Why Humans Get Rodent-Borne Diseases – ScienceDaily
In a global study, researchers have found that most reservoirs of rodent-borne diseases tend to live exclusively or sporadically in or near human habitations, vary greatly in numbers, and/or are hunted for meat or fur.
The COVID-19 pandemic has highlighted the need to better understand the transmission routes of animal-borne diseases. The study shows how the risk of pathogen transfer from animals to humans is driven by the interaction between natural and human-induced factors.
The “fast life” of rodents with early reproductive maturity, many litters per year, and numerous young per litter is an important explanation for why rodents are important reservoirs of pathogens. But why do humans become infected with rodent-borne pathogens?
“Most rodents that spread zoonotic pathogens, i.e. pathogens that spread between animals and humans, range in large populations, move at least occasionally indoors, or are hunted for meat or fur. Our results were consistent in the types of pathogens, i.e. viruses, bacteria, fungi, and modes of transmission, i.e. intermediate , the involvement of vectors or non-close and close contact, close contact, including inhalation of contaminated aerosols,” says Frauke Ecke, project manager and professor at the University of Helsinki and lecturer at the Swedish University of Agricultural Sciences (SLU).
A worldwide survey of 436 rodent species
In a study published in Nature communicationResearchers from the University of Helsinki’s SLU and the Cary Institute of Ecosystem Studies in the USA conducted a global quantitative study based on data collected from research papers and databases. The study includes 436 rodent species, of which 282 are all known reservoirs of zoonotic pathogens. The researchers found out the connection between the environmental choices of rodents, the variation in numbers, i.e. population variations, the hunting of rodents by humans and the status of rodents as reservoirs.
“It is remarkable how consistent the results are across continents, disease systems and rodent species,” says Rick Ostfeld, co-director of the study.
Some areas of the world are more at risk of getting zoonoses from rodents
In addition, researchers have identified areas where the risk of infection between rodents and humans is high. Much of Europe, especially central and northern Europe, a large area from eastern Europe to eastern Asia, eastern China, parts of South America, southeastern Australia, and eastern regions of North America are at high risk.
“If people encounter a rodent in these areas, there is a high risk that this rodent carries zoonotic pathogens,” says Ecke.
Examples of such pathogen-carrying rodents include the bank vole in Europe, the North American deer mouse, and the Azara’s Grass Mouse in South America. The population of these species varies greatly and they can also move indoors.
“Especially large population fluctuations together with the disturbance of the rodents’ natural habitat can explain why rodents move close to and into human dwellings. This movement behavior is typical of so-called generalists, which are species that survive on many different things. These generalists are the most important reservoirs of pathogens,” Ecke explain.