Rats in New York City were found to carry a flea species capable of transmitting plague pathogens, according to a recent study, the first study of its kind since the 1920s.
The research was conducted by Cornell University aided by Columbia University, and the findings were published in the Journal of Medical Entemology. Matthew Frye, an urban entemologist with Cornell's New York State Integrated Pest Management Program and his team collected more than 6,500 different specimens of fleas, lice and mites from 133 Norway rats, a species that is ubiquitous in New York City.
The Norway rat (Rattus norvegicus) is a cosmopolitan pest; it tends to live in close proximity to humans in urban environments and is a reservoir of many zoonotic pathogens. Human infection with rodent-borne diseases usually occur either directly through contact with a rat or its excreta or indirectly via arthropod vectors such as fleas and ticks. Frequent exposure to rodent hair, droppings and urine in the home or workplace is associated with asthma and allergies, especially in children.
Here, the journal reports on the diversity and abundance of ectoparasitic arthropod species and associated pathogenic bacteria from 133 Norway rats trapped over a 10-month period in Manhattan. The study found that Norway rats were host to the tropical rat mite, the spiny rat mite, the spined rat louse and the Oriental rat flea, with an average of 1.7 species per rat.
The study also found that rat fleas have the greatest chance of passing along human diseases, noting they were "notorious for their role in transmitting the bubonic plague, also known as the Black Death," said Frye in a news release. Black Death swept through Europe in the 14th century and killed an estimated 25 million people, or 30—60% of the European population.
"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," said Frye.