Cats may be cute and adorable, but stray and feral cats can sometimes pose a risk to human health. Veterinary researchers have discovered that more than 50% of free-roaming cats in New York City carry parasites that could potentially be transmitted to humans.
The Big Apple has a cat problem, with colonies scattered throughout the city. While all animals harbor potential disease-causing organisms like viruses and bacteria, little was known about the prevalence of zoonotic parasites (parasites that can jump from animals to humans) among New York's street-dwelling cat population.
Researchers from Rowan University and Long Island University in New York examined blood and fecal samples from 87 outdoor cats captured through the city's TNR (Trap Neuter Return) program.
To look for parasites, they mixed stool samples into a special liquid that makes eggs float to the surface, a technique called fecal flotation. This allowed the team to count the number of eggs under a microscope. They also used tests to screen the samples for specific parasite proteins, DNA and antibodies that might reveal past exposure to parasites.
Hidden hitchhikers
The findings, published in the journal PLOS One, showed that parasitic infections are incredibly common among the city's outdoor cats. "Overall, 57.5%... of cats were positive for at least one endoparasite species detected by fecal flotation," the team wrote in the paper.
The dominant parasite was Toxocara, a roundworm that can infect humans through contaminated soil containing microscopic eggs shed in cat feces, causing the disease toxocariasis.
"Male cats were significantly more likely to be infected with Toxocara spp. (OR = 4.36) and, along with juvenile cats (<1 year), shed significantly higher numbers of eggs ... identifying young males as high-intensity 'super-shedders' driving environmental contamination."
Ancylostoma species, a genus of hookworms, were also common, occurring in 13.8% of the animals. Some species of these parasitic worms can infect people, usually by penetrating the skin, although some can also infect the human intestine.
The third most prevalent type of parasite was coccidia, single-celled protozoa that infect the intestinal tract. In total, about one in five cats were infected with multiple parasites at the same time.
Analysis of the blood samples revealed past exposure to Toxoplasma gondii, meaning some cats had previously been infected but were not necessarily actively shedding the parasite.
Protecting public health
Because of the potential threat to public health, the study authors recommend combining disease tracking and parasite treatments, where possible, into TNR programs throughout New York City.
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Publication details
Viet-Linh Nguyen et al, Zoonotic endoparasites and Toxoplasma gondii seropositivity in free-roaming cats (Felis catus) from New York City boroughs, PLOS One (2026). DOI: 10.1371/journal.pone.0351437
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Citation: Hidden health risks found in New York City's free-roaming cats (2026, July 10) retrieved 11 July 2026 from https://phys.org/news/2026-07-hidden-health-york-city-free.html
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