June 22, 2022 — Scientists have long suspected that rats could be one of the reasons cities are petri dishes for disease in a way not seen in rural communities. But a new study published in Nature ecology and evolution suggests that rats may not deserve this bad reputation.
To study the problem, scientists wanted to see if rats and other creatures living in cities carry different viruses or harbor more pathogens than animals in other settings.
When they looked at pathogens in nearly 3,000 species of mammals, they found that rats and other urban creatures could harbor up to about 10 times as many types of disease. But scientists have also discovered a potential blunder: Rats and city creatures are almost 100 times more likely to be studied as virus carriers.
That means scientists may have found more pathogens carried by rats and other urban creatures, because those are the mammals that researchers spend the most time studying.
“There are many reasons to expect urban animals to harbor more diseases, ranging from their food to their immune systems to their proximity to humans,” said the study’s lead author. , Gregory Albery, PhD, of Georgetown University in Washington, DC. statement.
“We found that urban species do indeed harbor more disease than non-urban species,” he said, “but the reasons for this seem to be largely associated with how we study disease ecology. We studied animals more in our cities, so we found more of their parasites.”
A bad rap
After taking into account that scientists much more often look for diseases transmitted by rats and other urban creatures, the researchers made a startling discovery, Albery said: city rats are no more fit than country rats. to harbor viruses that can infect people.
While the findings appear to absolve the city’s rats and other wildlife from being “hyper-reservoirs” of infectious disease, he cautioned that the city’s creatures are not disease-free.
“This probably means that urban animals aren’t hiding as many important new pathogens as we might think — those pathogens that could cause the next ‘disease X,'” Albery said. “But they’re still incredibly important carriers of many pathogens we know of. Rats, raccoons, and rabbits still coexist well alongside us, and they still spread many diseases to humans living in urban areas.”