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Background Biological control programs involving Wolbachia-infected Aedes aegypti are currently deployed in different epidemiological settings. New Caledonia (NC) is an ideal location for the implementation and evaluation of such a strategy as the only proven vector for dengue virus (DENV) is Ae. aegypti and dengue outbreaks frequency and severity are increasing. We report the generation of a NC Wolbachia-infected Ae. aegypti strain and the results of experiments to assess the vector competence and fitness of this strain for future implementation as a disease control strategy in Noumea, NC. Methods/principal findings The NC Wolbachia strain (NC-wMel) was obtained by backcrossing Australian AUS-wMel females with New Caledonian Wild-Type (NC-WT) males. Blocking of DENV, chikungunya (CHIKV), and Zika (ZIKV) viruses were evaluated via mosquito oral feeding experiments and intrathoracic DENV challenge. Significant reduction in infection rates were observed for NC-wMel Ae. aegypti compared to WT Ae. aegypti. No transmission was observed for NC-wMel Ae. aegypti. Maternal transmission, cytoplasmic incompatibility, fertility, fecundity, wing length, and insecticide resistance were also assessed in laboratory experiments. Ae. aegypti NC-wMel showed complete cytoplasmic incompatibility and a strong maternal transmission. Ae. aegypti NC-wMel fitness seemed to be reduced compared to NC-WT Ae. aegypti and AUS-wMel Ae. aegypti regarding fertility and fecundity. However further experiments are required to assess it accurately. Conclusions/significance Our results demonstrated that the NC-wMel Ae. aegypti strain is a strong inhibitor of DENV, CHIKV, and ZIKV infection and prevents transmission of infectious viral particles in mosquito saliva. Furthermore, our NC-wMel Ae. aegypti strain induces reproductive cytoplasmic incompatibility with minimal apparent fitness costs and high maternal transmission, supporting field-releases in Noumea, NC., Author summary Dengue represents a risk for almost half of the world’s population, especially throughout the tropics. In New Caledonia, dengue outbreaks have become more frequent in the past decade along with the recent circulation of chikungunya and Zika viruses. The opportunity to use the biocontrol method involving the release of Wolbachia-infected Ae. aegypti mosquitoes has been investigated as an alternative solution to the traditional control methods, like elimination of larval habitats and pyrethroid insecticide application to kill adults, which are becoming insufficient. A local strain of Ae. aegypti carrying Wolbachia (NC-wMel) has been generated and tested to evaluate its pathogen blocking capacity for the four dengue virus serotypes as well as chikungunya and Zika viruses. The fitness of NC-wMel strain has also been assessed to estimate its ability to compete with the wild-type strain in the field. Noumea city, where a third of the population of New Caledonia resides, has been chosen as the first site to implement the method in New Caledonia. As Ae. aegypti is the only proven vector in New Caledonia, we expect a significant impact on dengue outbreaks occurring in Noumea as soon as a high frequency of NC-wMel is established in the population.

International audience; Nucleic acid testing during the preseroconversion viremic phase is required to differentially diagnose arboviral infections. The continuing emergence of arboviruses, such as Zika virus (ZIKV), dengue virus (DENV), and chikungunya virus (CHIKV), necessitates the development of a flexible diagnostic approach. Similar clinical signs and the priority to protect pregnant women from ZIKV infection indicate that the differential diagnosis of arboviruses is essential for effective patient management, clinical care, and epidemiologic surveillance. We describe an innovative diagnostic approach that combines generic RT-PCR amplification and identification by hybridization to specific probes. Original tetrathiolated probes were designed for the robust, sensitive, and specific detection of amplified arboviral genomes. The limit of detection using cultured and quantified stocks of whole viruses was 1 TCID50/mL for DENV-1, DENV-3, and CHIKV and 10 TCID50/mL for DENV-2, DENV-4, and ZIKV. The assay had 100% specificity with no false-positive results. The approach was evaluated using 179 human samples that previously tested as positive for the presence of ZIKV, DENV, or CHIKV genomes. Accordingly, the diagnostic sensitivity for ZIKV, DENV, and CHIKV was 87.88% (n = 58/66), 96.67% (n = 58/60), and 94.34% (n = 50/53), respectively. This method could be easily adapted to include additional molecular targets. Moreover, this approach may also be adapted to develop highly specific, sensitive, and easy to handle platforms dedicated to the multiplex screening and identification of emerging viruses.

International audience; Leptospirosis is a neglected tropical zoonosis caused by pathogenic spirochetes of the genus Leptospira. Infected reservoir animals, typically mice and rats, are asymptomatic, carry the pathogen in their renal tubules, and shed pathogenic spirochetes in their urine, contaminating the environment. Humans are accidental hosts of pathogenic Leptospira. Most human infections are mild or asymptomatic. However, 10% of human leptospirosis cases develop into severe forms, including high leptospiremia, multi-organ injuries, and a dramatically increased mortality rate, which can relate to a sepsis-like phenotype. During infection, the triggering of the inflammatory response, especially through the production of cytokines, is essential for the early elimination of pathogens. However, uncontrolled cytokine production can result in a cytokine storm process, followed by a state of immunoparalysis, which can lead to sepsis and associated organ failures. In this review, the involvement of cytokine storm and subsequent immunoparalysis in the development of severe leptospirosis in susceptible hosts will be discussed. The potential contribution of major pro-inflammatory cytokines in the development of tissue lesions and systemic inflammatory response, as well as the role of anti-inflammatory cytokines in contributing to the onset of a deleterious immunosuppressive cascade will also be examined. Data from studies comparing susceptible and resistant mouse models will be included. Lastly, a concise discussion on the use of cytokines for therapeutic purposes or as biomarkers of leptospirosis severity will be provided.

Background The Pacific Islands have environmental conditions highly favourable for transmission of leptospirosis, a neglected zoonosis with highest incidence in the tropics, and Oceania in particular. Recent reports confirm the emergence and outbreaks of leptospirosis in the Pacific Islands, but the epidemiology and drivers of transmission of human and animal leptospirosis are poorly documented, especially in the more isolated and less developed islands. Methodology/Principal findings We conducted a systematic review of human and animal leptospirosis within 25 Pacific Islands (PIs) in Polynesia, Melanesia, Micronesia, as well as Easter Island and Hawaii. We performed a literature search using four international databases for articles published between January 1947 and June 2017. We further included grey literature available on the internet. We identified 148 studies describing leptospirosis epidemiology, but the number of studies varied significantly between PIs. No data were available from four PIs. Human leptospirosis has been reported from 13 PIs, with 63% of all studies conducted in Hawaii, French Polynesia and New Caledonia. Animal leptospirosis has been investigated in 19 PIs and from 14 host species, mainly pigs (18% of studies), cattle (16%) and dogs (11%). Only 13 studies provided information on both human and animal leptospirosis from the same location. Serology results were highly diverse in the region, both in humans and animals. Conclusions/Significance Our study suggests that, as in other tropical regions, leptospirosis is widespread in the PIs while showing some epidemiological heterogeneity. Data are scarce or absent from many PIs. Rodents, cattle, pigs and dogs are all likely to be important carriers, but the relative importance of each animal species in human infection needs to be clarified. Epidemiological surveys with appropriate sampling design, pathogen typing and data analysis are needed to improve our understanding of transmission patterns and to develop effective intervention strategies., Author summary Leptospirosis is an important bacterial zoonosis that affects people and animals worldwide. It is common in tropical areas, especially in island ecosystems. Because islands are relatively small, isolated, and have limited health and diagnostic facilities, the disease burden is often underestimated. In this systematic review, we aimed to describe the extent of leptospirosis in the Pacific Islands, including the diversity of pathogens and animal reservoirs. We identified 148 studies from 21 Pacific islands that described Leptospira infection in humans or animals. In hospitalized febrile patients, leptospirosis was a common cause of the acute febrile illness, but accurate diagnosis was challenging and often delayed because symptoms overlapped with many other infectious diseases, and access to laboratory diagnosis was limited. A wide variety of animal hosts of Leptospira were identified, with rodents, cattle, pigs and dogs reported as important hosts; however, their relative importance in human infection remains unclear. Our review demonstrates that the epidemiology of leptospirosis varies across the Pacific Islands, but information about risk factors and transmission routes is currently limited. We recommend more integrated studies, using an eco-epidemiological approach that includes human, veterinary and environmental factors, and interactions between factors at different ecological scales.

International audience; Remote sensing can contribute to early warning for diseases with environmental drivers, such as flooding for leptospirosis. In this study we assessed whether and which remotely-sensed flooding indicator could be used in Cambodia to study any disease for which flooding has already been identified as an important driver, using leptospirosis as a case study. The performance of six potential flooding indicators was assessed by ground truthing. The Modified Normalized Difference Water Index (MNDWI) was used to estimate the Risk Ratio (RR) of being infected by leptospirosis when exposed to floods it detected, in particular during the rainy season. Chi-square tests were also calculated. Another variable-the time elapsed since the first flooding of the year-was created using MNDWI values and was also included as explanatory variable in a generalized linear model (GLM) and in a boosted regression tree model (BRT) of leptospirosis infections, along with other explanatory variables. Interestingly, MNDWI thresholds for both detecting water and predicting the risk of leptospirosis seroconversion were independently evaluated at -0.3. Value of MNDWI greater than -0.3 was significantly related to leptospirosis infection (RR = 1.61 [1.10-1.52]; χ2 = 5.64, p-value = 0.02, especially during the rainy season (RR = 2.03 [1.25-3.28]; χ2 = 8.15, p-value = 0.004). Time since the first flooding of the year was a significant risk factor in our GLM model (p-value = 0.042). These results suggest that MNDWI may be useful as a risk indicator in an early warning remote sensing tool for flood-driven diseases like leptospirosis in South East Asia.

Background Dengue is a mosquito-borne virus that causes extensive morbidity and economic loss in many tropical and subtropical regions of the world. Often present in cities, dengue virus is rapidly spreading due to urbanization, climate change and increased human movements. Dengue cases are often heterogeneously distributed throughout cities, suggesting that small-scale determinants influence dengue urban transmission. A better understanding of these determinants is crucial to efficiently target prevention measures such as vector control and education. The aim of this study was to determine which socioeconomic and environmental determinants were associated with dengue incidence in an urban setting in the Pacific. Methodology An ecological study was performed using data summarized by neighborhood (i.e. the neighborhood is the unit of analysis) from two dengue epidemics (2008–2009 and 2012–2013) in the city of Nouméa, the capital of New Caledonia. Spatial patterns and hotspots of dengue transmission were assessed using global and local Moran’s I statistics. Multivariable negative binomial regression models were used to investigate the association between dengue incidence and various socioeconomic and environmental factors throughout the city. Principal findings The 2008–2009 epidemic was spatially structured, with clusters of high and low incidence neighborhoods. In 2012–2013, dengue incidence rates were more homogeneous throughout the city. In all models tested, higher dengue incidence rates were consistently associated with lower socioeconomic status (higher unemployment, lower revenue or higher percentage of population born in the Pacific, which are interrelated). A higher percentage of apartments was associated with lower dengue incidence rates during both epidemics in all models but one. A link between vegetation coverage and dengue incidence rates was also detected, but the link varied depending on the model used. Conclusions This study demonstrates a robust spatial association between dengue incidence rates and socioeconomic status across the different neighborhoods of the city of Nouméa. Our findings provide useful information to guide policy and help target dengue prevention efforts where they are needed most., Author summary Dengue virus is rapidly spreading throughout tropical and subtropical regions worldwide, possibly aided by environmental change, urbanization and/or increase in human mobility. Already present in 120 countries, dengue virus causes extensive disease burden and generates large economic costs. As dengue is mosquito-borne, its transmission pattern is strongly influenced by climate. However, dengue cases are not always distributed evenly throughout cities, where climate can be assumed to be homogenous. This suggests that other factors which are heterogeneously distributed in cities could play a role in dengue transmission, such as socioeconomic status and environmental factors (both natural and built). Identifying those factors is crucial to develop and target dengue prevention interventions, such as mosquito control and education. Our study uses dengue incidence statistics from two large epidemics in Nouméa, the capital of New Caledonia, to investigate which socioeconomic or environmental factors correlate with dengue incidence in an urban setting. Dengue incidence was consistently higher in neighborhoods where socioeconomic status was lower (i.e. lower revenue or higher unemployment) and often higher where the proportion of single-family houses in all buildings was higher. Our data suggest that, if resources are limited, prevention measures should be targeted in priority towards neighborhoods of lower socioeconomic status.

International audience; Background: ESBL-producing Escherichia coli (ESBL-Ec) is considered a key indicator for antimicrobial resistance (AMR) epidemiological surveillance in animal, human and environment compartments. There is likelihood of ESBL-Ec animal-human transmission but proof of cross-compartment transmission is still unclear.Objectives: To characterize ESBL-Ec genetic similarity in various compartments (humans, animals and environment) from a rural area of Madagascar.Methods: We collected ESBL-Ec isolates prospectively from humans, animals and the environment (water) between April and October 2018. These isolates were subject to WGS and analysed with cutting-edge phylogenomic methods to characterize population genetic structure and infer putative transmission events among compartments.Results: Of the 1454 samples collected, 512 tested positive for ESBL-Ec. We successfully sequenced 510 samples, and a phylogenomic tree based on 179 365 SNPs was produced. Phylogenetic distances between and amongst compartments were indistinguishable, and 104 clusters of recent transmission events between compartments were highlighted. Amongst a large diversity of ESBL-Ec genotypes, no lineage host specificity was observed, indicating the regular occurrence of ESBL-Ec transfer among compartments in rural Madagascar.Conclusions: Our findings stress the importance of using a phylogenomic approach on ESBL-Ec samples in various putative compartments to obtain a clear baseline of AMR transmissions in rural settings, where one wants to identify risk factors associated with transmission or to measure the effect of 'One Health' interventions in low- and middle-income countries.

International audience; Leptospirosis is caused by pathogenic spirochetes of the genus Leptospira. Humans can be infected after exposure to contaminated urine of reservoir animals, usually rodents, regarded as typical asymptomatic carriers of leptospires. In contrast, accidental hosts may present an acute form of leptospirosis with a range of clinical symptoms including the development of Acute Kidney Injury (AKI). Chronic Kidney Disease (CKD) is considered as a possible AKI-residual sequela but little is known about the renal pathophysiology consequent to leptospirosis infection. Herein, we studied the renal morphological alterations in relation with the regulation of inflammatory cytokines and chemokines, comparing two experimental models of chronic leptospirosis, the golden Syrian hamster that survived the infection, becoming carrier of virulent leptospires, and the OF1 mouse, a usual reservoir of the bacteria. Animals were monitored until 28 days after injection with a virulent L. borgpetersenii serogroup Ballum to assess chronic infection. Hamsters developed morphological alterations in the kidneys with tubulointerstitial nephritis and fibrosis. Grading of lesions revealed higher scores in hamsters compared to the slight alterations observed in the mouse kidneys, irrespective of the bacterial load. Interestingly, pro-fibrotic TGF-β was downregulated in mouse kidneys. Moreover, cytokines IL-1β and IL-10, and chemokines MIP-1α/CCL3 and IP-10/CXCL-10 were significantly upregulated in hamster kidneys compared to mice. These results suggest a possible maintenance of inflammatory processes in the hamster kidneys with the infiltration of inflammatory cells in response to bacterial carriage, resulting in alterations of renal tissues. In contrast, lower expression levels in mouse kidneys indicated a better regulation of the inflammatory response and possible resolution processes likely related to resistance mechanisms.

Thyroid cancer incidence in New Caledonia is the highest reported in the world and is approximately 10-fold higher than in most developed countries. We describe the incidence patterns in this country according to histological and sociodemographic characteristics to give clues about potential etiologic factors. Another objective is to see whether the incidence figures are related to enhanced detection of small size carcinomas. The study included all 498 cases of thyroid cancer diagnosed in 1985-1999. Pathology reports were systematically reviewed to determine the histological type of the tumor and the size of the cancerous nodules. The incidence of carcinomas < or =10 mm was taken as an indicator of enhanced detection due to improved screening procedures. The age-standardized incidence rates in 1985-1999 were exceptionally high in Melanesian women (71.4/100,000) and men (10.4/100,000). The incidence increased three-fold in women from 1995 onwards. The increase in incidence was more striking for papillary carcinomas < or =10 mm than for large size carcinomas, but an increased incidence of carcinomas >10 mm was also observed among women. The analysis by municipality of residence in Melanesian women showed that the incidence was twice as high in 1995-1999 in the Loyalty Islands as in the rest of the country. The sharp increase of thyroid cancer incidence in 1985-1999 in New Caledonia was partly related to enhanced detection of small size carcinomas. The elevated incidence of thyroid cancers, as well as the ethnic and geographic disparities, may result from common environmental or lifestyle risk factors that need to be identified.

Background Dengue dynamics result from the complex interactions between the virus, the host and the vector, all being under the influence of the environment. Several studies explored the link between weather and dengue dynamics and some investigated the impact of climate change on these dynamics. Most attempted to predict incidence rate at a country scale or assess the environmental suitability at a global or regional scale. Here, we propose a new approach which consists in modeling the risk of dengue outbreak at a local scale according to climate conditions and study the evolution of this risk taking climate change into account. We apply this approach in New Caledonia, where high quality data are available. Methods We used a statistical estimation of the effective reproduction number (Rt) based on case counts to create a categorical target variable : epidemic week/non-epidemic week. A machine learning classifier has been trained using relevant climate indicators in order to estimate the probability for a week to be epidemic under current climate data and this probability was then estimated under climate change scenarios. Results Weekly probability of dengue outbreak was best predicted with the number of days when maximal temperature exceeded 30.8°C and the mean of daily precipitation over 80 and 60 days prior to the predicted week respectively. According to scenario RCP8.5, climate will allow dengue outbreak every year in New Caledonia if the epidemiological and entomological contexts remain the same. Conclusion We identified locally relevant climatic factor driving dengue outbreaks in New Caledonia and assessed the inter-annual and seasonal risk of dengue outbreak under different climate change scenarios up to the year 2100. We introduced a new modeling approach to estimate the risk of dengue outbreak depending on climate conditions. This approach is easily reproducible in other countries provided that reliable epidemiological and climate data are available.

Background. Group A Streptococcus (GAS)–related disease is responsible for high mortality and morbidity in the Pacific region. The high diversity of circulating strains in this region has hindered vaccine development due to apparently low vaccine coverage of type-specific vaccines. Method. Prospective passive surveillance of all GAS isolates in New Caledonia was undertaken in 2012 using emm typing and emm-cluster typing. Molecular data were compared with the results from a prior study undertaken in the same country and with data from 2 other Pacific countries, Fiji and Australia. Results. A high incidence of invasive infection was demonstrated at 43 cases per 100 000 inhabitants (95% confidence interval, 35–52 cases per 100 000 inhabitants). Three hundred eighteen GAS isolates belonging to 47 different emm types were collected. In Noumea, only 30% of the isolates recovered in 2012 belonged to an emm type that was present in the same city in 2006, whereas 69% of the isolates collected in 2012 belonged to an emm cluster present in 2006. When comparing New Caledonian, Australian, and Fijian data, very few common emm types were found, but 79%–86% of the isolates from each country belonged to an emm cluster present in all 3 countries. Avaccine that could protect against the 10 most frequent emm clusters in the Pacific region would potentially provide coverage ranging from 83% to 92%. Conclusions. This study confirms the high disease burden of GAS infection in New Caledonia and supports the added value of the emm-cluster typing system to analyze GAS epidemiology and to help inform global GAS vaccine formulation.

First identified in 1947, Zika virus took roughly 70 years to cause a pandemic unusually associated with virus-induced brain damage in newborns. Zika virus is transmitted by mosquitoes, mainly Aedes aegypti, and secondarily, Aedes albopictus, both colonizing a large strip encompassing tropical and temperate regions. As part of the international project ZIKAlliance initiated in 2016, 50 mosquito populations from six species collected in 12 countries were experimentally infected with different Zika viruses. Here, we show that Ae. aegypti is mainly responsible for Zika virus transmission having the highest susceptibility to viral infections. Other species play a secondary role in transmission while Culex mosquitoes are largely non-susceptible. Zika strain is expected to significantly modulate transmission efficiency with African strains being more likely to cause an outbreak. As the distribution of Ae. aegypti will doubtless expand with climate change and without new marketed vaccines, all the ingredients are in place to relive a new pandemic of Zika. Zika virus (ZIKV), the causative agent of virus-induced brain damage in newborns, is transmitted by mosquitoes, mainly Aedes aegypti, and secondarily, Aedes albopictus. Here, Obadia et al. characterize ZIKV vector competence of 50 mosquito populations from six species collected in 12 different countries to inform about epidemic risk. They find that African ZIKV strain shows higher transmission efficiency compared to American and Asian ZIKV strains and that Ae. aegypti mosquitoes have highest susceptibility to infections, while Culex mosquitoes are largely non-susceptible.

International audience; BACKGROUND: Helicobacter pylori is a major gastric bacterial pathogen, presumed to have established itself in the human stomach approximately 100,000 years ago. Helicobacter pylori co-evolved with its host, and human migrations shaped the expansion and the diversity of strains around the world. Here, we investigated the population structure and the genomic diversity of H. pylori in New Caledonia and Cambodia, where humans of different origins are living. METHODS: Both multilocus sequence typing (MLST) and macro-array experiments were performed to assess polymorphism of housekeeping genes and to compare differences in gene contents among strains of H. pylori. RESULTS: The macro-array analysis based on variations of the flexible gene pools was consistent with the contribution of ancestral H. pylori populations to modern strains. Most of the CDS variably present encode proteins of unknown function, selfish DNA, and transposases. In New Caledonia-where humans are of several ethnic origins-strains belonged to four different genetic populations, reflecting the diversity of human populations. Melanesians and Polynesians were infected mainly by strains assigned to hspMaori, whereas Caucasians were infected by hspWAfrica, hpEurope, and hpNEAfrica strains. In contrast, strains from Khmer patients belonged to only two subpopulations: hspEAsia and hpEurope. In the two countries, both ancient and recent human migrations may have influenced the diversity of H. pylori. CONCLUSION: Our present results are consistent with the possibility of admixture of strains in multiethnic communities. This increases the global polymorphism of H. pylori without evidence of functional change or impact on fitness and virulence.

BackgroundIncidence of acute rheumatic fever (ARF) and prevalence of rheumatic heart disease (RHD) in the Pacific region, including New Caledonia, are amongst the highest in the world. The main priority of long-term management of ARF or RHD is to ensure secondary prophylaxis is adhered to. The objectives of this study were to evaluate rates of adherence in people receiving antibiotic prophylaxis by intramuscular injections of penicillin in Lifou and to determine the factors associated with a poor adherence in this population.MethodsWe conducted a retrospective cohort study and we included 70 patients receiving injections of antibiotic prophylaxis to prevent ARF recurrence on the island of Lifou. Patients were classified as “good-adherent” when the rate of adherence was ≥80% of the expected injections and as “poor-adherent” when it was ResultsOur study showed that 46% of patients from Lifou receiving antibiotic prophylaxis for ARF or RHD had a rate of adherence ConclusionsTo improve adherence to secondary prophylaxis in Lifou, we therefore propose the following recommendations arising from the results of this study: i) identifying patients receiving antibiotic prophylaxis without medical history of ARF to strengthen their therapeutic education and ii) improving the medical coverage in patients with ARF or RHD. We also recommend that the nurse designated for the ARF prevention program in Lifou coordinate an active recall system based on an updated local register. But the key point to improve adherence among Melanesian patients is probably to give appropriate information regarding the disease and the treatment, taking into account the Melanesian perceptions of the disease.

Background Aedes (Stegomyia) albopictus is currently one of the most notorious globally invasive mosquito species. Its medical importance is well documented, and its fast expansion throughout most continents is being monitored with concern. It is generally assumed that its expansion through the Western Pacific island countries has not progressed since its establishment in Fiji in 1989. However, the current status of Ae. albopictus in the Pacific region is largely unknown. Findings According to data from the literature and our own observations, Ae. albopictus is currently present in the following countries of the southern Pacific region: Papua New Guinea, Solomon Islands, Fiji, and the Kingdom of Tonga, where it was first detected in July 2011. It is absent from New Caledonia and French Polynesia where routine entomological surveillance is carried out, and was not detected during entomological work in 2007, either on the Cook Islands or on the Wallis and Futuna Islands. The species was not reported from American Samoa in 2004, but it is mentioned as probably present in Vanuatu. This is the first report of Ae. albopictus in Tonga. Conclusions The introduction and establishment of Ae. albopictus in Tonga was expected due to the geographical proximity of this country to Fiji where the species is strongly established. The pathway of introduction is unknown. The expansion of Ae. albopictus in the Pacific region poses an increasing threat to public health given the role this mosquito plays as primary vector of emerging infectious diseases such as Chikungunya fever.

Background KSHV/HHV-8 is the etiological agent of Kaposi's sarcoma, primary effusion lymphoma and most multicentric Castleman's disease cases. KSHV exhibits a high genetic variability comprising five genotypes (A–E). Few data are yet available concerning the situation of KSHV, its genetic variability and the associated diseases in Melanesia. Objectives We performed a study on 626 natives Melanesians from New Caledonia and Vanikoro Island to evaluate KSHV seroprevalence and characterize molecularly the viral strains. Study design Plasma from 343 males and 283 females (age range: 15–86 years, mean age: 60) were tested for KSHV latent antibodies by an immunofluorescence assay (IFA) using BC-3 cells. DNAs extracted from peripheral blood buffy-coat of KSHV seropositive individuals were amplified to obtain a 737-bp fragment of the ORF-K1 gene. Phylogenetic analyses were then performed. Results Among 626 samples, 148 were IFA positive (dilution ≥ 1:80). The overall seroprevalence was 23.6% (25.2% in New Caledonia, 17.5% in Vanikoro). Fifteen (8 men and 7 women, mean age 69 years) out of 148 DNA samples were found PCR positive. All ORF-K1 sequences belonged to KSHV genotype D. A geographic clustering according to the island of origin of KSHV infected persons was clearly observed with sequences from New Caledonia clustering with most Vanuatu strains. Conclusions New Caledonia and Vanikoro are endemic for KSHV with a high diversity of genotype D variants. These strains were probably introduced into New Caledonia during multiple waves of migrations of Melanesian and Polynesian individuals that have colonized this archipelago.

Background Widespread but particularly incident in the tropics, leptospirosis is transmitted to humans directly or indirectly by virtually any Mammal species. However, rodents are recognized as the most important reservoir. In endemic regions, seasonal outbreaks are observed during hot rainy periods. In such regions, hot spots can be evidenced, where leptospirosis is “hyper-endemic”, its incidence reaching 500 annual cases per 100,000. A better knowledge of how rodent populations and their Leptospira prevalence respond to seasonal and meteorological fluctuations might help implement relevant control measures. Methodology/Principal Findings In two tribes in New Caledonia with hyper-endemic leptospirosis, rodent abundance and Leptospira prevalence was studied twice a year, in hot and cool seasons for two consecutive years. Highly contrasted meteorological situations, particularly rainfall intensities, were noted between the two hot seasons studied. Our results show that during a hot and rainy period, both the rodent populations and their Leptospira carriage were higher. This pattern was more salient in commensal rodents than in the sylvatic rats. Conclusions/Significance The dynamics of rodents and their Leptospira carriage changed during the survey, probably under the influence of meteorology. Rodents were both more numerous and more frequently carrying (therefore disseminating) leptospires during a hot rainy period, also corresponding to a flooding period with higher risks of human exposure to waters and watered soils. The outbreaks of leptospirosis in hyper-endemic areas could arise from meteorological conditions leading to both an increased risk of exposure of humans and an increased volume of the rodent reservoir. Rodent control measures would therefore be most effective during cool and dry seasons, when rodent populations and leptospirosis incidence are low., Author Summary In this study, we surveyed rodents and their Leptospira carriage in an area where human leptospirosis is hyper-endemic. We evidenced the well-known associations between specific rodent species and particular leptospires in both mice and rats. Overall, the observed Leptospira prevalence was in the range 18–47% depending on species, similar to other descriptions. However, significant variations were observed both in the abundance of rodents and their Leptospira carriage, one hot period with heavy rain being associated with both a highest abundance and an increased prevalence. Similar meteorological conditions could lead to increased leptospires dispersal by the rodent reservoir and increased exposure of humans to risk situations (e.g. flood, mud). Because rodent control measures were demonstrated elsewhere to be cost-effective if correctly planned and implemented, this contribution to a better knowledge of rodent and leptospires dynamics provides useful information and may in turn allow to develop relevant rodent control actions aimed at reducing the burden of human leptospirosis.

Leptospira interrogans is a bacterial species responsible for leptospirosis, a neglected worldwide zoonosis. Mice and rats are resistant and can become asymptomatic carriers, whereas humans and some other mammals may develop severe forms of leptospirosis. Uncommon among spirochetes, leptospires contain lipopolysaccharide (LPS) in their outer membrane. LPS is highly immunogenic and forms the basis for a large number of serovars. Vaccination with inactivated leptospires elicits a protective immunity, restricted to serovars with related LPS. This protection that lasts in mice, is not long lasting in humans and requires annual boosts. Leptospires are stealth pathogens that evade the complement system and some pattern recognition receptors from the Toll-like (TLR) and Nod-Like families, therefore limiting antibacterial defense. In macrophages, leptospires totally escape recognition by human TLR4, and escape the TRIF arm of the mouse TLR4 pathway. However, very little is known about the recognition and processing of leptospires by dendritic cells (DCs), although they are crucial cells linking innate and adaptive immunity. Here we tested the activation of primary DCs derived from human monocytes (MO-DCs) and mouse bone marrow (BM-DCs) 24h after stimulation with saprophytic or different pathogenic virulent or avirulent L. interrogans. We measured by flow cytometry the expression of DC-SIGN, a lectin involved in T-cell activation, co-stimulation molecules and MHC-II markers, and pro- and anti-inflammatory cytokines by ELISA. We found that exposure to leptospires, live or heat-killed, activated dendritic cells. However, pathogenic L. interrogans, especially from the Icterohaemorraghiae Verdun strain, triggered less marker upregulation and less cytokine production than the saprophytic Leptospira biflexa. In addition, we showed a better activation with avirulent leptospires, when compared to the virulent parental strains in murine BM-DCs. We did not observe this difference in human MO-DCs, suggesting a role for TLR4 in DC stimulation. Accordingly, using BM-DCs from transgenic deficient mice, we showed that virulent Icterohaemorraghiae and Manilae serovars dampened DC activation, at least partly, through the TLR4 and TRIF pathways. This work shows a novel bacterial immune evasion mechanism to limit DC activation and further illustrates the role of the leptospiral LPS as a virulence factor.

Dengue, Zika and chikungunya viruses cause significant human public health burdens in the world. These arboviruses are transmitted by vector mosquito species notably Aedes aegypti and Aedes albopictus. In the Pacific region, more vector species of arboviruses belonging to the Scutellaris Group are present. Due to the expansion of human travel and international trade, the threat of their dispersal in other world regions is on the rise. Strengthening of entomological surveillance ensuring rapid detection of introduced vector species is therefore required in order to avoid their establishment and the risk of arbovirus outbreaks. This surveillance relies on accurate species identification. The aim of this study was to assess the use of the Matrix-Assisted Laser Desorption Ionization Time-Of-Flight Mass Spectrometry (MALDI-TOF MS) as a tool for an international identification and surveillance of these mosquito vectors of arboviruses. Field-mosquitoes belonging to 8 species (Ae. aegypti, Ae. albopictus, Aedes polynesiensis, Aedes scutellaris, Aedes pseudoscutellaris, Aedes malayensis, Aedes futunae and Culex quinquefasciatus) from 6 countries in the Pacific, Asian and Madagascar, were included in this study. Analysis provided evidence that a MALDI-TOF database created using mosquitoes from the Pacific region allowed suitable identification of mosquito species from the other regions. This technic was as efficient as the DNA sequencing method in identifying mosquito species. Indeed, with the exception of two Ae. pseudoscutellaris, an exact species identification was obtained for all individual mosquitoes. These findings highlight that the MALDI-TOF MS is a promising tool that could be used for a global comprehensive arbovirus vector surveillance.

Compared to the previous 2013–2014 outbreak, dengue 2016–2017 outbreak in New Caledonia was characterized by an increased number of severe forms associated with hepatic presentations. In this study, we assessed the virological factors associated with this enhanced severity. Whole-genome sequences were retrieved from dengue virus (DENV)-1 strains collected in 2013–2014 and from severe and non-severe patients in 2016–2017. Fitness, hepatic tropism and cytopathogenicity of DENV 2016–2017 strains were compared to those of 2013–2014 strains using replication kinetics in the human hepatic cell line HuH7. Whole-genome sequencing identified four amino acid substitutions specific to 2016–2017 strains and absent from 2013–2014 strains. Three of these mutations occurred in predicted T cell epitopes, among which one was also a B cell epitope. Strains retrieved from severe forms did not exhibit specific genetic features. DENV strains from 2016–2017 exhibited a trend towards reduced replicative fitness and cytopathogenicity in vitro compared to strains from 2013–2014. Overall, the 2016–2017 dengue outbreak in New Caledonia was associated with a viral genetic evolution which had limited impact on DENV hepatic tropism and cytopathogenicity. These mutations, however, may have modified DENV strains antigenicity, altering the anti-DENV immune response in some patients, in turn favoring the development of severe forms. Trial registration: ClinicalTrials.gov identifier: NCT04615364.

Human herpesvirus 8 (HHV-8), also known as Kaposi’s arcoma (KS)-associated herpesvirus (KSHV), is the etioogical agent of all forms of Kaposi’s sarcoma, a tumor of ixed cellularity occurring frequently during human immundeficiency virus type 1 (HIV-1) infection (AIDS/epidemicS) and in transplant recipients (iatrogenic KS) (Boshoff nd Weiss, 2001; Hengge et al., 2002). Such tumor also ccurs among non-HIV-infected individuals, predominantly ither in aged men of Mediterranean and Middle East oriins (classic KS) or in inhabitants from East and Central frica (endemic KS) (Boshoff and Weiss, 2001; Hengge et l., 2002). Clinically, KS is mainly characterized by skin lesions of arious aspects including macules, papules and/or nodules, hich are mainly localized on the lower limbs in the classic orm. However, disseminated skin lesions, with lymph-node

International audience; Human T-cell lymphotropic virus type 1 (HTLV-1)-associated adult T-cell leukemia/lymphoma (ATLL) has a poor prognosis owing to its intrinsic resistance to chemotherapy. Although zidovudine (AZT) and alpha interferon (IFN-alpha) give rise to some response and improve the prognosis of ATLL, alternative therapies are needed. Arsenic trioxide (As(2)O(3)) has been shown to synergize with IFN-alpha in arresting cell growth and inducing apoptosis of ATLL cells in vitro. In this study, we evaluated the toxicity and the efficacy of this combined treatment in HTLV-1-infected squirrel monkeys (Saimiri sciureus) and HTLV-1 infected cell lines derived therefrom. We first show that treatment with As(2)O(3) and IFN-alpha can induce growth arrest in HTLV-1-transformed monkey T-cell lines in vitro. We then show that treatment of squirrel monkeys with As(2)O(3) in vivo is highly toxic at 0.9 or 0.3mg/day but not at 0.14mg/day for up to 2 weeks. Although the combination of As(2)O(3) and IFN-alpha did not affect significantly the HTLV-1 proviral load in infected monkeys, it reduced the absolute numbers of CD3(+), CD4(+) and CD8(+) cells during treatment, with a significant reduction in the total number of circulating HTLV-1 flower cells in the infected monkeys with chronic ATLL-like disease.

International audience; Mostly studied as a zoonosis, leptospirosis is also an environment-borne infection and most human cases originate from soil or water contaminations. Yet, only few studies have been interested in the survival of pathogenic Leptospira in freshwater. In this study, water microcosms were designed to evaluate the survival and virulence of Leptospira spp. for 2 years. Four commercial bottled drinking waters and a non-ionized water, all previously filter-sterilized, were studied. Either one of two Leptospira interrogans strains, one Leptospira borgpetersenii strain, or a saprophytic Leptospira biflexa was inoculated in these waters under nutrient-deprived conditions. Molecular, microscopic and cultural approaches were used to study Leptospira survival. Direct virulence of the pathogens was assessed using animal challenge without re-culturing. Our results confirmed the capacity of pathogenic Leptospira to survive for more than a year in water. In addition, we showed the ability of L. interrogans in nutrient-deprived conditions to directly cause systemic infection in susceptible animals. To our knowledge, this is the first report of direct infection of a susceptible host with Leptospira following a long starvation and survival period in nutrient-deprived water. Our results also suggest that Leptospira turned into a physiological "survival" state in harsh freshwater conditions. These data are of prime importance considering that freshwater is a major source of Leptospira infections. Environmental survival and virulence of pathogenic Leptospira spp. are becoming a crucial challenge to determine the environmental risk and adopt relevant prevention and control strategies.

Leptospirosis is endemic in New Caledonia. Clinical diagnosis is often difficult and its evolution can be fatal. Leptospirosis requires specific management before biological confirmation. Modified Faine criteria (Faine Score) have been suggested to diagnose leptospirosis on epidemiological (parts A and B) and biological (part C) criteria. The main objective of our study was to assess the relevance of the epidemiological–clinical modified Faine score, parts A and B (MF A + B), in patients with suspected leptospirosis in New Caledonia. A monocentric case–control study was conducted in suspect patients for whom a Leptospira polymerase chain reaction (PCR) test was done within the first 7 days of signs onset at the tertiary hospital from January 2018 to January 2019. Cases and control subjects were matched 1:2 in the gender and age categories. Bivariate, and then multivariable, analyses studied the association between the MF A + B score and a positive Leptospira PCR test, adjusted on the variables retained. In all, 35 cases and 70 control subjects matched for age and gender were analyzed. Multivariable analysis by logistic regression found a significant association between an MF A + B score taken from the categories “possible leptospirosis” (score, 20–25) and “presumed leptospirosis” (score, > 26), and the case or control subject status (P < 0.0001). Model performance was high, with an area under the curve value of 99.27%, 93.55% sensitivity, and 96.36% specificity, which classified subjects correctly in 95.35% of cases. Our study suggests using the MF A + B score to identify possible cases of leptospirosis and initiate antibiotic therapy before biological confirmation in New Caledonia. This score should be evaluated in areas where more differential diagnoses exist and where PCR is not widely available.

Dose-response relationships reflect the effects of a substance on organisms, and are widely used in broad research areas, from medicine and physiology, to vector control and pest management in agronomy. Furthermore, reporting on the response of organisms to stressors is an essential component of many public policies (e.g. public health, environment), and assessment of xenobiotic responses is an integral part of the World Health Organization recommendations. Building upon an R script that we previously made available, and considering its popularity, we have now developed a software package in the R environment, BioRssay, to efficiently analyze dose-response relationships. It has more user-friendly functions, more flexibility, and proposes an easy interpretation of the results. The functions in the BioRssay package are built on robust statistical analyses to compare the dose/exposure-response of various bioassays and effectively visualize them in probit-graphs.

Leptospira strains were isolated from freshwater sampled at four sites in Algeria and characterized by whole-genome sequencing and matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS). The cells were spiral-shaped and motile. Phylogenetic and MALDI-TOF MS analyses showed that the strains can be clearly distinguished from the other described species in the genus Leptospir a, therefore representing two novel species of the pathogen subclade P1 and two novel species of the saprophyte subclade S1. The names Leptospira ainlahdjerensis sp. nov. (type strain 201903070T=KIT0297T=CIP111912T), Leptospira ainazelensis sp. nov. (201903071T=KIT0298T=CIP111913T), Leptospira abararensis sp. nov. (201903074T=KIT0299T=CIP111914T) and Leptospira chreensis (201903075T=KIT0300T=CIP111915T) are proposed.

International audience; Leptospirosis is a neglected waterborne zoonosis of growing concern in tropical and low-income regions. Endemic in Southeast Asia, its distribution and environmental factors such as climate controlling its dynamics remain poorly documented. In this paper, we investigate for the first time the current and future leptospirosis burden at a local scale in mainland Southeast Asia. We adjusted machine-learning models on incidence reports from the Thai surveillance system to identify environmental determinants of leptospirosis. The explanatory variables tested in our models included climate, topographic, land cover and soil variables. The model performing the best in cross-validation was used to estimate the current incidence regionally in Thailand, Myanmar, Cambodia, Vietnam and Laos. It then allowed to predict the spatial distribution of leptospirosis future burden from 2021 to 2100 based on an ensemble of CMIP6 climate model projections and 4 Shared Socio-economics Pathways ranging from the most optimistic to the no-climate policy outcomes (SSP1-2.6, SSP2-4.5, SSP3-7.0 and SSP5-8.5). Leptospirosis incidence was best estimated by 10 environmental variables: four landscape-, four rainfall-, two temperature-related variables. Of all tested scenario, the worst-case scenario of climate change (SSP5-8.5) surprisingly appeared as the best-case scenario for the future of leptospirosis since it would induce a significant global decline in disease incidence in Southeast Asia mainly driven by the increasing temperatures. These global patterns are however contrasted regionally with some regions showing increased incidence in the future. Our work highlights climate and the environment as major drivers of leptospirosis incidence in Southeast Asia. Applying our model to regions where leptospirosis is not routinely monitored suggests an overlooked burden in the region. As our model focuses on leptospirosis responses to environmental drivers only, some other factors, such as poverty, lifestyle or behavioral changes, could further influence these estimated future patterns.

The mosquito Aedes aegypti is the major vector of arboviruses like dengue, Zika and chikungunya viruses. Attempts to reduce arboviruses emergence focusing on Ae. aegypti control has proven challenging due to the increase of insecticide resistances. An emerging strategy which consists of releasing Ae. aegypti artificially infected with Wolbachia in natural mosquito populations is currently being developed. The monitoring of Wolbachia-positive Ae. aegypti in the field is performed in order to ensure the program effectiveness. Here, the reliability of the Matrix‑Assisted Laser Desorption Ionization‑Time Of Flight (MALDI‑TOF) coupled with the machine learning methods like Convolutional Neural Network (CNN) to detect Wolbachia in field Ae. aegypti was assessed for the first time. For this purpose, laboratory reared and field Ae. aegypti were analyzed. The results showed that the CNN recognized Ae. aegypti spectral patterns associated with Wolbachia-infection. The MALDI-TOF coupled with the CNN (sensitivity = 93%, specificity = 99%, accuracy = 97%) was more efficient than the loop-mediated isothermal amplification (LAMP), and as efficient as qPCR for Wolbachia detection. It therefore represents an interesting method to evaluate the prevalence of Wolbachia in field Ae. aegypti mosquitoes.

Background Hemotropic mycoplasmas, previously classified in the genus Eperythrozoon, have been reported as causing human infections in Brazil, China, Japan, and Spain. Methods In 2017, we detected DNA from Candidatus Mycoplasma haemohominis in the blood of a Melanesian patient from New Caledonia presenting with febrile splenomegaly, weight loss, life-threatening autoimmune hemolytic anemia, and hemophagocytosis. The full genome of the bacterium was sequenced from a blood isolate. Subsequently, we retrospectively (2011–2017) and prospectively (2018–2019) tested patients who had been hospitalized with a similar clinico-biological picture. In addition, as these patients had been in contact with frugivorous bats (authorized under conditions for hunting and eating in New Caledonia), we investigated the role of these animals and their biting flies by testing them for hemotropic mycoplasmas. Results There were 15 patients found to be infected by this hemotropic mycoplasma. Among them, 4 (27%) died following splenectomy performed either for spontaneous spleen rupture or to cure refractory autoimmune hemolytic anemia. The bacterium was cultivated from the patient’s blood. The full genome of the Neocaledonian Candidatus M. haemohominis strain differed from that of a recently identified Japanese strain. Of 40 tested Pteropus bats, 40% were positive; 100% of collected bat flies Cyclopodia horsfieldi (Nycteribiidae, Diptera) were positive. Human, bat, and dipteran strains were highly similar. Conclusions The bacterium being widely distributed in bats, Candidatus M. haemohominis, should be regarded as a potential cause of severe infections in humans.

Collective transmission via structures containing several virions has recently emerged as a highly efficient mode of viral spread. Here, we demonstrate that HIV-1 spreads between T lymphocytes in the form of viral particles colonies that are concentrated and sheltered in an extracellular matrix (ECM) lattice enabling their collective transmission upon cell contacts. Intrinsically, ECM-clustered viruses infect T lymphocytes more efficiently than individual viral particles. They preserve HIV-1 transmission from antiretroviral treatment (ArT) and potent broadly neutralizing antibodies. We also show that collagen induced by HIV-1 infection controls the clustering of virions and their collective spread, thereby enhancing infectivity. CD4+ T cells from HIV-1-infected patients produce and transmit ECM-virus clusters, supporting that they could be involved in vivo. This study provides new insights into modes of HIV-1 transmission and identifies a novel fundamental role for collagen in this process. HIV-1 spread via ECM-virus clusters may have important implications for viral dissemination and persistence, including during therapy.

International audience; Gout is the most frequent form of inflammatory arthritis in the world. Its prevalence is particularly elevated in specific geographical areas such as in the Oceania/Pacific region and is rising in the US, Europe, and Asia. Gout is a severe and painful disease, in which co-morbidities are responsible for a significant reduction in life expectancy. However, gout patients remain ostracized because the disease is still considered “self-inflicted”, as a result of unhealthy lifestyle and excessive food and alcohol intake. While the etiology of gout flares is clearly associated with the presence of monosodium urate (MSU) crystal deposits, several major questions remain unanswered, such as the relationships between diet, hyperuricemia and gout flares or the mechanisms by which urate induces inflammation. Recent advances have identified gene variants associated with gout incidence. Nevertheless, genetic origins of gout combined to diet-related possible uric acid overproduction account for the symptoms in only a minor portion of patients. Hence, additional factors must be at play. Here, we review the impact of epigenetic mechanisms in which nutrients (such as ω-3 polyunsaturated fatty acids) and/or dietary-derived metabolites (like urate) trigger anti/pro-inflammatory responses that may participate in gout pathogenesis and severity. We propose that simple dietary regimens may be beneficial to complement therapeutic management or contribute to the prevention of flares in gout patients.

International audience; ObjectiveCarbapenemase-producing Enterobacteriaceae (CRE) and Enterococcus faecium resistant to vancomycin (VRE) constitute major threats to public health worldwide. The Pacific area is concerned and has implemented strategies to control antimicrobial resistance (AMR). However, accurate epidemiological data are rarely reported. Our study aimed to present the strategies applied to prevent and control the spread of highly resistant bacteria in the Pacific territory of New Caledonia.Patients and methodsCohort prospective study of all cases of highly resistant bacteria (HRB) isolated in New Caledonia from September 2004 to December 2020. Evaluation of the impact of the infection control measures implemented in healthcare settings: screening strategy, cohorting unit, IT tools and control of antibiotic prescriptions.ResultsA total of 346 patients with HRB were identified. Most of them (63.0%) were infected or colonized by VRE (n = 218) and 128 by CRE. While the number of CREs significantly increased from 2013 to 2020 (P < 0.0001), control procedures have limited their dissemination. Most patients were colonized by IMP-4-CRE (n = 124/128). The incidence density of VRE significantly decreased from 38.52 for 100,000 hospitalisation-days in 2015 to 4.19 for 100,000 hospitalisation-days in 2019 due to systematic screening of patients before sanitary repatriation from Australia and cohorting implementation. The risk of VRE diffusion is now well under control.ConclusionsOur study confirms that it is possible to control the spread of AMR in a circumscribed territory by means of a global control strategy involving screening, cohorting unit, IT tools and antibiotic prescription controls.

BACKGROUND Pyrethroid insecticides such as deltamethrin have been massively used against Aedes aegypti leading to the spread of resistance alleles worldwide. In an insecticide resistance management context, we evaluated the temporal dynamics of deltamethrin resistance using two distinct populations carrying resistant alleles at different frequencies. Three different scenarios were followed: a continuous selection, a full release of selection, or a repeated introgression with susceptible individuals. The responses of each population to these selection regimes were measured across five generations by bioassays and by monitoring the frequency of knockdown resistance (kdr) mutations and the transcription levels and copy number variations of key detoxification enzymes. RESULTS Knockdown resistance mutations, overexpression and copy number variations of detoxification enzymes as a mechanism of metabolic resistance to deltamethrin was found and maintained under selection across generations. On comparison, the release of insecticide pressure for five generations did not affect resistance levels and resistance marker frequencies. However, introgressing susceptible alleles drastically reduced deltamethrin resistance in only three generations. CONCLUSION The present study confirmed that strategies consisting to stop deltamethrin spraying are likely to fail when the frequencies of resistant alleles are too high and the fitness cost associated to resistance is low. In dead-end situations like in French Guiana where alternative insecticides are not available, alternative control strategies may provide a high benefit for vector control, particularly if they favor the introgression of susceptible alleles in natural populations. © 2021 Society of Chemical Industry.

International audience; Bacterial zoonotic diseases such as leptospirosis, Q fever, melioidosis, spotted fever group rickettsioses, and brucellosis are increasingly recognized causes of non-malaria acute fevers. However, though readily treatable with antibiotics, these diseases are commonly misdiagnosed resulting in poor outcomes in patients. There is a considerable deficit in the understanding of basic aspects of the epidemiology of these neglected diseases and diagnostic tests for these zoonotic bacterial pathogens are not always available in resource-poor settings. Raising awareness about these emerging bacterial zoonoses is directly beneficial to the patients by allowing a test-and-treat approach and is essential to control these life-threatening diseases.

International audience; Dengue virus (DENV) evolutionary dynamics are characterized by frequent DENV genotype/lineage replacements, potentially associated with changes in disease severity and human immunity. New Caledonia (NC) and Cambodia, two contrasted epidemiological settings, respectively experienced a DENV-1 genotype IV to I replacement in 2012 and a DENV-1 genotype I lineage 3 to 4 replacement in 2005-2007, both followed by a massive dengue outbreak. However, their underlying evolutionary drivers have not been elucidated. Here, we tested the hypothesis that these genotype/lineage switches reflected a higher transmission fitness of the replacing DENV genotype/lineage in the mosquito vector using in vivo competition experiments. For this purpose, field-derived Aedes aegypti from NC and Cambodia were orally challenged with epidemiologically relevant pairs of four DENV-1 genotype I and IV strains from NC or four DENV-1 genotype I lineage 3 and 4 strains from Cambodia, respectively. The relative transmission fitness of each DENV-1 genotype/lineage was measured by quantitative RT-PCR for infection, dissemination, and transmission rates. Results showed a clear transmission fitness advantage of the replacing DENV-1 genotype I from NC within the vector. A similar but more subtle pattern was observed for the DENV-1 lineage 4 replacement in Cambodia. Our results support the hypothesis that vector-driven selection contributed to the DENV-1 genotype/lineage replacements in these two contrasted epidemiological settings, and reinforce the idea that natural selection taking place within the mosquito vector plays an important role in DENV short-term evolutionary dynamics.

International audience; Zika virus, an arbovirus responsible for major outbreaks, can cause serious health issues, such as neurological diseases. In the present study, different types of samples (serum, saliva, and urine), collected in 2015–2016 in New Caledonia and French Guiana from 53 patients presenting symptoms and clinical signs triggered by arbovirus infections, were analyzed using a recently developed, and in-house validated, 4-plex RT-qPCR TaqMan method for simultaneous detection and discrimination of the Zika and Chikungunya viruses. Subsequently, statistical analyses were performed in order to potentially establish recommendations regarding the choice of samples type to use for an efficient and early stage Zika infection diagnosis. On this basis, the use of only urine samples presented the highest probability to detect viral RNA from Zika virus. Moreover, such a probability was improved using both urine and saliva samples. Consequently, the added value of non-invasive samples, associated with a higher acceptance level for collection among patients, instead of serum samples, for the detection of Zika infections was illustrated.

International audience; Zika virus (ZIKV) is a Flavivirus transmitted by Aedes mosquitoes, and was responsible for a worldwide outbreak between 2013 and 2016. However, no ZIKV outbreak has been described in Southeast Asia since 2017. In this study, we report the first microcephaly case with probable ZIKV infection during pregnancy in Lao People's Democratic Republic.

Since the epidemic in 2007, studies on vector competence for Zika virus (ZIKV) have intensified, showing that the transmission efficiency varies depending on the vector population, ZIKV strain, and dose of the infectious blood meal. In this study, we aimed to investigate the replication of African and Asian ZIKV strains in vitro and in vivo in order to reveal their phenotypic differences. In addition, we investigated the vector competence of Cambodian Aedes aegypti (Ae. aegypti) mosquitoes (urban and rural) for these ZIKV strains. We observed a significantly higher pathogenicity of the African ZIKV strain in vitro (in mosquito and mammalian cells), and in vivo in both Ae. aegypti and mice. Both mosquito populations were competent to transmit ZIKV as early as 7 days p.i., depending on the population and the ZIKV strain. Ae. aegypti from rural habitats showed significant higher transmission and survival rates than those from urban. We observed the highest transmission efficiency for the African ZIKV isolate (93.3% 14 days p.i.) and for the Cambodian ZIKV isolate (80% 14 days p.i.). Overall, our results highlight the phenotypic differences of the ZIKV lineages and the potential risk of ZIKV transmission by Ae. aegypti mosquitoes. Further investigations of Cambodian mosquito species and ZIKV specific surveillance in humans is necessary in order to improve the local risk assessment.

Background In 2017, New Caledonia experienced an outbreak of severe dengue causing high hospital burden (4379 cases, 416 hospital admissions, 15 deaths). We decided to build a local operational model predictive of dengue severity, which was needed to ease the healthcare circuit. Methods We retrospectively analyzed clinical and biological parameters associated with severe dengue in the cohort of patients hospitalized at the Territorial Hospital between January and July 2017 with confirmed dengue, in order to elaborate a comprehensive patient’s score. Patients were compared in univariate and multivariate analyses. Predictive models for severity were built using a descending step-wise method. Results Out of 383 included patients, 130 (34%) developed severe dengue and 13 (3.4%) died. Major risk factors identified in univariate analysis were: age, comorbidities, presence of at least one alert sign, platelets count 9/L, prothrombin time 10 N, and previous dengue infection. Severity was not influenced by the infecting dengue serotype nor by previous Zika infection. Two models to predict dengue severity were built according to sex. Best models for females and males had respectively a median Area Under the Curve = 0.80 and 0.88, a sensitivity = 84.5 and 84.5%, a specificity = 78.6 and 95.5%, a positive predictive value = 63.3 and 92.9%, a negative predictive value = 92.8 and 91.3%. Models were secondarily validated on 130 patients hospitalized for dengue in 2018. Conclusion We built robust and efficient models to calculate a bedside score able to predict dengue severity in our setting. We propose the spreadsheet for dengue severity score calculations to health practitioners facing dengue outbreaks of enhanced severity in order to improve patients’ medical management and hospitalization flow.

International audience; Dengue virus (DENV) serotype-2 was detected in the South Pacific region in 2014 for the first time in 15 years. In 2016-2020, DENV-2 re-emerged in French Polynesia, Vanuatu, Wallis and Futuna, and New Caledonia, co-circulating with and later replacing DENV-1. In this context, epidemiological and molecular evolution data are paramount to decipher the diffusion route of this DENV-2 in the South Pacific region. In the current work, the E gene from 23 DENV-2 serum samples collected in Vanuatu, Fiji, Wallis and Futuna, and New Caledonia was sequenced. Both maximum likelihood and Bayesian phylogenetic analyses were performed. While all DENV-2 strains sequenced belong to the Cosmopolitan genotype, phylogenetic analysis suggests at least three different DENV-2 introductions in the South Pacific between 2017 and 2020. Strains retrieved in these Pacific Islands Countries and Territories (PICTs) in 2017-2020 are phylogenetically related, with strong phylogenetic links between strains retrieved from French PICTs. These phylogenetic data substantiate epidemiological data of the DENV-2 diffusion pattern between these countries.

Leptospira (L.) interrogans are invasive bacteria responsible for leptospirosis, a worldwide zoonosis. They possess two periplasmic endoflagellae that allow their motility. L. interrogans are stealth pathogens that escape the innate immune recognition of the NOD-like receptors NOD1/2, and the human Toll-like receptor (TLR)4, which senses peptidoglycan and lipopolysaccharide (LPS), respectively. TLR5 is another receptor of bacterial cell wall components, recognizing flagellin subunits. To study the contribution of TLR5 in the host defense against leptospires, we infected WT and TLR5 deficient mice with pathogenic L. interrogans and tracked the infection by in vivo live imaging of bioluminescent bacteria or by qPCR. We did not identify any protective or inflammatory role of murine TLR5 for controlling pathogenic Leptospira. Likewise, subsequent in vitro experiments showed that infections with different live strains of L. interrogans and L. biflexa did not trigger TLR5 signaling. However, unexpectedly, heat-killed bacteria stimulated human and bovine TLR5, but did not, or barely induced stimulation via murine TLR5. Abolition of TLR5 recognition required extensive boiling time of the bacteria or proteinase K treatment, showing an unusual high stability of the leptospiral flagellins. Interestingly, after using antimicrobial peptides to destabilize live leptospires, we detected TLR5 activity, suggesting that TLR5 could participate in the fight against leptospires in humans or cattle. Using different Leptospira strains with mutations in the flagellin proteins, we further showed that neither FlaA nor Fcp participated in the recognition by TLR5, suggesting a role for the FlaB. FlaB have structural homology to Salmonella FliC, and possess conserved residues important for TLR5 activation, as shown by in silico analyses. Accordingly, we found that leptospires regulate the expression of FlaB mRNA according to the growth phase in vitro, and that infection with L. interrogans in hamsters and in mice downregulated the expression of the FlaB, but not the FlaA subunits. Altogether, in contrast to different bacteria that modify their flagellin sequences to escape TLR5 recognition, our study suggests that the peculiar central localization and stability of the FlaB monomers in the periplasmic endoflagellae, associated with the downregulation of FlaB subunits in hosts, constitute an efficient strategy of leptospires to escape the TLR5 recognition and the induced immune response.

International audience; Experimental infections greatly contribute to further deepen our knowledge of infectious diseases. In the case of leptospirosis, hamsters as well as gerbils and guinea pigs have been used as animal models of acute leptospirosis in studying the pathophysiology of the disease. Here we describe a typical Leptospira infection using golden Syrian hamsters. We will also present techniques we use to study the resulting bacterial burden and gene expression patterns in the host in order to decipher the innate immune response to leptospirosis.

International audience; Medical microbiology has used phenotypical and metabolic criteria to identify bacterial pathogens for decades. However, no such criteria have been applied to identify leptospires at the species level. In the recent years, matrix-assisted laser desorption/ionization time-of-flight (MALDI-ToF) mass spectrometry (MS) has emerged as new tool for the identification of bacterial species in the medical microbiology laboratory. This technology has rapidly gained more and more popularity. Actually, this technique is sensitive and economic, saving both labor and bench costs, but also rapid, significantly reducing turnaround time from isolation to identification. MALDI-ToF MS provides an unprecedented tool for the rapid identification of Leptospira at the species level.

International audience; With over one million cases worldwide annually and a high fatality in symptomatic forms, human leptospirosis is a growing public health concern for the most vulnerable populations, especially in the context of global warming and unplanned urbanization. Although the Asia-Pacific region is particularly affected, accurate epidemiological data are often lacking. We conducted an eleven-year retrospective laboratory-based epidemiological survey of human leptospirosis in New Caledonia. From 2006 to 2016, 904 cases were laboratory-confirmed, including 29 fatalities, corresponding to an average annual incidence of 30.6/100,000 and a case fatality rate of 3.2%. Over the period, there was a major shift from indirect serological diagnosis by MAT to direct diagnosis by real-time PCR, a more specific and sensitive test when performed early in the course of the disease. The systematic implementation of genotyping informed on the variety of the infective strains involved, with a predominance of serogroups Icterohaemorrhagiae and Pyrogenes. The epidemiological pattern showed a marked seasonality with an annual peak in March-April. Interestingly, the seasonal peak in children of school age was significantly earlier and corresponded to school holidays, suggesting that attending school from February on could protect children from environmentborne leptospirosis.

Zika virus (ZIKV) has caused severe epidemics in South America beginning in 2015, following its spread through the Pacific. We comparatively assessed the vector competence of ten populations of Aedes aegypti and Ae. albopictus from Brazil and two of Ae. aegypti and one of Culex quinquefasciatus from New Caledonia to transmit three ZIKV isolates belonging to African, Asian and American lineages. Recently colonized mosquitoes from eight distinct sites from both countries were orally challenged with the same viral load (107 TCID50/mL) and examined after 7, 14 and 21 days. Cx. quinquefasciatus was refractory to infection with all virus strains. In contrast, although competence varied with geographical origin, Brazilian and New Caledonian Ae. aegypti could transmit the three ZIKV lineages, with a strong advantage for the African lineage (the only one reaching saliva one-week after challenge). Brazilian Ae. albopictus populations were less competent than Ae. aegypti populations. Ae. albopictus generally exhibited almost no transmission for Asian and American lineages, but was efficient in transmitting the African ZIKV. Viral surveillance and mosquito control measures must be strengthened to avoid the spread of new ZIKV lineages and minimize the transmission of viruses currently circulating.

Introduction Eosinophilic meningitis is a rare form of meningitis with sequelae or death occurring in approximately 2–3% of cases. The most frequent etiological agent is the parasite Angiostrongylus cantonensis. The aim of this study was to characterize New Caledonian cases and to assess the extent to which of A. cantonensis was involved. Material and methods We performed a retrospective study of all cases of eosinophilic meningitis (EM) admitted to the Territorial Hospital of New Caledonia, from 2004 to 2019. We performed a descriptive and a multivariate analysis to identify association of variables with severe and fatal cases (or cases with sequelae). Conclusion Angiostrongyliasis was confirmed as being responsible for 17 of the 92 reported EM cases in New Caledonia from 2004 to 2019 with most being young adults and non-walking infants, and with two peaks of incidence one during the dry season and one during the rainy season. Considering the high incidence and regularity of cases, the potential reservoirs should be identified to target prevention campaigns.

International audience; The genus Uranotaenia (Diptera: Culicidae) has been well documented in Madagascar where it includes 73 species, 89.4% being endemic. However, one problem is that most species are morphologically similar in the adult stage. Here, 713 Uranotaenia specimens collected in the tropical forests of Anorana and Maromizaha between 2008 and 2014 were examined. Using the dichotomous keys for the Uranotaenia fauna of Madagascar published in 2004, three species were identified: Uranotaenia neireti (220), Ur. alboabdominalis (110) and Ur. mayottensis (28). The other specimens (355) were not identifiable and were classified as Uranotaenia sp1. Using wing morphometry, the four taxa were classified into four morphogroups. Within the Uranotaenia sp1 group, specimens from the Anorana forest and those from the Maromizaha forest overlapped. This result suggests that wing morphometric traits could be a good marker to distinguish Uranotaenia species in Madagascar.