Understanding the transmission of Mycobacterium ulcerans: A step towards controlling Buruli ulcer

Mycobacterium ulcerans is the causative agent of Buruli ulcer, a rare but chronic debilitating skin and soft tissue disease found predominantly in West Africa and Southeast Australia. While a moderate body of research has examined the distribution of M. ulcerans, the specific route(s) of transmission of this bacterium remain unknown, hindering control efforts. M. ulcerans is considered an environmental pathogen given it is associated with lentic ecosystems and human-to-human spread is negligible. However, the pathogen is also carried by various mammals and invertebrates, which may serve as key reservoirs and mechanical vectors, respectively. Here, we examine and review recent evidence from these endemic regions on potential transmission pathways, noting differences in findings between Africa and Australia, and summarising the risk and protective factors associated with Buruli ulcer transmission. We also discuss evidence suggesting that environmental disturbance and human population changes precede outbreaks. We note five key research priorities, including adoption of One Health frameworks, to resolve transmission pathways and inform control strategies to reduce the spread of Buruli ulcer.     

Endemic infection reduces transmission potential of an epidemic parasite during co-infection

Endemic, low-virulence parasitic infections are common in nature. Such infections may deplete host resources, which in turn could affect the reproduction of other parasites during co-infection. We aimed to determine whether the reproduction, and therefore transmission potential, of an epidemic parasite was limited by energy costs imposed on the host by an endemic infection. Total lipids, triacylglycerols (TAG) and polar lipids were measured in cockroaches (Blattella germanica) that were fed ad libitum, starved or infected with an endemic parasite, Gregarina blattarum. Reproductive output of an epidemic parasite, Steinernema carpocapsae, was then assessed by counting the number of infective stages emerging from these three host groups. We found both starvation and gregarine infection reduced cockroach lipids, mainly through depletion of TAG. Further, both starvation and G. blattarum infection resulted in reduced emergence of nematode transmission stages. This is, to our knowledge, the first study to demonstrate directly that host resource depletion caused by endemic infection could affect epidemic disease transmission. In view of the ubiquity of endemic infections in nature, future studies of epidemic transmission should take greater account of endemic co-infections.     

The main sceneries of Chagas disease transmission. The vectors,blood and oral transmissions - A comprehensive review

This review deals with transmission of Trypanosoma cruzi by the most important domestic vectors, blood transfusion and oral intake. Among the vectors, Triatoma infestans, Panstrongylus megistus, Rhodnius prolixus, Triatoma dimidiata, Triatoma brasiliensis, Triatoma pseudomaculata, Triatoma sordida, Triatoma maculata, Panstrongylus geniculatus, Rhodnius ecuadoriensis and Rhodnius pallescens can be highlighted. Transmission of Chagas infection, which has been brought under control in some countries in South and Central America, remains a great challenge, particularly considering that many endemic countries do not have control over blood donors. Even more concerning is the case of non-endemic countries that receive thousands of migrants from endemic areas that carry Chagas disease, such as the United States of America, in North America, Spain, in Europe, Japan, in Asia, and Australia, in Oceania. In the Brazilian Amazon Region, since Shaw et al. (1969) described the first acute cases of the disease caused by oral transmission, hundreds of acute cases of the disease due to oral transmission have been described in that region, which is today considered to be endemic for oral transmission. Several other outbreaks of acute Chagas disease by oral transmission have been described in different states of Brazil and in other South American countries.     

Detection of anti-M. leprae antibodies in children in leprosy-endemic areas: A systematic review

BackgroundLeprosy elimination primarily targets transmission of Mycobacterium leprae which is not restricted to patients’ households. As interruption of transmission is imminent in many countries, a test to detect infected asymptomatic individuals who can perpetuate transmission is required. Antibodies directed against M. leprae antigens are indicative of M. leprae infection but cannot discriminate between active and past infection. Seroprevalence in young children, however, reflects recent M. leprae infection and may thus be used to monitor transmission in an area. Therefore, this literature review aimed to evaluate what has been reported on serological tests measuring anti-M. leprae antibodies in children without leprosy below the age of 15 in leprosy-endemic areas.Methods and findingsA literature search was performed in the databases Pubmed, Infolep, Web of Science and The Virtual Health Library. From the 724 articles identified through the search criteria, 28 full-text articles fulfilled all inclusion criteria. Two additional papers were identified through snowballing, resulting in a total of 30 articles reporting data from ten countries. All serological tests measured antibodies against phenolic glycolipid-I or synthetic derivatives thereof, either quantitatively (ELISA or UCP-LFA) or qualitatively (ML-flow or NDO-LID rapid test). The median seroprevalence in children in endemic areas was 14.9% and was stable over time if disease incidence remained unchanged. Importantly, seroprevalence decreased with age, indicating that children are a suitable group for sensitive assessment of recent M. leprae infection. However, direct comparison between areas, solely based on the data reported in these studies, was impeded by the use of different tests and variable cut-off levels.ConclusionsQuantitative anti-PGL-I serology in young children holds promise as a screening test to assess M. leprae infection and may be applied as a proxy for transmission and thereby as a means to monitor the effect of (prophylactic) interventions on the route to leprosy elimination.     

Molecular detection of Leishmania tropica in field caught Phlebotomus sand flies (Diptera: Psychodidae) from cutaneous leishmaniasis endemic focus of Pakistan

Cutaneous Leishmaniasis is endemic in tribal district Khyber for last more than one decade. The causative agent Leishmania tropica is known but sand fly species responsible for the transmission of disease still needs to be investigated. A total of 2647 Phlebotomus females belonging to 11 species were divided into 435 batches and subjected to PCR for detection of Leishmania in sand flies. A total of 50 batches belonging to three species i.e. Phlebotomus sergenti, Phlebotomus papatasi and Phlebotomus alexandri were detected positive for Leishmania tropica. Overall minimum infection rate was 1.89% (50/2647). Highest minimum infection rate of 2.11% (39/1710) was observed for Phlebotomus sergenti followed by 1.21% (8/661) for Phlebotomus paptasi and 1.82% (3/165) for Phlebotomus alexandri. Both blood fed (38%) and unfed (62%) sand flies were detected positive for the parasite DNA. Positive specimens were collected throughout the active season, from all collection sites of the study area. Detection of Leishmania parasite in multiple species of Phlebotomus indicates the possible role of these species as vector of disease in the tribal district Khyber of Pakistan. It also indicates the probable complex transmission cycle of the disease involving multiple vector species in the study area. Devising a control strategy by focusing on these vector species, may reduce the disease burden in the cutaneous leishmaniasis endemic tribal district Khyber.     

Molecular Characterization of Cryptosporidium spp. among Children in Rural Ghana

BackgroundThe relevance of Cryptosporidium infections for the burden of childhood diarrhoea in endemic settings has been shown in recent years. This study describes Cryptosporidium subtypes among symptomatic and asymptomatic children in rural Ghana to analyse subtype-specific demographic, geographical, seasonal and clinical differences in order to inform appropriate control measures in endemic areas.Conclusions/SignificanceCryptosporidiosis is characterized by seasonal anthroponotic transmission of strains typically found in Sub-Saharan Africa. The infection mainly affects young infants, with vomiting and diarrhoea being one of the leading symptoms in C. parvum infection. Combining molecular typing and clinical data provides valuable information for physicians and is able to track sources of infections.     

Mapping the Potential Risk of Mycetoma Infection in Sudan and South Sudan Using Ecological Niche Modeling

In 2013, the World Health Organization (WHO) recognized mycetoma as one of the neglected tropical conditions due to the efforts of the mycetoma consortium. This same consortium formulated knowledge gaps that require further research. One of these gaps was that very few data are available on the epidemiology and transmission cycle of the causative agents. Previous work suggested a soil-borne or Acacia thorn-prick-mediated origin of mycetoma infections, but no studies have investigated effects of soil type and Acacia geographic distribution on mycetoma case distributions. Here, we map risk of mycetoma infection across Sudan and South Sudan using ecological niche modeling (ENM). For this study, records of mycetoma cases were obtained from the scientific literature and GIDEON; Acacia records were obtained from the Global Biodiversity Information Facility. We developed ENMs based on digital GIS data layers summarizing soil characteristics, land-surface temperature, and greenness indices to provide a rich picture of environmental variation across Sudan and South Sudan. ENMs were calibrated in known endemic districts and transferred countrywide; model results suggested that risk is greatest in an east-west belt across central Sudan. Visualizing ENMs in environmental dimensions, mycetoma occurs under diverse environmental conditions. We compared niches of mycetoma and Acacia trees, and could not reject the null hypothesis of niche similarity. This study revealed contributions of different environmental factors to mycetoma infection risk, identified suitable environments and regions for transmission, signaled a potential mycetoma-Acacia association, and provided steps towards a robust risk map for the disease.     

Stochastic simulations of a multi-group compartmental model for Johne's disease on US dairy herds with test-based culling intervention

Infection elimination may be an important goal of control programs. Only in stochastic infection models can true infection elimination be observed as a fadeout. The phenomena of fadeout and variable prevalence are important in understanding the transmission dynamics of infectious diseases and these phenomena are essential to evaluate the effectiveness of control measures. To investigate the stochastic dynamics of Mycobacterium avium subsp. paratuberculosis (MAP) infection on US dairy herds with test-based culling intervention, we developed a multi-group stochastic compartmental model (a continuous time Markov chain model) with both horizontal and vertical transmission. The stochastic model predicted fadeout and within-herd prevalence to have a large variance. Although test-based culling intervention generally decreased prevalence over time, it took longer than desired by producers to eliminate the endemic MAP infection from a herd. Uncertainty analysis showed that, using annual culture test and culling of only high shedders or culling of both low and high shedders with a 12-month delay in culling of low shedders, MAP infection persisted in many herds beyond 20 years. While using semi-annual culture test and culling of low and high shedders with a 6-month delay in culling of low shedders, MAP infection in many herds would be extinct within 20 years. Sensitivity analysis of the cumulative density function of fadeout suggested that combining test-based culling intervention and reduction of transmission rates through improved management between susceptible calves and shedding animals may be more effective than either alone in eliminating endemic MAP infection. We also discussed the effects of other factors such as herd size, heifer replacement, and adult cow infection on the probability of fadeout.     

Cost-effectiveness evaluation of different control strategies for Clonorchis sinensis infection in a high endemic area of China: A modelling study

Clonorchiasis is an important food-borne parasitic disease caused by Clonorchis sinensis infection. The evaluation of long-term cost-effectiveness of control strategies is important for disease control and prevention. The present study aimed to assess the cost-effectiveness of the three recommended strategies (i.e., WHO, Chinese and Guangdong strategies) and different combinations of commonly used measures (i.e., preventive chemotherapy, information, education, and communication (IEC) and environmental improvement) on clonorchiasis. The study area, Fusha town in Guangdong Province, was a typical high endemic area in China. The analysis was based on a multi-group transmission model of C. sinensis infection. We set the intervention duration for 10 years and post-intervention period for 50 years. The corresponding costs and DALYs were estimated. Strategies with incremental cost-effectiveness ratios (ICERs) less than 1/5 of the willingness-to-pay threshold were identified as highly cost-effective strategies. The optimal control strategy was obtained using the next best comparator method. The ICERs of Guangdong strategy were $172 (95% CI: $143-$230) US for praziquantel and $106 (95% CI: $85-$143) US for albendazole, suggesting the highest cost-effectiveness among the three recommended strategies. For praziquantel, 470 sets of control strategies were identified as highly cost-effective strategies for achieving infection control (prevalence<5%). The optimal strategy consisted of chemotherapy targeted on at-risk population, IEC and environmental improvement, with coverages all being 100%, and with the ICER of $202 (95% CI: $168-$271) US. The results for transmission control (prevalence<1%) and albendazole were obtained with the same procedures. The findings may help to develop control policies for C. sinensis infection in high endemic areas. Moreover, the method adopted is applicable for assessment of optimal strategies in other endemic areas.     

Phylogeographical Studies of Ascaris spp. Based on Ribosomal and Mitochondrial DNA Sequences

Background

The taxonomic distinctiveness of Ascaris lumbricoides and A. suum, two of the world''s most significant nematodes, still represents a much-debated scientific issue. Previous studies have described two different scenarios in transmission patterns, explained by two hypotheses: (1) separated host-specific transmission cycles in highly endemic regions, (2) a single pool of infection shared by humans and pigs in non-endemic regions. Recently, A. suum has been suggested as an important cause of human ascariasis in endemic areas such as China, where cross-infections and hybridization have also been reported. The main aims of the present study were to investigate the molecular epidemiology of human and pig Ascaris from non-endemic regions and, with reference to existing data, to infer the phylogenetic and phylogeographic relationships among the samples.

Methodology

151 Ascaris worms from pigs and humans were characterized using PCR-RFLP on nuclear ITS rDNA. Representative geographical sub-samples were also analysed by sequencing a portion of the mitochondrial cox1 gene, to infer the extent of variability at population level. Sequence data were compared to GenBank sequences from endemic and non-endemic regions.

Principal Findings

No fixed differences between human and pig Ascaris were evident, with the exception of the Slovak population, which displays significant genetic differentiation. The RFLP analysis confirmed pig as a source of human infection in non-endemic regions and as a corridor for the promulgation of hybrid genotypes. Epidemiology and host-affiliation seem not to be relevant in shaping molecular variance. Phylogenetic and phylogeographical analyses described a complex scenario, involving multiple hosts, sporadic contact between forms and an ancestral taxon referable to A. suum.

Conclusions/Significance

These results suggest the existence of homogenizing gene flow between the two taxa, which appear to be variants of a single polytypic species. This conclusion has implications on the systematics, transmission and control programs relating to ascariasis.     

High Reinfection Rate after Preventive Chemotherapy for Fishborne Zoonotic Trematodes in Vietnam

Background

The World Health Organization aims for complete morbidity control of fishborne zoonotic trematodes (FZT) in endemic areas by 2020. The main intervention tool for achieving this goal is regular use of preventive chemotherapy by offering praziquantel to those at risk in endemic areas. The purpose of this study was to investigate the effectiveness of preventive chemotherapy to control FZT in an endemic area in Northern Vietnam.

Methodology and principle findings

We followed a cohort of 396 people who fulfilled the criteria for receiving preventive chemotherapy. Stool samples were examined by Kato-Katz technique for the presence of trematode eggs before, and two, 16, 29 and 60 weeks after preventive chemotherapy. The prevalence of trematode eggs in stool was 40.2% before, 2.3% two weeks after and increased to a cumulative prevalence of 29.8% sixty weeks after preventive chemotherapy.

Conclusions

The effectiveness of preventive chemotherapy as a main component in control of FZT is not well documented in most endemic areas. We found a high reinfection rate within the first year after preventive chemotherapy. Since these trematodes are zoonoses, preventive chemotherapy may not have sufficient impact alone on the transmission to have a lasting effect on the prevalence. Animal reservoirs and farm management practices must be targeted to achieve sustainable control of fishborne zoonotic trematode infections, hence control programs should consider a One Health approach.     

Dynamical behavior of a hepatitis B virus transmission model with vaccination

Hepatitis B virus (HBV) infection is a globally health problem. In 2005, the WHO Western Pacific Regional Office set a goal of reducing chronic HBV infection rate to less than 2% among children five years of age by 2012, as an interim milestone towards the final goal of less than 1%. Many countries made some plans (such as free HBV vaccination program for all neonates in China now) to control the transmission HBV. We develop a model to explore the impact of vaccination and other controlling measures of HBV infection. The model has simple dynamical behavior which has a globally asymptotically stable disease-free equilibrium when the basic reproduction number R₀≤1, and a globally asymptotically stable endemic equilibrium when R₀>1. Numerical simulation results show that the vaccination is a very effective measure to control the infection and they also give some useful comments on controlling the transmission of HBV.     

One Health: Past Successes and Future Challenges in Three African Contexts

Background

The recent emergence of zoonotic diseases such as Highly Pathogenic Avian Influenza (HPAI) and Severe Acute Respiratory Syndrome (SARS) have contributed to dominant Global Health narratives around health securitisation and pandemic preparedness, calling for greater co-operation between the health, veterinary and environmental sectors in the ever-evolving One Health movement. A decade later, One Health advocates face increasing pressure to translate the approach from theory into action.

Methodology/Principal Findings

A qualitative case study methodology was used to examine the emerging relationships between international One Health dialogue and its practical implementation in the African health policy context. A series of Key Informant Interviews (n = 32) with policy makers, government officials and academics in Nigeria, Tanzania and Uganda are presented as three separate case studies. Each case examines a significant aspect of One Health operationalisation, framed around the control of both emerging and Neglected Zoonotic Diseases including HPAI, Human African Trypanosomiasis and rabies. The research found that while there is general enthusiasm and a strong affirmative argument for adoption of One Health approaches in Africa, identifying alternative contexts away from a narrow focus on pandemics will help broaden its appeal, particularly for national or regionally significant endemic and neglected diseases not usually addressed under a “global” remit.

Conclusions/Significance

There is no ‘one size fits all’ approach to achieving the intersectoral collaboration, significant resource mobilisation and political co-operation required to realise a One Health approach. Individual country requirements cannot be underestimated, dismissed or prescribed in a top down manner. This article contributes to the growing discussion regarding not whether One Health should be operationalised, but how this may be achieved.     

Passive case detection for canine visceral leishmaniasis control in urban Brazil: Determinants of population uptake

BackgroundIn Brazil, the transmission of Leishmania infantum in urban settings is closely related to infection among dogs, with occasional transmission to humans. Serological screening of dogs for Leishmania spp. infection on requests of their owners (passive case detection) represents a frequent, but little studied, practice within the scope of Brazilian public health. This study identified factors associated with canine visceral leishmaniasis (CVL) diagnosis-seeking behavior of dog owners in Rondonópolis (236,000 inhabitants), a municipality in Central-Western Brazil where VL is endemic. Also, we evaluated the profile of dog owners and their animals screened on free demand.Methodology/Principal findingsUsing mixed effects negative binomial regression, we modelled the number of dogs screened for Leishmania infection on free demand per neighborhood from 2011 to 2016 as a function of time-dependent predictors (current or recent canine seropositivity and human VL incidence), distance to the screening site, and demographic variables. We assessed potential delays in the effect of time-dependent predictors on the outcome. Among 12,536 dogs screened for Leishmania infection, 64.2% were tested during serosurveys and 35.8% were tested on free demand. Of these, 63.9% were positive. Uptake of screening under free demand was strongly associated with higher levels of canine seropositivity in the neighborhood (current or recent) and decreasing distance to the screening site. A subsample of dog owners (n = 93) who sought CVL screening between 2016 and 2017 were interviewed in more detail. Owners with better socioeconomic status and dogs with apparent CVL clinical manifestations prevailed among them.Conclusions/SignificanceTo support timely CVL management, passive case detection along with awareness activities aimed at dog owners should be encouraged in endemic areas. Screening sites should be prioritized in accessible zones, as well as in socio-economically disadvantage areas. In parallel, CVL active case detection should be continued as a surveillance tool to guide control actions.     

Evidence in Sheep for Pre-Natal Transmission of Scrapie to Lambs from Infected Mothers

Natural scrapie transmission from infected ewes to their lambs is thought to occur by the oral route around the time of birth. However the hypothesis that scrapie transmission can also occur before birth (in utero) is not currently favoured by most researchers. As scrapie is an opportunistic infection with multiple infection routes likely to be functional in sheep, definitive evidence for or against transmission from ewe to her developing fetus has been difficult to achieve. In addition the very early literature on maternal transmission of scrapie in sheep was compromised by lack of knowledge of the role of the PRNP (prion protein) gene in control of susceptibility to scrapie. In this study we experimentally infected pregnant ewes of known PRNP genotype with a distinctive scrapie strain (SSBP/1) and looked for evidence of transmission of SSBP/1 to the offspring. The sheep were from the NPU Cheviot flock, which has endemic natural scrapie from which SSBP/1 can be differentiated on the basis of histology, genetics of disease incidence and strain typing bioassay in mice. We used embryo transfer techniques to allow sheep fetuses of scrapie-susceptible PRNP genotypes to develop in a range of scrapie-resistant and susceptible recipient mothers and challenged the recipients with SSBP/1. Scrapie clinical disease, caused by both natural scrapie and SSBP/1, occurred in the progeny but evidence (including mouse strain typing) of SSBP/1 infection was found only in lambs born to fully susceptible recipient mothers. Progeny were not protected from transmission of natural scrapie or SSBP/1 by washing of embryos to International Embryo Transfer Society standards or by caesarean derivation and complete separation from their birth mothers. Our results strongly suggest that pre-natal (in utero) transmission of scrapie may have occurred in these sheep.     

Establishing and Applying a Schistosomiasis Early Warning Index (SEWI) in the Lower Yangtze River Region of Jiangsu Province,China

Background

China has made remarkable progress in schistosomiasis control over the past decades. Transmission control has replaced morbidity control as the country moves towards the goal of elimination and the current challenge is to find a sensitive measure capable of gauging transmission risk in low-prevalence areas. The study aims to develop a Schistosomiasis Early Warning Index (SEWI) and demonstrate its use in Jiangsu Province along the lower Yangtze River.

Methodology/Principal Findings

The Delphi approach, a structured communication technique, was used to develop the SEWI. Two rounds of interviews with 30 public health experts specialized in schistosomiasis control were conducted using 40 indicators that reflected different aspects of schistosomiasis transmission and control. The necessity, feasibility, and sensitivity of each indicator were assessed and the weight value of each indicator determined based on these experts'' judgment. The system included 3 first-order indicators, 7 second-order indicators, and 30 third-order indicators. The 3 first-order indicators were endemic status, control measures, social and environmental factors, with the weight values 0.366, 0.343 and 0.291, respectively. For the 7 second-order indicators, the highest weight value was for control measures for snails (0.175) and the lowest for transmission route (0.110). We estimated and mapped the SEWI for endemic areas at the county scale in Jiangsu Province finding that the majority of the endemic areas were characterized as medium transmission risk (SEWI risk values between 0.3 and 0.6), while areas where transmission interruption had been officially declared showed SEWI values <0.30. A few isolated areas (e.g. endemic islands in the Yangtze River) produced SEWI values >0.60. These estimates are largely in agreement with the endemicity levels based on recent epidemiological surveys.

Conclusions/Significance

The SEWI should be useful for estimation of schistosomiasis transmission surveillance, particularly with reference to the elimination of the disease in China.     

Proof-of-Principle of Onchocerciasis Elimination with Ivermectin Treatment in Endemic Foci in Africa: Final Results of a Study in Mali and Senegal

Background

Mass treatment with ivermectin controls onchocerciasis as a public health problem, but it was not known if it could also interrupt transmission and eliminate the parasite in endemic foci in Africa where vectors are highly efficient. A longitudinal study was undertaken in three hyperendemic foci in Mali and Senegal with 15 to 17 years of annual or six-monthly ivermectin treatment in order to assess residual levels of infection and transmission, and test whether treatment could be safely stopped. This article reports the results of the final evaluations up to 5 years after the last treatment.

Methodology/Principal Findings

Skin snip surveys were undertaken in 131 villages where 29,753 people were examined and 492,600 blackflies were analyzed for the presence of Onchocerca volvulus larva using a specific DNA probe. There was a declining trend in infection and transmission levels after the last treatment. In two sites the prevalence of microfilaria and vector infectivity rate were zero 3 to 4 years after the last treatment. In the third site, where infection levels were comparatively high before stopping treatment, there was also a consistent decline in infection and transmission to very low levels 3 to 5 years after stopping treatment. All infection and transmission indicators were below postulated thresholds for elimination.

Conclusion/Significance

The study has established the proof of principle that onchocerciasis elimination with ivermectin treatment is feasible in at least some endemic foci in Africa. The study results have been instrumental for the current evolution from onchocerciasis control to elimination in Africa.     

Successful Control of Lymphatic Filariasis in the Republic of Korea

A successful experience of lymphatic filariasis control in the Republic of Korea is briefly reviewed. Filariasis in the Republic of Korea was exclusively caused by infection with Brugia malayi. Over the past several decades from the 1950s to 2006, many investigators exerted their efforts to detection, treatment, and follow-up of filariasis patients in endemic areas, and to control filariasis. Mass, combined with selective, treatments with diethylcarbamazine to microfilaria positive persons had been made them free from microfilaremia and contributed to significant decrease of the microfilarial density in previously endemic areas. Significant decrease of microfilaria positive cases in an area influenced eventually to the endemicity of filariasis in the relevant locality. Together with remarkable economic growth followed by improvement of environmental and personal hygiene and living standards, the factors stated above have contributed to blocking the transmission cycle of B. malayi and led to disappearance of this mosquito-borne ancient disease in the Republic of Korea.     

Multi-locus genotyping reveals established endemicity of a geographically distinct Plasmodium vivax population in Mauritania,West Africa

BackgroundPlasmodium vivax has been recently discovered as a significant cause of malaria in Mauritania, although very rare elsewhere in West Africa. It has not been known if this is a recently introduced or locally remnant parasite population, nor whether the genetic structure reflects epidemic or endemic transmission.Methodology/Principal findingsTo investigate the P. vivax population genetic structure in Mauritania and compare with populations previously analysed elsewhere, multi-locus genotyping was undertaken on 100 clinical isolates, using a genome-wide panel of 38 single nucleotide polymorphisms (SNPs), plus seven SNPs in drug resistance genes. The Mauritanian P. vivax population is shown to be genetically diverse and divergent from populations elsewhere, indicated consistently by genetic distance matrix analysis, principal components analyses, and fixation indices. Only one isolate had a genotype clearly indicating recent importation, from a southeast Asian source. There was no linkage disequilibrium in the local parasite population, and only a small number of infections appeared to be closely genetically related, indicating that there is ongoing genetic recombination consistent with endemic transmission. The P. vivax diversity in a remote mining town was similar to that in the capital Nouakchott, with no indication of local substructure or of epidemic population structure. Drug resistance alleles were virtually absent in Mauritania, in contrast with P. vivax in other areas of the world.Conclusions/SignificanceThe molecular epidemiology indicates that there is long-standing endemic transmission that will be very challenging to eliminate. The virtual absence of drug resistance alleles suggests that most infections have been untreated, and that this endemic infection has been more neglected in comparison to P. vivax elsewhere.