The health of these cats is a bit less of a mystery thanks to a recent study<\/a> from researchers at Rowan and Long Island Universities. It\u2019s well-known that free-roaming cats can carry parasites and \u201cshed\u201d the eggs in their feces, which can then infect humans, pets and wildlife via contact with animal waste or soil in public places.<\/p>\n Unmanaged free-roaming cat populations, the authors write, \u201coccupy a critical interface between animal health, human health, and environmental hygiene.\u201d<\/p>\n But studies on this problem in New York City are rare, according to the researchers. The team tested nearly 90 cats across every borough except Manhattan in the late spring and summer of 2023. They found that more than half were infected with at least one parasite; 22% harbored two or more.<\/p>\n These results aren\u2019t surprising, said Felicia Nutter, a wildlife veterinarian at Tufts University, in an email to Mongabay.<\/p>\n The study establishes a baseline for cats in this area. Continuing to study this same population could help identify hotspots, track emerging parasite species and evaluate different management practices, she said.<\/p>\n The public health risk to humans is real, but \u201cunevenly distributed and mostly environmental,\u201d Nutter added.<\/p>\n \u201cThe results should be interpreted as evidence of preventable or manageable environmental health problems, not as immediate threat from casual contact with cats,\u201d she said.<\/p>\n The findings also highlight the vulnerability of pets and urban wildlife to parasites that can live long and range far through the environment.<\/p>\n Many cities, including New York, employ trap-neuter-return (TNR) programs to humanely manage stray and feral cat populations. This process of catching, spaying or neutering and releasing free-roaming felines gave the researchers a chance to test 87 cats for parasites between May and July 2023.<\/p>\n Common infections included the presence of Toxocara, a roundworm that may cause flu-like symptoms<\/a> in humans or in rare cases, may damage organs or vision. Both juvenile and male cats shed significantly more Toxocara eggs than adults and females, leading the researchers to dub young males \u201csuper-shedders.\u201d<\/p>\n About 14% of cats were infected with Ancylostoma, hookworms that can cause itching in humans as the parasites travel through the skin. A handful of cats also showed evidence of prior infection with Toxoplasma gondii, which can cause toxoplasmosis<\/a>, a potentially life-threatening condition for fetuses or immunocompromised individuals.<\/p>\n The New York City Health department told Newsweek<\/a> that the paper\u2019s findings don\u2019t change public health recommendations since \u201cthe risk to New Yorkers remains low.\u201d The department added that city residents \u201cshould wash their hands, avoid contact with animal waste and ensure pets receive routine veterinary care.\u201d<\/p>\n Toxocara and T. gondii can both infect and sicken pets and local wildlife. The risk varies considerably by parasite and wildlife species, Nutter said.<\/p>\n Toxocara can infect wild rodents, rabbits, shrews and birds, she said. The parasites\u2019 eggs are surprisingly hardy and aren\u2019t bothered by harsh winters in the northeastern U.S. They can still infect organisms after spending years in the ground.<\/p>\n Just about any warm-blooded vertebrate can be an intermediate host of T. gondii, including both terrestrial and aquatic birds and mammals, Nutter said, and the parasite can travel through both soil and waterways.<\/p>\n Most wildlife hosts are asymptomatic. But larvae migrating through animals\u2019 bodies can cause problems and parasites can prove deadly to some as they invade the brain or organs.<\/p>\n \u201cWhile only some of the parasites evaluated [in this paper] pose a risk to humans, they may pose a greater health threat to other cats, owned and unowned, dogs, and the many species of wildlife,\u201d the New York City health department told Newsweek<\/a>.<\/p>\n Existing trapping programs might offer a path forward.<\/p>\n The researchers suggest coupling these initiatives with parasite control strategies and targeting \u201csuper-shedders\u201d in particular. Administering antiparasitic drugs to young male cats during capture might be \u201cmore efficient, in terms of eggs removed from the environment per treatment, than uniformly treating all cats with low-intensity infections,\u201d they write.<\/p>\n Combining TNR programs with treatment and surveillance, along with other initiatives such as sanitation, adoption and abandonment prevention, would be \u201can excellent approach,\u201d Nutter said.<\/p>\n But there are logistical hurdles. Record-keeping, cat testing and environmental monitoring will need sustained resources and partnerships between TNR groups, veterinarians, public health departments and others, Nutter said.<\/p>\n \u201cIf a public health agency wanted the TNR community to help it monitor for parasitic diseases, it would have to provide a testing protocol for participating veterinarians as well as funding for the veterinarians\u2019 services in this regard,\u201d said Bryan Kortis, national programs director for the nonprofit Neighborhood Cats<\/a>, in an email to Mongabay.<\/p>\n The organization coordinates and supports TNR initiatives in New York City. It would rather see funding go to spaying and neutering, Kortis said.<\/p>\n \u201cIn the end, reducing the outdoor cat population in a manner that is humane and effective, and attracts grassroots participation, is the best way to reduce public health risks from outdoor cats,\u201d he wrote.<\/p>\n Nutter said that ultimately, \u201cabsolute reduction in the numbers of free-roaming and feral cats should be the goal.\u201d But broadly, the hope for TNR programs is more than that, she added.<\/p>\n \u201cThe overall goal of such TNR work, in my opinion, is not simply to reduce cat numbers or improve cat welfare,\u201d she said. \u201cRather, it is to manage the interface among humans, domestic animals, wildlife, and the ecosystem \u2026 to improve health and welfare across all domains while minimizing unintended consequences.\u201d<\/p>\n Banner image: Unowned, free-roaming cats in New York City. Trap-neuter-return programs can help sterilize and manage feral and stray populations in the city. Image courtesy of Neighborhood Cats.<\/p>\n Alex Megerle is an intern writer at Mongabay, where he covers wildlife and conservation and is a student in the Massachusetts Institute of Technology Graduate Program in Science Writing.<\/p>\n Citation:<\/p>\n Nguyen, V., Gurtowski, E., Chen, J., Rosen, M., & Kafle, P. (2026). Zoonotic endoparasites and Toxoplasma gondii seropositivity in free-roaming cats (Felis catus) from New York City boroughs. PLOS One, 21(7), e0351437. doi:10.1371\/journal.pone.0351437<\/a><\/p>\n FEEDBACK: Use this form<\/a> to send a message to the author or editor of this post. If you\u2019d like to post a public comment, you can do so at the bottom of the page.<\/p>\n More to explore:<\/p>\n Madagascar group aims to protect wildlife from stray cats & dogs<\/a><\/p>\n Cite this articleAlex Megerle (2026). Some free-roaming cats in New York City are parasite \u201csuper-shedders,\u201d study shows. Mongabay Conservation news. DOI: https:\/\/doi.org\/10.66709\/news-325347<\/a> <\/p>\n ![\"An](\"https:\/\/www.newsbeep.com\/us-ny\/wp-content\/uploads\/2026\/08\/2.-Neighborhood-Cats.png\")
An unowned cat in New York City. Researchers found that over half of the free-roaming cats they captured to spay or neuter in 2023 were infected with at least one parasite. Image courtesy of Neighborhood Cats.
\nThe parasite problem<\/p>\n![\"This](\"https:\/\/www.newsbeep.com\/us-ny\/wp-content\/uploads\/2026\/08\/6.-.png\")
This image shows the lifecycle of the Toxocara parasite, which can infect pets, humans and wildlife. Image courtesy of the U.S. Centers for Disease Control and Prevention.<\/p>\n![\"A](\"https:\/\/www.newsbeep.com\/us-ny\/wp-content\/uploads\/2026\/08\/3.-neighborhood-cats-3.jpeg\")
A cat trapped in New York City. Image courtesy of Neighborhood Cats.
\nManaging a free-roaming population<\/p>\n![\"Traps](\"https:\/\/www.newsbeep.com\/us-ny\/wp-content\/uploads\/2026\/08\/4.-Neighborhood-Cats-.jpg\")
Traps set for unowned cats in New York City. Researchers think combining cat management with disease surveillance could lessen zoonotic health risks. Image courtesy of Neighborhood Cats.<\/p>\n![\"A](\"https:\/\/www.newsbeep.com\/us-ny\/wp-content\/uploads\/2026\/08\/5.-TNR-release_Brooklyn.jpeg\")
A cat is released after being captured as part of a trap-neuter-return program in New York City. Image courtesy of Neighborhood Cats.<\/p>\n![\"\"](\"https:\/\/www.newsbeep.com\/us-ny\/wp-content\/uploads\/2026\/08\/92a8467a68ba6484f5372dc6c0c8580efd7d81cc823c1a1f46c9977026eb411e.png\")
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