Epidemiology (EPI) Unit
Head of Unit: Benoit Durand
The Epidemiology (EPI) Unit conducts research and surveillance support activities in the field of animal health.
The unit runs the foot-and-mouth disease rapid-response unit, which conducts permanent monitoring (24/7) via a telephone hotline for the validation of clinical suspicions of foot-and-mouth disease. It participates in the epidemiology activities of the European Union Reference Laboratory for Foot-and-mouth disease. Lastly, the unit collaborates with the other units of the Laboratory for Animal Health in epidemiological investigations of emerging or re-emerging pathogens. This was the case, for example, with the detection of Brucella microti in farms raising marsh frogs (Pelophylax ridibundus), and the multiple investigations of anthrax clusters.
Expert appraisal activities
Several members of the unit are closely involved in expert appraisal structures within the Agency (working groups on tuberculosis in badgers or foxes, emergency collective expert appraisal group on highly pathogenic avian influenza [HPAI]) and outside (Epidemiological surveillance platform for animal health [ESA]), with participation in monitoring groups for bovine tuberculosis, bluetongue, West Nile fever and brucellosis.
The research carried out by the unit provides a better understanding of the functioning of epidemiological systems. It also documents the risks of emergence, and assesses surveillance and control schemes for regulated animal diseases in order to suggest improvements. The diseases studied are mainly those caused by the pathogens on which the microbiologists of the laboratory’s other units work.
The unit's research themes focus on complex epidemiological systems, due to the multiplicity and complexity of the contact networks that enable pathogen transmission, the existence of multi-host systems within which a pathogen is transmitted, and/or the intervention of vectors (such as mosquitoes or ticks) in pathogen transmission. Its methods involve the analysis of high-quality and often large datasets, which may be backed up by mathematical models of transmission. In 2017, the unit received funding for a computing server from the Île-de-France Region (DIM1Health).
Lastly, there are often long-term collaborations with the epidemiology units of other ANSES laboratories, as well as with external epidemiology units, in particular the French Agricultural Research Centre for International Development (CIRAD), the National Research Institute for Agriculture, Food and the Environment (INRAE) and the Institut Pasteur (within the framework of the IBEID Laboratory of Excellence).
The themes studied by the EPI Unit include:
- application of modelling, decision support tools and biostatistics to different animal pathogen models (tuberculosis in deer, bluetongue, trichinellosis, etc.);
- health monitoring, risk assessment and analysis, as well as emergency intervention systems applied specifically to monitoring vesicular-aphthous diseases, especially foot-and-mouth disease.
The unit's main research projects
Partners: Institut Pasteur, Virology UMR (ANSES Laboratory for Animal Health)
Funding: Ministry of Agriculture (thesis by an engineer from the Corps of Bridges, Waters and Forests, in continuing education through research), IBEID (Integrative Biology of Emerging Infectious Diseases) Laboratory of Excellence
The emergence of bluetongue virus serotype 8 (BTV-8) led to trade restrictions in France throughout 2007. Vaccination became available from 2008: a limited number of doses were first administered as part of an emergency vaccination campaign, followed by two national mandatory vaccination campaigns in 2009 and 2010. France regained its disease-free status in December 2012. The research group developed a model of BTV-8 transmission in cattle and sheep to analyse the relative importance of two methods of disease spread: active vector flight and movements of the infected ruminant. A second objective was to assess the effectiveness of control measures. The model was able to reproduce the BTV-8 epizootic wave. Host movements between distant pastures on the same farm were found to make a major contribution, as they caused more than 50% of the spread of BTV-8 to disease-free areas. This new finding raises practical questions about herd management during epidemics. The simulations also indicated a high level of compliance with the restrictions on animal trade. Without them, the whole of France would have been infected by the winter of 2007. The 2008 emergency vaccination campaign had little impact on the spread of the disease, as almost half of the vaccine doses were probably administered to cattle that were already immune. Moreover, the establishment of a vaccination buffer zone would have improved control of BTV-8 in 2008, limiting its spatial spread and reducing the number of infected cattle and sheep. The study also demonstrated the major role of mandatory vaccination in controlling the epidemic in 2009 and 2010.
Partners: French Agricultural Research Centre for International Development (CIRAD)
The structural risk of West Nile fever comes from the functioning of the socio-ecological system, which may favour the introduction and circulation of the pathogen, and the occurrence of human cases of the disease. Its geographical variations are due to local interactions between three components: reservoir hosts and vectors, which are both characterised by their diversity, abundance and competence, and the socio-economic context, which has an impact on human exposure to infectious bites. This project developed a structural risk model for West Nile virus (WNV) circulation in birds in Europe, and analysed the association between geographical variations in this risk and the occurrence of human cases of West Nile fever between 2002 and 2014. A meta-analysis of serological investigations of WNV in wild bird populations was conducted. This led to the development of a model of WNV seropositivity in European bird species, which is considered to be an indicator of the exposure of these birds to the virus. The study found that several eco-ethological characteristics of bird species were related to seropositivity. The fit of the statistical model was satisfactory (area under the ROC curve: 0.85). Combined with species distribution maps, this model yielded geographical variations in the structural risk of WNV circulation in birds. The association between this risk and the occurrence of human cases of West Nile fever in the EU was then assessed. Geographical variations in the structural risk of WNV circulation thus predicted the occurrence of West Nile fever in administrative districts of the EU with a sensitivity of 86% (95% CI: 0.79±0.92) and a specificity of 68% (95% CI: 0.66±0.71). The risk maps resulting from this study have been used to target surveillance and awareness-raising measures to stakeholders in the field in France.