Rat Sampling Reveals Elevated Risk Of Zoonotic Disease in Urban Environments

MALAYSIAN BORNEO – 20, SEPTEMBER, 2022 Published in PNAS today, Rats and the city: implications of urbanization on zoonotic disease risk in Southeast Asia finds increased zoonotic disease risk in urban areas. The team surveyed three key components of zoonotic disease risk: 1) animal reservoirs 2) ectoparasite vectors and 3) pathogens. Research was done in partnership with EcoHealth Alliance, Australia’s national science agency, CSIRO, and James Cook University.

“As common dwellers of the urban city landscape, understanding the interaction and risks of disease posed by rodents to the human population is an increasingly important concern that needs to be addressed in urban city planning and development. This study provides some insights on the urban environments that foster these risky interactions and by extension provide direction on improving the urban landscape to minimize these health risks.” says Dr. David Perera, Director of the Institute Of Health and Community Medicine Universiti Malaysia Sarawak.

Rodents are a common animal reservoir for disease and suitable host for ectoparasite vectors. After sampling over 800 rats across an urban-rural gradient, researchers found decreasing rodent diversity in regions with increased urban development and identified two species that appear to be well-suited to urban living – Rattus rattus (the black rat) and Sundamys muelleri (Müller’s rat).

Figure. Effects of urbanization on zoonotic risk pathways

Figure: Effects of urbanization on zoonotic risk pathways

R. rattus carried a high diversity of pathogens and was associated with and reliant on developed areas with infrastructure supporting high-pathogen prevalence (sewers, trash, buildings, and roads). It was found to carry several pathogens at high prevalence that thrive in city environments, such as leptospirosis, which causes more than 1 million infections annually.

While both species were found to be infested with ectoparasite vectors, S. muelleri was associated more with ticks and found in high density in the green spaces of urban and developing areas. Additionally, both species’ urban populations had higher BMIs than their rural counterparts, speaking to their success in exploitation and adaptation of urban environments. The high density of both species provides a concerning look into spillover and transmission risk in cities. 

“Some species of rodent do really well in urban areas, which means there’s plenty of opportunities for people to come into contact with them and the pathogens they carry. Collectively R. rattus and S. muelleri occupied most of the environments we surveyed, so we need to raise public awareness that rodents and their diseases can be encountered almost everywhere, including in city centers.” stated Dr. Kim Blasdell, co-author and research scientist at CSIRO.

“Commonalities in the way we build and use cities around the globe does suggest that the patterns identified here are likely to be observed in other cities and countries, even when the animal species change. This means that by building on this type of work, it’s possible that we can reduce the potential impact of urbanization on disease risk. We can do this by building smarter cities that encourage safe environments for both people and wildlife to coexist, while reducing the types of environments where potentially risky animal-human contact can occur.” emphasized Dr. Cadhla Firth, co-author and Senior Research Scientist and Program Coordinator for EcoHealth Alliance.



Institute Of Health and Community Medicine Universiti Malaysia Sarawak (UNIMAS) 



James Cook University, Australia – https://www.jcu.edu.au/

Dedicated to helping the world’s tropical regions prosper.


Commonwealth Scientific and Industrial Research Agency (CSIRO), Australia – https://www.csiro.au/

As Australia’s national science agency, CSIRO works to solve the greatest challenges through innovative science and technology. 

Press Contact: Sian Stringer, sian.stringer@csiro.au


About EcoHealth Alliance:

Working with governments, scientists, and policymakers around the world to make critical changes for pandemic prediction and prevention. Our dedicated scientists conduct field research and develop tools to safeguard the health of the planet, people, and wildlife. Visit us at www.ecohealthalliance.org

Press contact: Majelia Ampadu, ampadu@ecohealthalliance.org