Biology subjects

Delecroix, C.

Publications and source records attributed to Delecroix, C..

5 recordsLinked to original sources

bioRxiv2026

Territorial risk of high pathogenicity avian influenza in France is associated with farmed species diversity

Animal infectious diseases threaten food security, livestock production and public health. While disease prevention strategies typically target risk factors associated with high-competence hosts or environmental conditions, we hypothesise that lower-competence species can reduce disease risk by diluting effective contact rates between farms. Using spatial statistical models calibrated on three successive French high pathogenicity avian influenza (HPAI) epidemics (2020-2023), we show that greater local diversity of livestock farms, including cattle and pig farms, is associated with significantly lower HPAI risk. Moreover, we show that the positive association between duck houses and HPAI risk weakens as the number of less-competent non-duck poultry houses increases, revealing a dilution effect within poultry production systems. These findings suggest that livestock diversity is a previously overlooked determinant of disease spread and open new research avenues on territorial diversification to complement traditional approaches for the long-term control of high-impact animal infectious diseases.

ecology↗

bioRxiv2026

A modelling challenge to improve preparedness for highly pathogenicavian influenza epidemics: objectives, design and synthetic datageneration

Highly pathogenic avian influenza (HPAI) is among the most significant disease threats to poultry worldwide. Modelling challenges, where independent teams address a common epidemiological scenario, can support the development of response capabilities and strengthen communication between modellers and risk managers. Despite the established benefits of these exercises, they remain uncommon in animal health, and none have previously addressed avian influenza. Here Jolly Island, an artificial landscape of 9160 poultry farms with five production types, was developed and seeded with stochastic HPAI epidemics that ran their course over a three-to-four month period. From January through April 2026, 45 registered teams across five continents investigated a selected synthetic epidemic, producing probabilistic forecasts, inferring transmission drivers, and evaluating counterfactual control policies. Here the objectives, design choices, and data generation of the HPAI Modelling Challenge are described in full, covering transmission processes, surveillance system operations, and control strategy implementation, along with the selected epidemic trajectory, the narrative situation reports supplied to the teams at each phase, and the complete phase-specific datasets released to them. As the opening paper of this special issue, here is provided the foundation upon which all subsequent contributions, where teams document their approaches and analyses, are built.

ecology↗

bioRxiv2024

Multivariate resilience indicators to anticipate vector-borne disease outbreaks: a West Nile virus case-study

Background and aimTo prevent the spread of infectious diseases, successful interventions require early detection. The timing of implementation of preventive measures is crucial, but as outbreaks are hard to anticipate, control efforts often start too late. This applies to mosquito-borne diseases, for which the multifaceted nature of transmission complicates surveillance. Resilience indicators have been studied as a generic, model-free early warning method. However, the large data requirements limit their use in practice. In the present study, we compare the performance of multivariate indicators of resilience, combining the information contained in multiple data sources, to the performance of univariate ones focusing on one single time series. Additionally, by comparing various monitoring scenarios, we aim to find which data sources are the most informative as early warnings. Methods and resultsWest Nile virus was used as a case study due to its complex transmission cycle with different hosts and vectors interacting. A synthetic dataset was generated using a compartmental model under different monitoring scenarios, including data-poor scenarios. Multivariate indicators of resilience relied on different data reduction techniques such as principal component analysis (PCA) and Max Autocorrelation Factor analysis (MAF). Multivariate indicators outperformed univariate ones, especially in data-poor scenarios such as reduced resolution or observation probabilities. This finding held across the different monitoring scenarios investigated. In the explored system, species that were more involved in the transmission cycle or preferred by the mosquitoes were not more informative for early warnings. ImplicationsOverall, these results indicate that combining multiple data sources into multivariate indicators can help overcome the challenges of data requirements for resilience indicators. The final decision should be based on whether the additional effort is worth the gain in prediction performance. Future studies should confirm these findings in real-world data and estimate the sensitivity, specificity, and lead time of multivariate resilience indicators. Author summaryVector-borne diseases (VBD) represent a significant proportion of infectious diseases and are expanding their range every year because of among other things climate change and increasing urbanization. Successful interventions against the spread of VBD requires anticipation. Resilience indicators are a generic, model-free approach to anticipate critical transitions including disease outbreaks, however the large data requirements limit their use in practice. Since the transmission of VBD involves several species interacting with one another, which can be monitored as different data sources. The information contained by these different data sources can be combined to calculate multivariate indicators of resilience, allowing a reduction of the data requirements compared to univariate indicators relying solely on one data source. We found that such multivariate indicators outperformed univariate indicators in data-poor contexts. Multivariate indicators could be used to anticipate not only VBD outbreaks but also other transitions in complex systems such as ecosystems collapse or episodes of chronic diseases. Adapting the surveillance programs to collect the relevant data for multivariate indicators of resilience entails new challenges related to costs, logistic ramifications and coordination of different institutions involved in surveillance.

systems biology↗

bioRxiv2023

Mechanistic models for West Nile Virus transmission:A systematic review of features, aims, and parameterisation

Mathematical models within the Ross-Macdonald framework increasingly play a role in our understanding of vector-borne disease dynamics and as tools for assessing scenarios to respond to emerging threats. These threats are typically characterised by a high degree of heterogeneity, introducing a range of possible complexities in models and challenges to maintain the link with empirical evidence. We systematically identified and analysed a total of 67 published papers presenting compartmental West Nile Virus (WNV) models that use parameter values derived from empirical studies. Using a set of fifteen criteria, we measured the dissimilarity compared to the Ross-Macdonald framework. We also retrieved the purpose and type of models and traced the empirical sources of their parameters. Our review highlights the increasing refinements in WNV models. Models for prediction included the highest number of refinements. We found uneven distributions of refinements and of evidence for parameter values. We identified several challenges in parameterising such increasingly complex models. For parameters common to most models, we also synthesise the empirical evidence for their values and ranges. The study highlights the potential to improve the quality of WNV models and their applicability for policy by establishing closer collaboration between mathematical modelling and empirical work.

ecology↗

bioRxiv2023

Monitoring Resilience in Bursts

The possibility to anticipate critical transitions through detecting loss of resilience has attracted attention in a variety of fields. Resilience indicators rely on the mathematical concept of critical slowing down, which means that a system recovers increasingly slowly from external perturbations when approaching a tipping point. This decrease in recovery rate can be reflected in rising autocorrelation and variance in data. To test whether resilience is changing, resilience indicators are often calculated using a moving window in long, continuous time series of the system. However, for some systems it may be more feasible to collect several high-resolution time series in short periods of time, i.e. in bursts. Resilience indicators can then be calculated to detect a change of resilience in a system between such bursts. Here, we compare the performance of both methods using simulated data, and showcase possible use of bursts in a case-study using mood data to anticipate depression in a patient. Using the same number of data points, the burst approach outperformed the moving window method, suggesting that it is possible to down-sample the continuous time series and still signal of an upcoming transition. We suggest guidelines to design an optimal sampling strategy. Our results imply that using bursts of data instead of continuous time series may improve the capacity to detect changes in systems resilience. This method is promising for a variety of fields, such as human health, epidemiology, or ecology, where continuous monitoring is costly or unfeasible. Significance statementGauging the risk of tipping points is of great relevance in complex systems ranging from health to climate, and ecosystems. For this purpose, dynamical indicators of resilience are being derived from long continuous time series to monitor the system and obtain early warning signals. However, gathering such data is often prohibitively expensive or practically unfeasible. Here we show that collecting data in brief, intense bursts may often solve the problem, making it possible to estimate change in resilience between the bursts withrelatively high precision. This may be particularly useful for monitoring resilience of humans or animals, where brief time series of blood pressure, balance, mood or other relevant markers may be collected relatively easily to help estimating systemic resilience.

ecology↗