Teeming With Trouble

Editor’s note: This article originally appeared in the April 17, 2018, edition of The New York Times with the headline “Urban Mice Are Teeming With Trouble, Study Shows.” It is reprinted here with permission.

Mice that live in the basements of New York City apartment buildings — even at the most exclusive addresses — carry disease-causing bacteria, antibiotic-resistant bugs and viruses that have never been seen before, a new study from Columbia University finds.

Researchers collected feces from more than 400 mice captured over a year in eight buildings in Manhattan, Brooklyn, Queens and the Bronx. The team then analyzed the droppings for bacteria and viruses.

The viruses included nine species that had never been seen before and others that have not been known to cause human disease, according to the study, published in April 2018 in the journal mBio.

But in a second study focused on bacteria, the researchers detected some of the most recognizable disease-causing pathogens, including Shigella, Salmonella, Clostridium difficile and E. coli. The scientists also found antibiotic-resistant bacteria like those that have become nearly untreatable at area hospitals.

It’s unclear whether the bacteria on the mice pose any health threat to people or have caused any human disease. But for centuries, rodents have been linked to illnesses like the Black Death.

“They are a potential source of human infection,” said Dr. W. Ian Lipkin, the epidemiologist at the Mailman School of Public Health at Columbia who was the senior author on the study. “The real message is that these things are everywhere.”

The mice appeared to be healthy, and Dr. Lipkin said he presumes that they are carriers of the bacteria but are not affected by them.

Dr. Lipkin said it was not clear whether the mice were getting the antibiotic-resistant bacteria from people — say, by eating food contaminated with the feces of someone taking antibiotics — or whether the bacteria developed resistance after mice ate discarded antibiotics.

It would be nearly impossible to conduct research directly linking a mouse pathogen with a human disease, said Charles Calisher, a professor emeritus at Colorado State University, who was not involved in the new studies.

The source of patients’ infections are rarely investigated, and they are not usually asked about their contact with mice, he said. “These are not simple things to investigate,” Dr. Calisher said.

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Peter Daszak, who heads the EcoHealth Alliance, a nonprofit that researches emerging diseases around the world, also described the research as difficult.

It’s crucial to identify and trace these microbes, he said, to help understand how they are transmitted and how, if necessary, to protect ourselves from the diseases they may carry.

“If we don’t know where they originate, we can’t identify what’s driving them and then we can’t control it,” said Dr. Daszak, who was not involved in the research.

No one knows, for example, whether antibiotic resistance genes emerged in hospitals, in cities or in rural areas.

This research is particularly important to do in New York, Dr. Daszak said, because the city is a destination for people from all corners of the world.

“New York is a major at-risk place for pathogens,” he said. “We’re certainly on the front line for emerging diseases.”

He said that the new research should not make New Yorkers more fearful of mice. “I’m not worried personally,” said Dr. Daszak, who lives in suburban Rockland County but works in the city. “Luckily, this is a species we’re already trying to control.”

Dr. Lipkin began researching New York City’s natural pathogens after the terrorist attacks of 9/11, when scientists realized they did not have a baseline to compare any changes. His lab has also studied rats on the New York City subway system and found many of the same infectious bacteria.

Although it is impossible to completely get rid of urban mice, Dr. Lipkin said his study suggests that more should be done to control mouse populations and their interactions with people.

Large apartment buildings should fill any gaps in their foundations, and trap and control any rodents found indoors, Dr. Calisher said.

Should everybody get a cat? “Cats have their own viruses,” Dr. Calisher noted.

(c) (2018), The New York Times.