosen for use in this study. The fungus produced a small group of volatile furanone and pyrone metabolites that were associated with the switch from the saprophytic to the pathogenic stage. fungi grown on CMA tended to produce more traps and employ attractive furanones to improve the utilization of traps, while fungi grown on PDA developed fewer traps and used nematode-toxic furanone metabolites to compensate for insufficient traps. Another volatile pyrone metabolite, maltol, was identified as a morphological regulator for enhancing trap formation. Deletion of the gene in led to increased amounts of the furanone attractant (2-fold) in mutants and enhanced the attractive activity (1.5-fold) of the fungus, while it resulted in decreased trap formation. This investigation provides new insights regarding the comprehensive tactics of fungal adaptation to environmental stress, integrating both morphological and metabolomic mechanisms. Nematode-trapping fungi are a unique group of soil-living fungi that can switch from the saprophytic to the pathogenic lifestyle once they come into contact with nematodes as a response to nutrient depletion. In this study, we investigated the metabolic response during the switch and the key types of metabolites involved in the interaction between fungi and nematodes. Our findings indicate that develops multiple and flexible metabolic tactics corresponding to different morphological responses to nematodes. can use similar volatile furanone and pyrone metabolites with different ecological functions to help capture nematodes in the fungal switch from the saprophytic to the pathogenic lifestyle. Furthermore, studies with mutants with increased furanone and pyrone metabolites confirmed the results. This investigation reveals the importance of volatile signaling in the comprehensive tactics used by nematode-trapping fungi, integrating both morphological and metabolomic mechanisms.
Topics: Animals; Ascomycota; Dracunculus Nematode; Food Chain; Gas Chromatography-Mass Spectrometry; Metabolome; Metabolomics; Morphogenesis; Signal Transduction; Volatile Organic Compounds
PubMed: 29453265
DOI: 10.1128/AEM.02749-17 -
Parasites & Vectors Jul 2015Despite being certified guinea worm free in 2007, Cameroon continues surveillance efforts to ensure rapid verification of any suspected reoccurrence. This includes the...
BACKGROUND
Despite being certified guinea worm free in 2007, Cameroon continues surveillance efforts to ensure rapid verification of any suspected reoccurrence. This includes the investigation of every rumor and confirmation of each suspicious expulsed worm. This paper presents fieldwork carried out to investigate a guinea worm rumor in Cameroon which turned out to be an Onchocerca volvulus mimicking Dracunculus medinensis.
METHODS
The investigation included a field visit to the subsistence farming community where the rumor was reported. During the visit, interviews were conducted with health staff who managed the case and the elderly farmer from whom the worm was retrieved. An investigation of any potential missed guinea worm cases was also conducted through interviews with community residents and reviews of the health facility's medical records. This was combined with laboratory analyses of water samples from the community's water sources and the retrieved worm which was removed from the patient via wrapping it around a stick.
RESULTS
Microscopy and molecular analyses of the retrieved worm revealed a female Onchocerca volvulus whose expulsion strongly mimicked guinea worm. In addition to presenting findings of our investigation, this paper discusses distinguishing elements between the two parasites and gives an overview of guinea worm eradication efforts in Cameroon as well as current challenges to the worm's eradication globally.
CONCLUSIONS
The investigation findings suggest the evolving Onchocerca volvulus worm tropisms' adaptive survival behavior worth further investigation. Strategies used to successfully control guinea worm in Cameroon could be adapted for Onchocerca volvulus control.
Topics: Aged; Animals; Cameroon; Diagnosis, Differential; Dracunculiasis; Dracunculus Nematode; Farms; Female; Humans; Onchocerca volvulus; Onchocerciasis; Travel; Water
PubMed: 26178636
DOI: 10.1186/s13071-015-1004-1