More than half of New York City’s free-roaming cats carry intestinal parasites?

A study of free-roaming cats in New York City found that 57.5% were infected with at least one endoparasite, with Toxocara by far the most common. The findings highlight the role of urban cats in environmental contamination and suggest that Trap-Neuter-Return programmes could also become useful platforms for parasite surveillance and targeted control.

The study examined 87 free-roaming cats captured through a Trap-Neuter-Return programme between May and July 2023. Faecal, blood and molecular tests were used to detect gastrointestinal and vector-borne parasites.

Toxocara dominated the parasite burden

Overall, 50 of 87 cats (57.5%) carried at least one parasite detected by faecal flotation. The most common was Toxocara spp., found in 54% of cats, followed by Ancylostoma hookworms in 13.8% and coccidia in 11.5%. Co-infections were common: 21.8% of cats harboured two or more parasite species.

Among a subset tested by coproantigen assays, Giardia was detected in 11.6% and Cryptosporidium in 2.3%. Antibodies against Toxoplasma gondii were found in 8.9% of tested cats, indicating previous exposure.

Young males were the major Toxocara shedders

The most important epidemiological finding concerned parasite shedding intensity. Male cats had 4.36 times higher odds of Toxocara infection than females. Young cats also shed far more eggs than adults: their egg output was 8.74 times higher, while males shed 3.67 times more eggs than females. This identifies young males as potential “super-shedders”, contributing disproportionately to contamination of soil and public spaces.

That matters because Toxocara eggs are extremely resistant and can remain infectious in soil for years. Earlier environmental surveillance in New York found Toxocara eggs in 38.5% of public playgrounds, reaching 66.7% in the Bronx, with T. cati predominating.

An urban One Health issue

People become infected accidentally by ingesting embryonated Toxocara eggs from contaminated soil or hands. Children are particularly exposed because of hand-to-mouth behaviour and contact with sandboxes, parks and playgrounds. The authors stress, however, that detecting parasites in cats does not demonstrate that these animals caused specific human infections. The study measured parasite prevalence and shedding, not transmission to people.

The findings instead support a preventive One Health approach: incorporating deworming, parasitological surveillance and possibly targeted treatment of high-shedding animals into TNR programmes, alongside environmental hygiene and public education.

For large cities, free-roaming cats may therefore be more than an animal-population management issue. They can also act as sentinels — and reservoirs — for parasites circulating at the animal–human–environment interface.