Asymptomatic carrier animals are a serious food safety and human and animal health issue resulting in a significant loss to agri-food industry as well as a substantial burden on the healthcare system. On the human side, asymptomatic carriers may spread bacteria due to poor hygiene. This is especially problematic in the food industry, but is also an issue in hospitals and kindergartens. Many early studies assumed that susceptible hosts within a population had equal chances of becoming infected. Consequently, the majority of control measures and intervention strategies are based on the homogeneity of infection paradigm and the mathematical models of pathogen transmission. However, recent studies have uncovered the importance of host heterogeneity in infection, where a minority of the infected individuals are responsible for the majority of the infections.
The main novel aspect of this project is to take into account these recent studies on host heterogeneity in infection. In particular, it has been shown that the so called “Super-shedders” are responsible for the majority of the infections caused by pathogens transmitted via the faecal-oral route. “Super-shedders” are individual animals excreting significantly higher numbers of infective agents than other infected animals. Three of the most important zoonoses, namely salmonellosis, colibacillosis (E. coli) and campylobacteriosis are no exception to this general rule. Similarly, heterogeneity of human infection has been described for several pathogens as well as for carriage. More recently, we, and others, have demonstrated that gut microbiota can influence this infection heterogeneity. However, little is known about what distinguishes Super-shedders from other infected hosts and why some hosts are super-shedders and other low-shedders.
In this project, we will develop new approaches to predict, identify and prevent the appearance of animal Super-shedders and human long-term carriers based on immune response, gut microbiota composition and pathogen-specific characteristics. Moreover, developing new mathematical models of pathogen transmission within a population taking into account the heterogeneity of infection and the role of gut microbiota will help to test several intervention strategies in order to optimize husbandry and feeding practices, but also to reduce the antimicrobial use and spread of antimicrobials resistance genes. Models will incorporate indirect transmission via the environment to help optimizing bio-security measures. Models for the economic efficiency of our approach will enable an evaluation of the cost effectiveness of interventions. Our primary research on super-shedding will use Salmonella as a model for the other zoonoses.
This project is expected to have a substantial positive impact on the EU poultry and pig industry. It aims to reduce the impact of zoonotic pathogens in humans and livestock, improving health thus lessening the use of antimicrobial compounds and the risk of antimicrobial resistance.This multi-disciplinary project involves 12 Institutes from 10 countries (INRA-Tours, INRA Jouy en Josas, ANSES-Ploufragan, VRI-Brno, Vet-DTU, VISAVET-UCM-Madrid, University of Surrey, ISS-Roma, IZLER- Brescia, Wageningen Research-Wageningen, FHI-Oslo, NCOH-Wageningen.