A new reasearch has found that millions of rats that thrive across New York City are susceptible to COVID-19. AP
New York City might need a Pied Piper soon. Its rats are getting more dangerous. The pandemic saw the population of rodents explode (they say there are as many rats in the city as people) and now a new study has found that they carry variants of the virus that causes COVID-19.
A study conducted by scientists from the United States Department of Agriculture, the Walter Reed Army Institute of Research and the University of Missouri and published in the American Academy of Microbiology’s journal mBio on Thursday said that rats can be infected.
The wild rats did not appear to get sick, lose weight or die when deliberately infected. But when the animals were exposed to the Alpha, Delta and Omicron variants of the coronavirus, researchers found evidence of robust viral replication in the animals’ noses, mouths, throats and lungs.
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How did the rats get infected?
Researchers captured 79 rats from three sites in Brooklyn in 2021 and tested them for exposure to the virus. They were trapped in city parks and some were caught near buildings from outside the park boundaries.
Evidence of robust viral replication was found in the noses, mouths, throats and lungs of the animals. Thirteen, or 16.5 per cent of the 79 rats were found to have IgG or IgM antibodies against the virus, suggesting a previous COVID infection. A PCR testing of their respiratory tissue suggested that four had active infections when they were euthanised.
A rat runs across a sidewalk in the snow in the Manhattan borough of New York City. The city has at least eight million rats. Reuters
“A number of studies have suggested that fragments of SARS-CoV-2 genomes were identified in sewage water systems and that the prevalence of SARS-CoV-2 in sewage water systems coincides with outbreaks in resident human populations,” according to the note by the researchers.
“However, no evidence has shown that SARS-CoV-2 viruses in sewage water are infectious, suggesting that sewage rats may have been exposed to the virus through airborne transmission, e.g. overlapping living spaces with humans or indirect transmission from unknown fomites, e.g. contaminated food waste,” it adds, according to a CNN report.
People aren’t known to pass the virus through food and W Ian Lipkin, a researcher at Columbia University’s Mailman School of Public Health, told USA Today that the precise route is unknowable.
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How dangerous is this?
The coronavirus has infected cats, dogs and hamsters. It has also affected deer, mink, otters, gorillas, lions and tigers. Millions of farm-raised mink were killed early in the pandemic to prevent them from infecting people.
While there is no evidence that these animals passed on the infection to humans, there is always a possibility for transmission, especially with animals that come in close contact with humans. Now there is every reason to be wary of rats.
Brown rats or Norway rats are found in abundance in New York. The city has close to eight million rats. They are known to transmit human diseases. Exposure to their faeces, urine or saliva can spread hantavirus, leptospirosis, lymphocytic choriomeningitis, tularemia and salmonella.
The population of rats exploded in New York City during the pandemic. AFP
As far as COVID goes, theoretically, if the rats can catch the virus from people, they can pass it back, according to researchers, the USA Today reports. This would be a particular concern if, say, they incubated a highly contagious vaccine-resistant variant.
The new study suggests a scenario where wild rats could become not only a vector for reinfection of humans but also a source of new variants that evade our protection from vaccines or past infections.
If the coronavirus recombines with another virus carried by rats, or if it simply evolves to spread more readily within that population, the result could be a novel pathogen capable of rebooting the pandemic, the study authors said, according to Los Angeles Times. The research emphasises “the need for further monitoring of SARS-CoV-2 in rat populations for potential … transmission to humans”.
The findings show the need for continued monitoring of rat populations to watch for the evolution of new strains of the virus, Dr Henry Wan, the study’s principal investigator and director of the Center for Influenza and Emerging Infectious Diseases at the University of Missouri said. He added that “it’s important that we continue to increase our understanding so we can protect both human and animal health”.
Lipkin said he’s more concerned about mice than rats because they come into closer contact with people, living in apartment building walls and often scurrying into inhabited spaces. “We have a more intimate relationship with mice,” he said.
The US team decided to study Norway rats after they found that rats in Hong Kong and Belgium were suspected of carrying the coronavirus. However, the latest research is reportedly the only one to show that the virus can infect urban rats.
Dr J Scott Weese, director of the Centre for Public Health and Zoonoses at the University of Guelph in Canada, told CNN, “There are lots of reasons to stay away from wild rats. The various things you can get from them, just add [Covid-19] to the list of reasons you probably shouldn’t be handling a rat.”
With inputs from agencies
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