Mouse poop discovery may hold answers to asthma rates in NYC

Oh, hell gnaw!

As if you need another reason to avoid mice in NYC, researchers at Weill Cornell Medicine have identified a fungus in city mice that aggravates food allergies.

The study authors note that there’s a high prevalence of human asthma in NYC neighborhoods with an abundance of mouse sightings, suggesting that all that mouse poop could be to blame.

Researchers at Weill Cornell Medicine have identified a fungus in the stomach of NYC mice that exacerbates their food allergies. It’s unclear the effect it has on humans. Getty Images

The fungus, Kazachstania pintolopesii, is found in the stomaches of these mice and shed in their feces. While more research is needed to determine what happens when humans are exposed to it, the study draws a link between it and asthma in humans nearby.

“You can see that in the Bronx, you can see that in certain areas of Brooklyn,” senior study author Iliyan Iliev, an associate professor of immunology, told The Post.

It’s unclear if the fungus is present in the guts of humans, rats or other animals — and if it has the ability to “jump” hosts.

In mice, the fungus can spur a type 2 immune response, which protects the critters against worms and other parasites but also exacerbates food allergies.

“There is a lining of the gastrointestinal tract, which is a mucus layer, so it protects us against pathogens,” Iliev explained.

“If diet changes or if antibiotics are taken, the mucus layer is basically shrinking,” he continued. “That leads the fungus to get in very close contact with the epithelium underneath and with the immune cells, and that produces this type 2 immunity response.”

Iliev pointed out that this response is good for mice because they are often exposed to parasites, but this benefit may not help humans much.

The fungus Kazachstania pintolopesii (in red) is detected in the mucus (green) of the mouse stomach (blue). Dr. Yun Liao, The Iliev Laboratory at Weill Cornell Medicine

Iliev’s team identified the fungus in mice captured in NYC, Los Angeles and Maryland farms as well as in lab mice. They plan to widen their net to see if this fungus is present in mice elsewhere.

“The mice in the big cities, they are close to the human population,” Iliev said. “They are getting into their houses, into the gardens, into the parks and everywhere.”

NYC mice are prone to making their home inside buildings, while rats thrive on streets and in alleys here.

Mice can contaminate food with their droppings, and they can leave behind urine, saliva and hair that contain proteins that act as allergens, worsening asthma symptoms in humans.

Iliev said further research is needed to determine if increased incidence of asthma is related to mice urine or dander, the fungus shed in feces or other factors altogether.

The Weill Cornell Medicine findings were published Wednesday in the journal Nature.

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Allergies can trigger asthma symptoms. Mice have long been associated with allergens. Getty Images

Iliev hopes these preliminary results enlighten researchers about this fungus, especially if they are developing drugs that will be tested on mice or using mice to study allergies or parasite infections.

The team plans to learn more about how the fungus elicits the type 2 immune response and if it’s present in the gut microbiome of other animals, like rats.

“That’s what we are very interested to learn,” Iliev said about rats. “They share similar habitats. The internal temperature in the stomach and in the gastrointestinal tract are very similar, so I don’t see why [the fungus] would not survive also in other animals.”