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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... 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 -
International Journal of Infectious... Apr 2021Guinea worm (GW) disease, caused by Dracunculus medinensis, is an almost eradicated waterborne zoonotic disease. The World Health Organization (WHO) currently lists GW...
Guinea worm (GW) disease, caused by Dracunculus medinensis, is an almost eradicated waterborne zoonotic disease. The World Health Organization (WHO) currently lists GW as endemic in only five African countries. In July 2020, the Vietnamese public health surveillance system detected a hanging worm in a 23-year-old male patient, who did not report any travel to Africa or any country previously endemic for GW. The patient was hospitalized with symptoms of fatigue, anorexia, muscle aches, and abscesses, with worms hanging out of the skin in the lower limbs. The worms were retrieved from the lesions and microscopically examined in Vietnam, identifying structures compatible with Dracunculus spp. and L1-type larvae. A section of this parasite was sent to the Centers for Disease Control and Prevention (CDC) in Atlanta, United States, for confirmatory diagnosis of GW. The adult worm had cuticle structures compatible with Dracunculus parasites, although the length of L1 larvae was about 339 μm, substantially shorter than D. medinensis. DNA sequence analysis of the 18S small subunit rRNA gene confirmed that this parasite was not GW, and determined that the sample belonged to a Dracunculus sp. not previously reported in GenBank that clustered with the animal-infective Dracunculus insignis and Dracunculus lutrae, located in a different clade than D. medinensis. This study highlights the importance of effective public health surveillance systems and the collaborative work of local public health authorities from Vietnam with the WHO and CDC in efforts to achieve the eradication of GW.
Topics: Animals; Anthelmintics; Dracunculiasis; Dracunculus Nematode; Humans; Larva; Male; Public Health Surveillance; Thiabendazole; Treatment Outcome; Vietnam; Waterborne Diseases; Young Adult
PubMed: 33737138
DOI: 10.1016/j.ijid.2021.02.018 -
Lancet (London, England) Feb 2021
Topics: Animals; Disease Eradication; Dracunculiasis; Dracunculus Nematode; Humans
PubMed: 33640060
DOI: 10.1016/S0140-6736(21)00262-2 -
Parasitology Research Dec 2023Nematode species of the genus Dracunculus (Spirurida: Dracunculoidea) infect tissues and body cavities of reptiles, domestic and wild carnivores, and humans. The...
Nematode species of the genus Dracunculus (Spirurida: Dracunculoidea) infect tissues and body cavities of reptiles, domestic and wild carnivores, and humans. The definitive hosts acquire the infection by ingesting intermediate (i.e., cyclopoid copepod) or paratenic (i.e., amphibians and fishes) hosts. Here we report the jaguar (Panthera onca) as a potential new host for Dracunculus sp. The nematode was collected from an ulcerated cutaneous nodule on the left anterior limb of a female jaguar in the municipality of Miranda, Mato Grosso do Sul state, Brazil. Based on the morphology of first stage larvae collected from a small fragment of the uterus of the adult nematode, the species was identified as Dracunculus sp. Reichard, 1759. Additionally, the morphological identification was molecularly confirmed by sequencing the cox1 gene. This report advocates for further investigations into the transmission cycle of this parasite in the Brazilian Pantanal wetland, considering the role of wildlife hosts and the zoonotic potential of Dracunculus species in that area.
Topics: Animals; Humans; Female; Panthera; Animals, Wild; Dracunculus Nematode; Dracunculoidea; Fishes; Brazil
PubMed: 37823992
DOI: 10.1007/s00436-023-07984-3 -
PLoS Neglected Tropical Diseases Mar 2021Guinea 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...
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.
Topics: Adult; Animals; Chad; Dog Diseases; Dogs; Dracunculiasis; Dracunculus Nematode; Female; Health Knowledge, Attitudes, Practice; Humans; Male; Middle Aged; Patient Education as Topic; Primary Prevention; Surveys and Questionnaires
PubMed: 33735242
DOI: 10.1371/journal.pntd.0009285 -
Medical History Apr 2023Guinea worm disease (dracunculiasis) is a debilitating waterborne disease. Once widespread, it is now on the brink of eradication. However, the Guinea Worm Eradication...
Guinea worm disease (dracunculiasis) is a debilitating waterborne disease. Once widespread, it is now on the brink of eradication. However, the Guinea Worm Eradication Programme (GWEP), like guinea worm itself, has been under-studied by historians. The GWEP demonstrates an unusual model of eradication, one focused on primary healthcare (PHC), community participation, health education and behavioural change (safe drinking). The PHC movement collided with a waterborne disease, which required rapid but straightforward treatment to prevent transmission, creating a historical space for the emergence of village-based volunteer health workers, as local actors realigned global health policy on a local level. These Village Volunteers placed eradication in the hands of residents of endemic areas, epitomising the participation-focused nature of the GWEP. This participatory mode of eradication highlights the agency of those in endemic areas, who, through volunteering, safe drinking and community self-help, have been the driving force behind dracunculiasis eradication. In the twenty-first century, guinea worm has become firstly a problem of human mobility, as global health has struggled to contain cases in refugees and nomads, and latterly a zoonotic disease, as guinea worm has shifted hosts to become primarily a parasite of dogs. This demonstrates both the potential of One Health approaches and the need for One Health to adopt from PHC and the GWEP a focus on the health of humans and animals in isolated and impoverished areas. Guinea worm demonstrates how the biological and the historical interact, with the GWEP and guinea worm shaping each other over the course of the eradication programme.
Topics: Humans; Animals; Dogs; Dracunculus Nematode; Dracunculiasis; Waterborne Diseases; Health Education; Health Policy; Disease Eradication
PubMed: 37525460
DOI: 10.1017/mdh.2023.18 -
International Health Dec 2021
Topics: Disease Eradication; Global Health; Humans
PubMed: 34532741
DOI: 10.1093/inthealth/ihab055 -
International Journal For Parasitology.... Aug 2021Parasitic nematodes in the genus have a complex life cycle that requires more than one host species in both aquatic and terrestrial habitats. The most well-studied...
Parasitic nematodes in the genus have a complex life cycle that requires more than one host species in both aquatic and terrestrial habitats. The most well-studied species, , is the causative agent of human Guinea worm disease (dracunculiasis). There are several other species that infect non-human animals, primarily wildlife (reptiles and mammals). The classic route of transmission to humans is through the ingestion of water containing the intermediate host, a cyclopoid copepod, infected with third-stage larvae (L3s). However, many animal hosts (e.g., terrestrial snakes, dogs) of other sp. appear unlikely to ingest a large number of copepods while drinking. Therefore, alternative routes of infection (e.g., paratenic or transport hosts) may facilitate transmission to these species. To better understand the role of paratenic and transport hosts in transmission to animal definitive hosts, we compared copepod ingestion rates for aquatic species (fish, frogs [tadpoles and adults], and newts) which may serve as paratenic or transport hosts. We hypothesized that fish would consume more copepods than amphibians. Our findings confirm that African clawed frogs () and fish consume copepods, but that fish ingest, on average, significantly higher numbers (68% [34/50]) than adult African clawed frogs (36% [18/50]) during a 24-h time period. Our results suggest that amphibians and fish may play a role in the transmission of to definitive hosts. Still, additional research is required to determine whether, in the wild, fish or frogs are serving as paratenic or transport hosts. If so, they may facilitate transmission. However, if these animals simply act as dead-end hosts or as means of copepod population control, they may decrease transmission.
PubMed: 34189031
DOI: 10.1016/j.ijppaw.2021.06.001 -
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