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NYC rats harboring fleas that can carry plague, other diseases, study says

A rat in New York City.

A rat in New York City. Photo Credit: Flickr/ Kai Schreiber

Fleas infamous for being able to carry the bubonic plague are living off the backs of the city's rats.

In a new study published this week, researchers say they literally went over 133 dead rats with combs and found that they harbor their own menagerie of vermin: fleas, mice and mites.

But it was the presence of more than 500 Oriental rat fleas that was the most unsettling discovery for the Cornell and Columbia university researchers. Oriental rat fleas have been known to play a role in bubonic plague transmission.

“If these rats carry fleas that could transmit the plague to people, then the pathogen itself is the only piece missing from the transmission cycle,” the study’s lead author, Matthew Frye, an urban entomologist at Cornell University, told the Cornell Chronicle.

The city’s Department of Health said the plague “requires extreme circumstances beside fleas to pose a threat to human health, and those circumstances do not exist here.”

“There has never been a case of locally-acquired plague in NYC — or anywhere east of the Mississippi — in over 50 years,” the DOH said.

The study by the Cornell and Columbia researchers was published March 2 in the Journal of Medical Entomology.

The researchers went to great length to try to identify “ectoparasites” and pathogens. Focusing their study on Norway rat, they live-trapped them at five places in Manhattan using Tomahawk Pro-Series Traps, luring them in with bits of chicken, cucumber or apple.

They were then euthanized, their carcasses fumigated and combed using a “fine-toothed flea comb over dry ice.” Forceps were used to “lift fur and abrade skin.” The parasites were “sorted visually and maintained on dry ice.” Molecular analyses was also performed.

According to the authors, it’s the first study of its kind to focus on rodent species from Manhattan since the 1920s.

Besides the notorious Oriental fleas, the study also found pathogenic bacteria that could “cause a wide range of clinical syndromes in mammalian hosts.”


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