In light of the recent COVID-19 pandemic, researchers have realized how important it is to learn more about the pathways through which illnesses are passed from animals to humans. Natural and anthropogenic factors interact to increase the risk of disease transfer from rodents to people, as shown in a study published in Nature Communications.
Reasons for rodents’ importance as reservoirs of infections include their “fast life,” or the fact that they reach sexual maturity at a young age, have several litters per year, and produce large numbers of offspring per litter. Yet the question remains as to why it is that rodent-borne diseases are so successful in infecting people.
Most rodents that are a potential source of zoonotic infections, which may be transmitted from animals to people, either experience dramatic population shifts, venture indoors at least periodically, or are actively pursued by humans for their flesh or fur. Research findings held true across different types of pathogens (i.e., virus, bacteria, fungi, and parasites). And moreover with modes of transmission, i.e., intermediate, involvement of vectors or non-close and close contact, with direct contact including breathing of contaminated aerosols, according to Frauke Ecke, project leader and Professor at University of Helsinki, Finland and senior lecturer at Swedish University of Agricultural Sciences (SLU) (SLU).
Researchers from Stockholm University, the University of Helsinki, and the Cary Institute of Ecosystem Studies in the United States used data from scholarly publications and databases to conduct a worldwide quantitative analysis that was published in Nature Communications.
The researchers looked at 436 species of rodents and found that 282 of them are reservoirs for zoonotic diseases. The researchers looked into how the reservoir status of rodents is related to their preferred habitat, population changes, and human hunting practices.
The study’s co-leader, Rick Ostfeld, comments on the surprising consistency of the findings across geographic locations, disease systems, and rodent species.
More importantly, the researchers have pinpointed hotspots where the possibility of human-to-mouse transmission is greatest. Dangerous areas include much of Europe, notably the continent’s center and northern portions, as well as a large portion of land stretching from Eastern Europe to Eastern Asia and China, as well as parts of South and Central America, the southern tip of Australia, and the eastern United States.
Ecke warns that there is a significant risk that if people encounter a rodent in these places, this rodent can transmit zoonotic infections.
Good examples of such pathogen-carrying rodents include the bank vole in Europe, the North American deer mouse, and Azara’s Grass Mouse in South America. Massive population shifts are seen among these creatures, and they are also able to adapt to interior environments.
Large population shifts, in addition to the disruption of rodents’ native habitat, may help explain why they start to inhabit areas near and even within human settlements. Generalists, or animals that can thrive in a variety of habitats, often exhibit this type of movement pattern. The vast majority of infections are carried by these generalists according to the researchers.
Sources:
Frauke Ecke et al. (2022). Population fluctuations and synanthropy explain transmission risk in rodent-borne zoonoses, Nature Communications. DOI: 10.1038/s41467-022-35273-7
https://phys.org/news/2022-12-humans-infected-rodent-borne-diseases.html
