One in 20 pet cats in North America may carry Giardia, study finds

Around one in 20 pet cats in the US and Canada may be infected with the intestinal parasite Giardia duodenalis, according to a large new analysis published in PLOS One.

The study, by researchers based in the USA and Colombia, examined more than 150,000 feline stool samples to estimate how common the infection is in domestic cats and to assess its potential to spread to people.

The findings point to clear risk factors. Young cats were more likely to test positive, as were male cats and those that had not been neutered. The researchers suggest these groups may warrant particular attention when clinicians consider testing and treatment.

Giardia is a common cause of diarrhoea in companion animals, although many infected cats show no clinical signs. Because some genetic types of the parasite can infect humans as well as animals, the authors also examined the zoonotic potential of the infections identified, a question of interest to veterinarians advising owners in multi-pet or family households.

The scale of the dataset makes this one of the most comprehensive pictures to date of Giardia in North America’s pet cat population. The authors declared no competing interests, and the work received no specific funding.

Reference: Giardia duodenalis in domestic cats from the US and Canada: Prevalence and zoonotic potential. PLOS One, published 7 October 2026. DOI: 10.1371/journal.pone.0358546