DESIRE: Developing evidence-based surveillance for emerging rat-borne zoonoses in changing environments
Brown (Rattus norvegicus) and black rats (R. rattus) can carry a multitude of pathogens with public and veterinary health importance. Their potential to rapidly reach high population numbers creates unpredictable situations of high pathogen transmission risks. Rat populations depend on anthropogenic factors, such as the use of rodenticides and on unintended food provisioning. They are also heavily affected by environmental changes, including urbanization and climate change. A new phenomenon with yet unknown consequences for rat-borne diseases is the “greening” and “blueing” of cities to improve living conditions and biodiversity and to combat heat. In addition to these risks in the urban environment, there are numerous examples of the (potential) role that rats have in food contamination and the transmission of pathogens of veterinary and human health importance (e.g. avian influenza or zoonotic hepatitis E virus in rats around pig farms and antimicrobial resistance. Therefore, the wicked problem of rat-borne diseases is an excellent example of a One Health topic that is highly relevant for (re-)emerging threats, and is linked to the topics of antimicrobial resistance and foodborne zoonoses.
Rats are synanthropic animals and with their incredible ability to adapt to new environments, they will always be part of the human living environment. Sustainable interventions will therefore need to be directed to situations where the risk of transmission of pathogens creates human or veterinary risks. In order to perform risk assessment and to mitigate the risks, a surveillance system is needed that has information about both pathogen distribution as well as rat population developments.
Yet, the knowledge of rat-borne pathogens in European cities is surprisingly scarce. Existing studies mainly focus on the emerging zoonotic pathogens Leptospira spp. and Seoul orthohantavirus, but the number of zoonotic pathogens carried by rats is much larger. Information about rat populations, a vital element in risk assessment, is fragmented at best. In addition to zoonotic pathogens, an increasing number of agents with unknown zoonotic potential has been described by next generation sequencing and broad spectrum PCR methods. The knowledge gaps in the current surveillance system hamper risk assessment, early detection of changing risks, and adequate responses. Interventions for rat-borne zoonoses need a One Health approach, taking into account the environment and social sciences. Targeting the carrying capacity of the environment as an intervention is of increasing importance now that traditional interventions based on rodenticides are not an effective long-term solution due to development of rodenticide resistance, and may even be increasing the prevalence of rat-borne diseases.
The overall aim of this project is to design and test an effective surveillance system for rat-borne diseases, using The Netherlands as a testcase. The PhD-student will contribute to the surveillance of rat-borne diseases by providing evidence-based insights in four key elements of this surveillance system: i.e. monitoring of populations, monitoring of pathogens, risk-assessment and intervention. The PhD candidate will build onto existing surveillance activities and extend these by collaboration with (inter)national institutes.