Borréliose de Lyme : de l’exposition aux formes graves en France : quelles données pour appréhender l’épidémiologie de la Borréliose de Lyme en France ?

Lyne Borreliosis (LB) is the most common vector-borne infectious disease in France. Specific knowledge about the risk of transmission to humans of agents carried by ticks are still needed. Epidemiological data at each stage of the infection cycle (tick exposure, tick bites, infection, disease...) are needed to accurately estimate its incidence, assess trends, identify geographical areas and at risk populations and guide the prioritization of public health resources for LB prevention and control.The aim of this thesis will be to quantify the exposure to tick bites and tick-borne pathogens and to evaluate the validity of the PMSI as surveillance system for hospitalized LB cases.A third of the population residing in metropolitan France stated that they had already been bitten by a tick during their lifetime and a quarter felt exposed to tick bites In rural and high incidence areas of BL, these proportions were higher.. An increase knowledge and application of preventive measures was observed between 2016 and 2019. High Borrelia burgdorferi sl seroprevalence among forestry workers of the northern half of France, particularly in the east, has been estimated. Data from PMSI have been shown to be useful for surveillance of disseminated LB cases.This thesis work bring new knowledge for operational purposes in public health, or to deepen it, on the epidemiology of Lyme borreliosis in France.La borréliose de Lyme (BL) est la plus fréquente des maladies à transmission vectorielle en France. Le besoin de connaissances précises sur le risque de transmission à l’homme des agents transportés par les tiques soulève toujours de nombreuses questions. Des données épidémiologiques à chaque étape du cycle de l’infection (exposition aux tiques, piqures, infection, maladie clinique…) sont nécessaires pour estimer précisément son incidence, évaluer les tendances, identifier les zones géographiques et les populations à risque et orienter la priorisation des ressources de santé publique pour la prévention et le contrôle de la BL. L’objectif de cette thèse est de quantifier l’exposition aux piqures de tiques, et aux agents pathogènes transmis par des tiques et d’évaluer la validité du système de surveillance des cas hospitalisés pour la borréliose de Lyme.Près d’un tiers de la population résidant en France métropolitaine déclarait avoir déjà été piquée par une tique au cours de la vie et un quart se sentait exposé aux piqûres de tiques. Dans les zones rurales et de haute incidence de la BL, ces proportions étaient plus élevées. Une augmentation des connaissances et de l’application des mesures de prévention a été observée entre 2016 et 2019. Une séroprévalence à Borrelia burgdorferi sl importante parmi les travailleurs forestiers de la moitié nord de la France, notamment dans l’Est, a été estimée. Les données issues du PMSI, ont été montrées comme utile pour la surveillance des cas BL présentant des formes disséminéesCe travail de thèse a permis d’amener des connaissances nouvelles à visée opérationnelle en santé publique, ou de les approfondir, sur l’épidémiologie de la Borréliose de Lyme en France

Lyme Borreliosis : from exposure to severe clinical manifestations

La borréliose de Lyme (BL) est la plus fréquente des maladies à transmission vectorielle en France. Le besoin de connaissances précises sur le risque de transmission à l’homme des agents transportés par les tiques soulève toujours de nombreuses questions. Des données épidémiologiques à chaque étape du cycle de l’infection (exposition aux tiques, piqures, infection, maladie clinique…) sont nécessaires pour estimer précisément son incidence, évaluer les tendances, identifier les zones géographiques et les populations à risque et orienter la priorisation des ressources de santé publique pour la prévention et le contrôle de la BL. L’objectif de cette thèse est de quantifier l’exposition aux piqures de tiques, et aux agents pathogènes transmis par des tiques et d’évaluer la validité du système de surveillance des cas hospitalisés pour la borréliose de Lyme.Près d’un tiers de la population résidant en France métropolitaine déclarait avoir déjà été piquée par une tique au cours de la vie et un quart se sentait exposé aux piqûres de tiques. Dans les zones rurales et de haute incidence de la BL, ces proportions étaient plus élevées. Une augmentation des connaissances et de l’application des mesures de prévention a été observée entre 2016 et 2019. Une séroprévalence à Borrelia burgdorferi sl importante parmi les travailleurs forestiers de la moitié nord de la France, notamment dans l’Est, a été estimée. Les données issues du PMSI, ont été montrées comme utile pour la surveillance des cas BL présentant des formes disséminéesCe travail de thèse a permis d’amener des connaissances nouvelles à visée opérationnelle en santé publique, ou de les approfondir, sur l’épidémiologie de la Borréliose de Lyme en France.Lyne Borreliosis (LB) is the most common vector-borne infectious disease in France. Specific knowledge about the risk of transmission to humans of agents carried by ticks are still needed. Epidemiological data at each stage of the infection cycle (tick exposure, tick bites, infection, disease...) are needed to accurately estimate its incidence, assess trends, identify geographical areas and at risk populations and guide the prioritization of public health resources for LB prevention and control.The aim of this thesis will be to quantify the exposure to tick bites and tick-borne pathogens and to evaluate the validity of the PMSI as surveillance system for hospitalized LB cases.A third of the population residing in metropolitan France stated that they had already been bitten by a tick during their lifetime and a quarter felt exposed to tick bites In rural and high incidence areas of BL, these proportions were higher.. An increase knowledge and application of preventive measures was observed between 2016 and 2019. High Borrelia burgdorferi sl seroprevalence among forestry workers of the northern half of France, particularly in the east, has been estimated. Data from PMSI have been shown to be useful for surveillance of disseminated LB cases.This thesis work bring new knowledge for operational purposes in public health, or to deepen it, on the epidemiology of Lyme borreliosis in France

Exploratory Space–Time Analyses of Reported Lyme Borreliosis Cases in France, 2016–2019

International audienceIn recent decades, the incidence of Lyme borreliosis (LB) in Europe seems to have increased, underpinning a growing public health concern. LB surveillance systems across the continent are heterogeneous, and the spatial and temporal patterns of LB reports have been little documented. In this study, we explored the spatio-temporal patterns of LB cases reported in France from 2016 to 2019, to describe high-risk clusters and generate hypotheses on their occurrence. The space-time K-function and the Kulldorf's scan statistic were implemented separately for each year to evaluate space-time interaction between reported cases and searching clusters. The results show that the main spatial clusters, of radius size up to 97 km, were reported in central and northeastern France each year. In 2017-2019, spatial clusters were also identified in more southern areas (near the Alps and the Mediterranean coast). Spatio-temporal clustering occurred between May and August, over one-month to three-month windows in 2016-2017 and in 2018-2019. A strong spatio-temporal interaction was identified in 2018 within 16 km and seven days, suggesting a potential local and intense pathogen transmission process. Ongoing improved surveillance and accounting for animal hosts, vectors, meteorological factors and human behaviors are keys to further elucidate LB spatio-temporal patterns

Pet rodents as possible risk for leptospirosis, Belgium and France, 2009 to 2016

International audienceLeptospirosis is an under-reported and emerging zoonotic disease which is potentially fatal in humans. Rodents are the main reservoirs for pathogenic Leptospira spp., but diagnosis in these animals is difficult, and their infection, which does not induce symptoms, usually goes unoticed. Although the exposures of most human cases of leptospirosis are poorly documented, we were able to identify six human cases of leptospirosis which were associated with direct contact with pet rodents (mice or rats) in Belgium and France between 2009 and 2016. All cases had severe disease and for all, the presence of Leptospira spp. DNA in the kidneys of their pet animals was confirmed, strongly suggesting that excretion of leptospires in urine was the way of transmission. Half of the cases shared the serogroup Icterohaemorrhagiae, which is usually associated with severe disease, with the pet rats which they were in contact with. With the popularity of rats and mice as pets, this study should contribute to raising awareness on asymptomatic pet rodents as a source of Leptospira infections

Contributions of the qualitative Qualicor study embedded in a cohort study on the circumstances of SARS-CoV 2 infection in France

International audienceObjectivesThis study aims to understand a major result of ComCor, an online epidemiological study conducted to identify the circumstances of COVID-19 infection in France from 2020 to 2022: One third of respondents reported ignoring the circumstances of their infection.MethodsWe conducted a qualitative study through semi-structured interviews, diagnosed in spring or summer 2021. Interviews were audio recorded, transcribed, and thematically analyzed.ResultsFifty interviews were conducted. Half of the participants in Qualicor were able to identify several at-risk situations, most often involving their entourage (family, friends, colleagues), but were uncertain as to which specific situation was the source of infection. Less than one quarter strongly suspected a specific situation without certainty, a similar proportion were unable to identify any circumstances, and only two people were certain about the origin of the infection. Several factors contributed to this lack of knowledge: a desire to conceal these circumstances (in a few rare cases), limitations of the questionnaire, lack of knowledge about how the virus is transmitted, selective perception of at-risk situations, co-existence of several possible sources of infection, and the difficulty of taking an objective view of certain circumstances of transmission.ConclusionOur study shows the benefits of a mixed approach designed to better understand the perception of Covid 19 contamination circumstances in the French population. It also highlights the need to strengthen or improve communication on modes of virus transmission, especially airborne transmission, and the importance of maintaining certain preventive behaviors after vaccination

Spatial and seasonal determinants of Lyme borreliosis incidence in France, 2016 to 2021

International audienceBackground Lyme borreliosis (LB) is the most widespread hard tick-borne zoonosis in the northern hemisphere. Existing studies in Europe have focused mainly on acarological risk assessment, with few investigations exploring human LB occurrence. Aim We explored the determinants of spatial and seasonal LB variations in France from 2016 to 2021 by integrating environmental, animal, meteorological and anthropogenic factors, and then mapped seasonal LB risk predictions. Methods We fitted 2016–19 LB national surveillance data to a two-part spatio-temporal statistical model. Spatial and temporal random effects were specified using a Besag-York-Mollie model and a seasonal model, respectively. Coefficients were estimated in a Bayesian framework using integrated nested Laplace approximation. Data from 2020–21 were used for model validation. Results A high vegetation index (≥ 0.6) was positively associated with seasonal LB presence, while the index of deer presence (> 60%), mild soil temperature (15–22 °C), moderate air saturation deficit (1.5–5 mmHg) and higher tick bite frequency were associated with increased incidence. Prediction maps show a higher risk of LB in spring and summer (April–September), with higher incidence in parts of eastern, midwestern and south-western France. Conclusion We present a national level spatial assessment of seasonal LB occurrence in Europe, disentangling factors associated with the presence and increased incidence of LB. Our findings yield quantitative evidence for national public health agencies to plan targeted prevention campaigns to reduce LB burden, enhance surveillance and identify further data needs. This approach can be tested in other LB endemic areas

Seroprevalence of Hantavirus in Forestry Workers, Northern France, 2019–2020

We aimed to estimate the seroprevalence of Puumala orthohantavirus (PUUV) among forestry workers in northern France, and to explore sociodemographic risk factors. We conducted a random cross-sectional seroprevalence survey among 1777 forestry workers in 2019–2020. The presence of immunoglobulin G against PUUV antigens in serum was assessed using enzyme-linked immunosorbent assay and confirmed using immunofluorescence assay. Poisson regression models were used to explore factors associated with seropositivity. Weighted seroprevalence was 5% (3–6) in northeastern France, 4% (2–6) in north central France, and 1% in two regions located in the center of the country (Auvergne and Limousin). There were no seropositive workers detected in northwestern France. Seropositivity was associated with age, sex, and cumulative seniority in the forestry sector. Seroprevalence was highest in known endemic areas of the northeast and lowest in the northwest. Nevertheless, we found serological evidence of PUUV infection in two regions located in the center of the country, suggesting circulation of the virus in these regions, previously thought to be non-endemic

Imported chikungunya cases in an area newly colonised by Aedes albopictus : mathematical assessment of the best public health strategy

International audienceWe aimed to identify the optimal strategy that should be used by public health authorities against transmission of chikungunya virus in mainland France. The theoretical model we developed, which mimics the current surveillance system, predicted that without vector control (VC), the probability of local transmission after introduction of viraemic patients was around 2%, and the number of autochthonous cases between five and 15 persons per hectare, depending on the number of imported cases. Compared with this baseline, we considered different strategies (VC after clinical suspicion of a case or after laboratory confirmation, for imported or autochthonous cases): Awaiting laboratory confirmation for suspected imported cases to implement VC had no significant impact on the epidemiological outcomes analysed, mainly because of the delay before entering into the surveillance system. However, waiting for laboratory confirmation of autochthonous cases before implementing VC resulted in more frequent outbreaks. After analysing the economic cost of such strategies, our study suggested implementing VC immediately after the notification of a suspected autochthonous case as the most efficient strategy in settings where local transmission has been proven. Nevertheless, we identified that decreasing reporting time for imported cases should remain a priority

Prevalence and factors associated with a prescription of a Lyme borreliosis serology for erythema migrans diagnosis in general practice: a study from the French sentinel network, 2009–2020

Abstract Background Serological testing of patients consulting for typical erythema migrans (EM) is not recommended in European recommendations for diagnosis of Lyme borreliosis (LB). Little is known on the level of adherence of French general practitioners to these recommendations. The objectives were to estimate the proportion of Lyme borreliosis serological test prescription in patients with erythema migrans seen in general practice consultations in France, and to study the factors associated with this prescription. Methods LB cases with an EM reported by the French general practitioners (GPs) of the Sentinelles network between January 2009 and December 2020 were included. To assess the associations with a prescription of a serological test, multilevel logistic regression models were used. Results Among the 1,831 EM cases included, a prescription for a LB serological test was requested in 24.0% of cases. This proportion decreased significantly over the study period, from 46.8% in 2009 to 15.8% in 2020. A LB serological prescription was associated with patients with no reported tick bite (Odds Ratio (OR): 1.95; 95% confidence interval [1.23–3.09]), multiple EM (OR: 3.82 [1.63–8.92]), EM of five centimeters or more (OR: 4.34 [2.33–8.08]), and GPs having diagnosed less than one EM case per year during the study period (OR: 5.28 [1.73–16.11]). Conclusions Serological testing of patients consulting for EM is not recommended in European recommendations for diagnosis of Lyme borreliosis. Therefore, the significant decrease in the rate of LB serological test for EM over the study period is encouraging. The factors identified in this study can be used to improve messaging to GPs and patients. Further efforts are needed to continue to disseminate diagnostic recommendations for LB to GPs, especially those who rarely see patients with EM

Mortality from malaria in France, 2005 to 2014

International audienceIntroduction Malaria is a notifiable disease in all European Union and European Economic Area countries except Belgium and France, where only autochthonous malaria is notifiable. Although morbidity caused by malaria has been assessed, little is known about mortality incidence. Objective Our aim was to estimate the number of imported malaria-related deaths in hospital in metropolitan France.Methods We matched individual deaths reported between 1 January 2005 and 31 December 2014 to the French National Reference Centre for malaria (FNRCm) with malaria-related deaths from two other sources: the French National Registry on medical causes of death and the French national hospital discharge database. A capture–recapture method with log-linear modelling was used. Age, sex and place of death stratification were applied to remove heterogeneity.Results The estimated malaria-related deaths in metropolitan France during the study period were 205 (95% confidence interval (CI): 191–219). The annual mean number of malaria-related deaths was estimated at 21 (95% CI: 19–22). The FNRCm malaria-related deaths surveillance had a 38% sensitivity (95% CI: 32–44). Among 161 in-hospital individual malaria-related deaths reported from three data sources, the sex ratio (male to female) was 2.6. Median age of the patients was 57 years, ranging from 1 to 89 years.Conclusion The pertinent finding of this report is that malaria-related death records were significantly less* complete than case records. Therefore, data comparison of imported malaria morbidity and mortality between countries should imperatively be assessed using standard indicators weighted according to the completeness of health surveillance systems