TRANSVI: improving our understanding of the transmission of zoonoses

Objectives

The increasing prevalence of zoonotic viruses highlights the crucial importance of characterising the transmission chains of certain viruses of public health concern between wildlife populations and human populations. The TRANSVI project (standing for ‘Characterising the chains of transmission of zoonotic viruses between wildlife and humans: the case of coronaviruses and hantaviruses in the Yucatan Peninsula (Mexico)’) therefore aims to characterise each of these stages and to define how their interactions may impact the emergence of zoonoses.

This project, which forms part of Céline Arnathau’s PhD thesis, proposes a comprehensive and innovative approach to better understand, prevent and control future zoonoses by characterising each stage of the viral transmission chain in an environment conducive to the development of potential new pandemics. In the medium term, this project will identify the bat and rodent species to target in order to strengthen surveillance systems, as well as to improve the development of prevention strategies to limit transmission to human populations.

The project also aims to characterise the ecological interfaces between bats, rodents and humans, i.e. the contexts in which these species come into direct or indirect contact, which may facilitate interspecies transmission.

Better characterising the role of animal species

Bats are the natural reservoirs of many zoonotic viruses, but their role in environmental viral shedding remains poorly documented. However, the environmental shedding of zoonotic viruses by bats can lead to the infection of intermediate species, such as rodents, which share part of their environment with bats and humans, thereby facilitating viral transmission. This project therefore seeks to determine whether rodents act as a bridge between wildlife and human populations in viral transmission. More specifically, the TRANSVI project will focus on the potential emergence of two RNA viruses, coronaviruses and hantaviruses, known to cause haemorrhagic fevers or respiratory viral infections once adapted to humans.

Initial results from sampled animal species show the existence of a dilution effect in conserved habitats, where greater animal biodiversity is associated with reduced hantavirus circulation, whilst this effect tends to disappear in anthropised environments. These results thus suggest a protective effect of biodiversity against the risk of zoonotic transmission.

Identifying viral strains and assessing human exposure

By focusing on vulnerable human populations in the Yucatan Peninsula (Mexico), a region recognised as one of the potential hotspots for the emergence of zoonoses, the first part of the project aims to identify coronaviruses and hantaviruses circulating among bats and rodents by assessing the presence of similar viral strains in bat droppings (or guano), as well as in blood samples from bats and rodents. This work will enable the compilation of an inventory of the targeted viruses circulating in bat and rodent populations, as well as determining the impact of environmental viral shedding via faeces on rodent exposure.

The aim is also to better understand how changes in habitats and ecological interfaces influence the dynamics of viral circulation and the risks of ‘spillover’, i.e. the transmission of a pathogen from wildlife to human populations and vice versa.

The second work package will assess the role of bats and rodents in human exposure to the same viruses. This component will statistically analyse the link between human exposure—derived from an ongoing serological study conducted in villages near animal sampling sites—and the circulation of these viruses among bats and rodents. This analysis will also incorporate factors promoting contact between human populations and bat/rodent communities (outdoor activities, consumption of bat meat, etc.) identified during a socio-epidemiological study in order to identify transmission routes.

Collecting socio-epidemiological data

Over the past three years, intensive sampling of bat and rodent species has been carried out at three sites on the Yucatan Peninsula, all located near vulnerable human populations. Blood samples from bats and rodents at these sites are already available, and collection will continue from 2025 to 2027.

External projects are funding the collection of serum from three human populations near the bat/rodent sampling sites. TRANSVI is funding the collection and analysis of bat droppings collected in the field, as well as the analysis of blood samples already obtained (PCR and sequencing). The project also supports the serological analysis of human serum samples (Luminex), as well as the collection of socio-epidemiological data to identify exposure factors within human communities.

The role of ANRS MIE

The TRANSVI project received funding of approximately €200,000 over three years from ANRS MIE as part of its annual call for projects, “Émergences PRFI”, in 2024.

This scheme aims to support collaborative research projects between a French team and a team from a low- or middle-income country (LMIC), focusing on global issues related to MIE. It is fully in line with the ANRS MIE’s missions, supporting high-quality, partnership-based research with a significant impact on populations, using a comprehensive approach.

The research projects supported by this scheme are distinguished by their local roots, linked to healthcare or surveillance systems; their potential impact on public health in the countries concerned; and their ability to generate original data and foster sustainable scientific collaboration.