Influence of Vectors' Risk-Spreading Strategies and Environmental Stochasticity on the Epidemiology and Evolution of Vector-Borne Diseases: The Example of Chagas' Disease

Insects are known to display strategies that spread the risk of encountering unfavorable conditions, thereby decreasing the extinction probability of genetic lineages in unpredictable environments. To what extent these strategies influence the epidemiology and evolution of vector-borne diseases in stochastic environments is largely unknown. In triatomines, the vectors of the parasite Trypanosoma cruzi, the etiological agent of Chagas' disease, juvenile development time varies between individuals and such variation most likely decreases the extinction risk of vector populations in stochastic environments. We developed a simplified multi-stage vector-borne SI epidemiological model to investigate how vector risk-spreading strategies and environmental stochasticity influence the prevalence and evolution of a parasite. This model is based on available knowledge on triatomine biodemography, but its conceptual outcomes apply, to a certain extent, to other vector-borne diseases. Model comparisons between deterministic and stochastic settings led to the conclusion that environmental stochasticity, vector risk-spreading strategies (in particular an increase in the length and variability of development time) and their interaction have drastic consequences on vector population dynamics, disease prevalence, and the relative short-term evolution of parasite virulence. Our work shows that stochastic environments and associated risk-spreading strategies can increase the prevalence of vector-borne diseases and favor the invasion of more virulent parasite strains on relatively short evolutionary timescales. This study raises new questions and challenges in a context of increasingly unpredictable environmental variations as a result of global climate change and human interventions such as habitat destruction or vector control.Centro de Estudios Parasitológicos y de Vectore

Influence of Vectors' Risk-Spreading Strategies and Environmental Stochasticity on the Epidemiology and Evolution of Vector-Borne Diseases: The Example of Chagas' Disease

Insects are known to display strategies that spread the risk of encountering unfavorable conditions, thereby decreasing the extinction probability of genetic lineages in unpredictable environments. To what extent these strategies influence the epidemiology and evolution of vector-borne diseases in stochastic environments is largely unknown. In triatomines, the vectors of the parasite Trypanosoma cruzi, the etiological agent of Chagas' disease, juvenile development time varies between individuals and such variation most likely decreases the extinction risk of vector populations in stochastic environments. We developed a simplified multi-stage vector-borne SI epidemiological model to investigate how vector risk-spreading strategies and environmental stochasticity influence the prevalence and evolution of a parasite. This model is based on available knowledge on triatomine biodemography, but its conceptual outcomes apply, to a certain extent, to other vector-borne diseases. Model comparisons between deterministic and stochastic settings led to the conclusion that environmental stochasticity, vector risk-spreading strategies (in particular an increase in the length and variability of development time) and their interaction have drastic consequences on vector population dynamics, disease prevalence, and the relative short-term evolution of parasite virulence. Our work shows that stochastic environments and associated risk-spreading strategies can increase the prevalence of vector-borne diseases and favor the invasion of more virulent parasite strains on relatively short evolutionary timescales. This study raises new questions and challenges in a context of increasingly unpredictable environmental variations as a result of global climate change and human interventions such as habitat destruction or vector control.Centro de Estudios Parasitológicos y de Vectore

Adaptive developmental delay in chagas disease vectors: an evolutionary ecology approach

The developmental time of vector insects is important to their population dynamics, evolutionary biology, epidemiology of the diseases they transmit, and to their responses to global climatic change. In various triatomine species vectors of Chagas disease (Triatominae, Reduviidae), a delay in the molt of a small proportion of individuals has been observed, and from an evolutionary ecology approach, we propose the hypothesis that the developmental delay is an adaptation to environmental stochasticity through a spreading of risk (bet-hedging) diapause strategy. We confirmed, by means of a survey among specialists, the existence of the developmental delay in triatomines. Statistical descriptions of the developmental time of 11 species of triatomines showed some degree of bi-modality in nine of them. We predicted by means of an optimization model which genotype, coding for a given frequency of developmental diapause, is expected to evolve. We identified a series of parameters that can be measured in the field and in the laboratory to test the hypothesis of an optimal diapause frequency. We also discuss the importance of these findings for triatomines in terms of global climatic change and epidemiological consequences such as their resistance to insecticides.Facultad de Ciencias Naturales y Muse

Influence of Vectors' Risk-Spreading Strategies and Environmental Stochasticity on the Epidemiology and Evolution of Vector-Borne Diseases: The Example of Chagas' Disease

Insects are known to display strategies that spread the risk of encountering unfavorable conditions, thereby decreasing the extinction probability of genetic lineages in unpredictable environments. To what extent these strategies influence the epidemiology and evolution of vector-borne diseases in stochastic environments is largely unknown. In triatomines, the vectors of the parasite Trypanosoma cruzi, the etiological agent of Chagas' disease, juvenile development time varies between individuals and such variation most likely decreases the extinction risk of vector populations in stochastic environments. We developed a simplified multi-stage vector-borne SI epidemiological model to investigate how vector risk-spreading strategies and environmental stochasticity influence the prevalence and evolution of a parasite. This model is based on available knowledge on triatomine biodemography, but its conceptual outcomes apply, to a certain extent, to other vector-borne diseases. Model comparisons between deterministic and stochastic settings led to the conclusion that environmental stochasticity, vector risk-spreading strategies (in particular an increase in the length and variability of development time) and their interaction have drastic consequences on vector population dynamics, disease prevalence, and the relative short-term evolution of parasite virulence. Our work shows that stochastic environments and associated risk-spreading strategies can increase the prevalence of vector-borne diseases and favor the invasion of more virulent parasite strains on relatively short evolutionary timescales. This study raises new questions and challenges in a context of increasingly unpredictable environmental variations as a result of global climate change and human interventions such as habitat destruction or vector control.Centro de Estudios Parasitológicos y de Vectore

Adaptive Developmental Delay in Chagas Disease Vectors: An Evolutionary Ecology Approach

The developmental time of vector insects is important to their population dynamics, evolutionary biology, epidemiology of the diseases they transmit, and to their responses to global climatic change. In various triatomine species vectors of Chagas disease (Triatominae, Reduviidae), a delay in the molt of a small proportion of individuals has been observed, and from an evolutionary ecology approach, we propose the hypothesis that the developmental delay is an adaptation to environmental stochasticity through a spreading of risk (bet-hedging) diapause strategy. We confirmed, by means of a survey among specialists, the existence of the developmental delay in triatomines. Statistical descriptions of the developmental time of 11 species of triatomines showed some degree of bi-modality in nine of them. We predicted by means of an optimization model which genotype, coding for a given frequency of developmental diapause, is expected to evolve. We identified a series of parameters that can be measured in the field and in the laboratory to test the hypothesis of an optimal diapause frequency. We also discuss the importance of these findings for triatomines in terms of global climatic change and epidemiological consequences such as their resistance to insecticides

Long-Term Inhaled Corticosteroid Adherence in Asthma Patients with Short-Term Adherence

International audienceBACKGROUND: Although the use of inhaled corticosteroids (ICS) in asthma is known to be overall erratic, the long-term use of ICS by patients selected during an episode of regular use is poorly documented. OBJECTIVE: In a cohort of patients with asthma regularly acquiring ICS therapy over several months, we verified whether these patients remained treated in the following 12 months. The correlates of regular ICS use over this period were investigated. METHODS: A historical cohort of patients with asthma was identified from the Echantillon généraliste de bénéficiaires national French health care reimbursement data (2007-2012). Patients (6-40 years) were selected during a regular ICS use episode, with 3 or more ICS refills within 120 days. Continuous multiple-interval measures of medication availability (CMA) were computed for the 12 months after the third dispensation, and the factors associated with a CMA value of 80% or more (adherent patients) were identified. RESULTS: Among 5096 patients (42.1% children/teenagers, 48.8% females), only 24.0% had a CMA value of 80% or more (mean CMA = 54.4%) over the 12 months following the ICS selection period. Achieving a CMA value of 80% or more was primarily associated with being a child/teenager (P = .002), having more severe or less controlled asthma (P = .007), more previous dispensing of short-acting beta agonists (P \\textless .0001), and receiving devices with 200 unit doses (P \\textless .0001). Adherent patients had more frequent general practitioner visits (P \\textless .0001), more distinct prescribers of respiratory therapy (P = .0002), and more frequent switches of ICS (P \\textless .0001). CONCLUSIONS: Most patients with asthma selected during an episode of regular ICS use did not maintain therapy over the following months. Adherence should be repeatedly monitored, and the reasons for discontinuation should be investigated, at prescriber and patient levels

Influence of vectors' risk-spreading strategies and environmental stochasticity on the epidemiology and evolution of vector-borne diseases: the example of Chagas' disease.

Insects are known to display strategies that spread the risk of encountering unfavorable conditions, thereby decreasing the extinction probability of genetic lineages in unpredictable environments. To what extent these strategies influence the epidemiology and evolution of vector-borne diseases in stochastic environments is largely unknown. In triatomines, the vectors of the parasite Trypanosoma cruzi, the etiological agent of Chagas' disease, juvenile development time varies between individuals and such variation most likely decreases the extinction risk of vector populations in stochastic environments. We developed a simplified multi-stage vector-borne SI epidemiological model to investigate how vector risk-spreading strategies and environmental stochasticity influence the prevalence and evolution of a parasite. This model is based on available knowledge on triatomine biodemography, but its conceptual outcomes apply, to a certain extent, to other vector-borne diseases. Model comparisons between deterministic and stochastic settings led to the conclusion that environmental stochasticity, vector risk-spreading strategies (in particular an increase in the length and variability of development time) and their interaction have drastic consequences on vector population dynamics, disease prevalence, and the relative short-term evolution of parasite virulence. Our work shows that stochastic environments and associated risk-spreading strategies can increase the prevalence of vector-borne diseases and favor the invasion of more virulent parasite strains on relatively short evolutionary timescales. This study raises new questions and challenges in a context of increasingly unpredictable environmental variations as a result of global climate change and human interventions such as habitat destruction or vector control

Frequency of comorbidities in chronic obstructive pulmonary disease, and impact on all-cause mortality: A population-based cohort study

International audienceBACKGROUND: In chronic obstructive pulmonary disease (COPD), the role of specific comorbidities on all-cause mortality is of major interest particularly with a database representative of the beneficiaries covered by the French health system. We investigated the frequency and the role of major comorbidities on all-cause mortality in a population-based cohort of COPD patients, and whether this impact was modulated by gender. METHODS: A historical cohort was identified in the French claims data. Patients aged >=45 years were selected in 2006 from the French national claims data (1/97(th) random sample) by at least one of the following criteria: (a) COPD-related hospitalisations, (b) long-term disease status for COPD, (c) dispensations of bronchodilators. Cardiovascular diseases, diabetes, depression and cancer were defined by specific therapy and/or long-term disease status. The impact of comorbidities on mortality was investigated during a seven-year follow-up period (2007-2013), using Cox models. RESULTS: In 4,237 patients (mean age 68 years, 55% males, mean annual death-rate 4.9%), cardiovascular diseases, diabetes, depression and cancers were identified in 68.7%, 15.2%, 14.2% and 10.6% of patients, respectively. Associations with mortality were significant for cardiovascular diseases (HR = 1.2, 95%CI = [1.0-1.4]), diabetes (HR = 1.2, 95%CI = [1.0-1.4]), depression (HR = 1.4, 95%CI = [1.2-1.6]) and cancers (HR = 1.6, 95%CI = [1.4-1.9]), with no difference between genders. CONCLUSIONS: In the French population, major comorbidities are common in COPD, particularly cardiovascular diseases that occur in over two thirds of patients. The impact of comorbidities on mortality was not related to their prevalence, with cancer having the largest impact