Human infection with an unknown species of Dracunculus in Vietnam.

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.

Dracunculiasis in a domestic dog in Brazil.

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.

Population genomic evidence that human and animal infections in Africa come from the same populations of Dracunculus medinensis.

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.

Dracunculus Species in Meso-mammals from Georgia, United States, and Implications for the Guinea Worm Eradication Program in Chad, Africa.

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.

Guinea worm in domestic dogs in Chad: A description and analysis of surveillance data.

After a ten-year absence of reported Guinea worm disease in Chad, human cases were rediscovered in 2010, and canine cases were first recorded in 2012. In response, active surveillance for Guinea worm in both humans and animals was re-initiated in 2012. As of 2018, the Chad Guinea Worm Eradication Program (CGWEP) maintains an extensive surveillance system that operates in 1,895 villages, and collects information about worms, hosts (animals and humans), and animal owners. This report describes in detail the CGWEP surveillance system and explores epidemiological trends in canine Guinea worm cases during 2015-2018. Our results showed an increased in the number of canine cases detected by the system during the period of interest. The proportion of worms that were contained (i.e., water contamination was prevented) improved significantly over time, from 72.8% in 2015 to 85.7% in 2018 (Mantel-Haenszel chi-square = 253.3, P < 0.0001). Additionally, approximately 5% of owners of infected dogs reported that the dog had a Guinea worm-like infection earlier that year; 12.6% had a similar worm in a previous year. The proportion of dogs with a history of infection in a previous year increased over time (Mantel-Haenszel chi-square = 18.8, P < 0.0001). Canine cases were clustered in space and time: most infected dogs (80%) were from the Chari Baguirmi (38.1%) and Moyen Chari Regions (41.9%), and for each year the peak month of identified canine cases was June, with 78.5% occurring during March through August. Findings from this report evoke additional questions about why some dogs are repeatedly infected. Our results may help to target interventions and surveillance efforts in terms of space, time, and dogs susceptible to recurrent infection, with the ultimate goal of Guinea worm eradication.

Population genetic analysis of Chadian Guinea worms reveals that human and non-human hosts share common parasite populations.

Following almost 10 years of no reported cases, Guinea worm disease (GWD or dracunculiasis) reemerged in Chad in 2010 with peculiar epidemiological patterns and unprecedented prevalence of infection among non-human hosts, particularly domestic dogs. Since 2014, animal infections with Guinea worms have also been observed in the other three countries with endemic transmission (Ethiopia, Mali, and South Sudan), causing concern and generating interest in the parasites' true taxonomic identity and population genetics. We present the first extensive population genetic data for Guinea worm, investigating mitochondrial and microsatellite variation in adult female worms from both human and non-human hosts in the four endemic countries to elucidate the origins of Chad's current outbreak and possible host-specific differences between parasites. Genetic diversity of Chadian Guinea worms was considerably higher than that of the other three countries, even after controlling for sample size through rarefaction, and demographic analyses are consistent with a large, stable parasite population. Genealogical analyses eliminate the other three countries as possible sources of parasite reintroduction into Chad, and sequence divergence and distribution of genetic variation provide no evidence that parasites in human and non-human hosts are separate species or maintain isolated transmission cycles. Both among and within countries, geographic origin appears to have more influence on parasite population structure than host species. Guinea worm infection in non-human hosts has been occasionally reported throughout the history of the disease, particularly when elimination programs appear to be reaching their end goals. However, no previous reports have evaluated molecular support of the parasite species identity. Our data confirm that Guinea worms collected from non-human hosts in the remaining endemic countries of Africa are Dracunculus medinensis and that the same population of worms infects both humans and dogs in Chad. Our genetic data and the epidemiological evidence suggest that transmission in the Chadian context is currently being maintained by canine hosts.

Pattern of infection with Parapharyngodon riojensis Ramallo, Bursey, Goldberg 2002 (Nematoda: Pharyngodonidae) in the lizard Phymaturus extrilidus from Puna region, Argentina

The pattern of infection with the nematode Parapharyngodon riojensis in the lizard Phymaturus extrilidus in a Puna area, central-west Argentina was studied. No significant prevalence differences were found between sexes or seasons sampled. However, there were differences in mean intensity between the summer (dry period) and autumn (wet period) seasons. Mean intensity was higher in the moistest season, associated with low body condition in P. extrilidus. The genus Parapharyngodon has a direct life cycle, and environmental moisture could favor higher intensity in the rainy period. The present study provides the first data on the parasitic ecology of P. extrilidus from Argentina.

Guinea Worm (Dracunculus medinensis) Infection in a Wild-Caught Frog, Chad.

A third-stage (infective) larva of Dracunculus medinensis, the causative agent of Guinea worm disease, was recovered from a wild-caught Phrynobatrachus francisci frog in Chad. Although green frogs (Lithobates clamitans) have been experimentally infected with D. medinensis worms, our findings prove that frogs can serve as natural paratenic hosts.

Emergence of Onchocerca volvulus from skin mimicking Dracunculiasis medinensis.

We describe 11 cases of suspected Dracunculus medinensis infection in which the worm recovered was identified as Onchocerca volvulus. Identification was based on morphology of the examined specimen.

[Non-indigenous and non-specific parasitic nematodes--the background and the consequences]. / Zawleczone i niespecyficzne nicienie pasozytnicze--przyczyny i skutki.

Introduction of the host is the main reason behind introduction of the parasite, e. g., nematodes. The introduction of the Japanese eel (Anguilla japonica) in Europe in the 1980s resulted in expansion of the swimbladder nematode Anguillicola crassus which soon invaded not only populations of the European eel (A. anguilla), but also other local fish. The raccoon (Procyon lotor) is native to North America. It is the specific host of Strongyloides procyonis and Baylisascaris procyonis. More than 90 species of wild and domestical bird and mammal species, including humans, have been infected with B. procyonis larvae. The larvae enter various organs of paratenic hosts, particularly the central nervous system and eye, causing severe diseases and death. Asthworthius sidemi--a blood-succking, abomasal nematode, a specific parasite of the Asiatic sika deer (Cervus nippon) and sambar deer (C. unicolor)--was first introduced with its hosts into countries adjacent to Poland. A. sidemi is especially dangerous to the European bison (Bison bonasus) which is its new host. The bison populations, in both Bialowieza Primaeval Forest and the Bieszczady Mts, sometimes show a 100% prevalence and mass infection intensity. Imported animals, sold in pet shops or available from private breeding firms, often carry non-native parasites. For example, the red-eared tortoise (Trachemys scripta elegans) and Afgan tortoise (Agrionemys horsfieldii) carry nematodes Angusticaecum holopterum, Tachygonetria lobata and T. robusta. Migratory birds in their wintering grounds are often infected with parasites which are usually not constant components of the native fauna, but sometimes nematodes could find a suitable conditions to complete their life cycle. E.g. Cyathosoma microspiculum, species specific to cormorants (Phalacrocorax carbo) and previously recorded only from Asia and the Asian-European boudary, was able complete the life cycle in Poland. The increasingly frequent travels to countries with different climatic conditions contribute to introduction of non-native nematodes: Dirofilaria immitis--in dogs, D. repens or Ancylostoma brasiliense--in humans.

Reporte de un caso de dracunculosis en un canino en la provincia de Formosa - Argentina / Dracunculiasis in a dog in Formosa - Argentina : case report

Se comunica el hallazgo de Dracunculus sp. en un canino proveniente de la localidade de Fontana, Departamento Patino, provincia de Formosa, Argentina. El hallazgo constituye el cuarto caso de Dracunculosis registrado en animales en una misma area geografica de Formosa.