Nearly one out of fifteen domestic cats in the United States and Canada carries Giardia duodenalis, a common gastrointestinal parasite that can transmit to humans, according to a study published in PLOS One. Researchers tested more than 150,000 fecal samples and found that roughly 6.6 percent of cats tested positive for the parasite, with one out of five infected felines harboring strains capable of infecting people.
Nationwide Testing Reveals 150,000 Samples Tested Across North America
The study, titled “Giardia duodenalis in domestic cats from the US and Canada: Prevalence and zoonotic potential,” analyzed clinical diagnostic samples collected between March 2022 and August 2023. Eleven researchers from Mars Veterinary Health and Antech Diagnostics examined submissions from 49 U.S. states and five Canadian provinces, according to ABC News. Dr. Anne Kimmerlein, co-author of the study and a global veterinary epidemiologist at Mars Veterinary Health, stated via ABC News that understanding how commonly the parasite occurs helps support earlier detection and appropriate treatment.
Kittens and Male Cats Face Higher Infection Rates
Certain cats face a higher risk of contracting the parasite due to age, sex, and environment. The study found that kittens under one year old tested positive more frequently than older cats, and male cats showed higher infection rates than females. Neutered kittens—frequently observed in shelter environments where sterilization occurs early—displayed a markedly higher likelihood of infection, which researchers attribute to exposure among rescued animals. Geographic and seasonal factors also influenced results, as Giardia appeared less frequently during summer months when warmer weather limits the parasite’s survival in the environment.
Beaver Fever Symptoms and Zoonotic Transmission Risks
Giardia duodenalis, commonly known as beaver fever since outbreaks linked to contaminated water near beaver habitats in the 1970s, infects the small intestine of humans and animals. Symptoms include diarrhea up to five times daily, stomach cramps, bloating, and upset stomach, which typically begin one to two weeks after exposure and resolve within six weeks. While many infected individuals and cats show no symptoms, severe cases can cause long-term complications such as chronic diarrhea, irritable bowel syndrome, joint inflammation, and nutritional deficiencies, with children and immunocompromised individuals facing the highest risks.
Veterinarians Recommend Annual Parasite Screenings and Strict Sanitation
Giardia infections often resolve without treatment in mild cases, but doctors and veterinarians can prescribe medications and supportive therapy for persistent infections. Dr. Stevie Aitken, an emergency veterinarian interviewed by ABC News, recommends routine annual fecal parasite screenings during pet wellness visits, with more frequent testing for households with young children or immunocompromised individuals. If a cat receives a diagnosis, owners must thoroughly sanitize litter boxes, food bowls, water bowls, and household accident areas while keeping pets separated from vulnerable family members until treatment and re-testing conclude. Kimmerlein told Gizmodo that pet owners should maintain preventive veterinary care and practice good hygiene around food, water, and pet waste.
Common Questions About Cat Parasites
Can indoor-only cats contract Giardia?
Yes. Dr. Anne Kimmerlein noted that Giardia was detected across a broad population of cats, meaning owners should not assume pets are safe simply because they stay indoors or live in a specific region.
How do humans typically catch Giardia from pets?
Humans are most often infected after drinking unclean water or coming into direct contact with the fecal material of infected animals or people.
What specific hygiene steps do veterinarians recommend?
Veterinarians advise washing hands thoroughly, preventing animals from licking human faces or mouths, and keeping children away from litter boxes.
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