Prevalence of Giardia in Cats Higher Than Expected

A recent study found that Giardia, a parasite that can cause diarrhea in cats, is more common than previously believed. Researchers analyzed over 157,000 fecal samples from cats in the United States and Canada and found Giardia in 6.3% of the samples.

Study Details and Researchers

The study, published in PLOS One on October 7, 2026, was led by Margaret Wingerd and conducted by Mars Veterinary Health and Antech laboratories. This rate of infection, nearly one in fifteen cats, is much higher than earlier estimates.

Understanding Giardia and Its Effects

Giardia duodenalis is a microscopic parasite that lives in the small intestine and causes diarrhea and stomach cramps. In cats, it often results in soft, recurring stools, but many infected cats show no symptoms, making it hard to detect without testing.

Scope and Timeframe of the Study

The research spanned from March 2022 to August 2023 and involved 157,616 fecal samples collected in the U.S. and Canada. This is the most comprehensive look at Giardia in cats in North America to date.

Risk Factors for Infection

Cats under one year old, male cats, and unneutered cats are at higher risk for Giardia. However, no cat is completely safe. Infections are less common in summer and more frequent in the American Midwest.

Lifestyle and Spread of Giardia

Outdoor cats that explore and sniff around are more likely to ingest Giardia cysts from other cats' feces. The parasite spreads easily in places like shelters and breeding facilities, where cats have frequent contact with each other.

Human Risk and Zoonotic Potential

About one in five Giardia-positive cat samples contained strains that can infect humans, classifying the disease as a zoonosis. In kittens, this proportion increases to nearly one in five. In humans, Giardia causes digestive issues that can last weeks or longer.

Prevention and Recommendations

While cats are one source of Giardia, water and food contamination remain the main causes in humans. Veterinarians advise annual fecal tests, especially for kittens and outdoor cats, and recommend good hygiene around food and litter areas to detect and prevent spread.