One in 15 Cats Carries Human-Transmissible Giardia
A large-scale study finds 6.7% of North American house cats carry Giardia, with kittens and male cats at higher risk, and one in five infected cats carries strains transmissible to people.
One in fifteen house cats in North America tested positive for Giardia duodenalis, a gastrointestinal parasite. This finding comes from a study of over 150,000 domestic cat stool samples collected across 49 U.S. states and five Canadian provinces between March 2022 and August 2023.
The research highlights a significant zoonotic risk for cat owners. Giardia lives in the intestines of infected animals and people, spreading through stool. Only a few parasites are needed to cause illness.
Kittens and male cats show higher infection rates
Younger cats had the highest detection rates. Kittens were more likely to test positive than older cats. Neutered kittens, a group more commonly found in shelters where early-age neutering is standard, showed a markedly higher likelihood of infection.
Male cats were also more likely to be infected than females. Geographic trends emerged, with cats in the Midwest showing higher infection rates compared to other U.S. regions. Detection was less common during the summer months.
Parasite can spread to humans, posing risks to vulnerable households
One in five infected cats may carry strains of Giardia transmissible to humans. Some factors linked to higher infection rates in cats were also associated with carrying these zoonotic forms.
Individuals with vulnerable immune systems, such as young children, are at increased risk of complications. Humans are most often infected after drinking unclean water or through close contact with fecal material from infected individuals or pets.
Experts recommend routine testing and hygiene to prevent spread
Researchers and veterinarians stress the importance of routine fecal screening for domestic cats. Dr. Stevie Aitken, an emergency veterinarian, believes annual testing during wellness visits or when a cat shows symptoms is sufficient for most households.
She recommends more frequent screening if there are young children or immunocompromised individuals in the home. If a cat tests positive, thorough cleaning is imperative. Litter boxes, food and water bowls must be disinfected.
Areas where accidents occurred should be separated from at-risk individuals until treatment and re-testing are complete. General prevention includes hand washing and disinfecting areas soiled by diarrhea, as advised by the Centers for Disease Control.
Giardia causes gastrointestinal illness in both pets and people
Giardia duodenalis, commonly nicknamed 'beaver fever,' is found in every region of the United States and worldwide. It causes an intestinal illness called giardiasis. Symptoms generally begin one to two weeks after exposure.
Infections can result in diarrhea occurring between two and five times per day, leaving individuals feeling unusually tired. Other symptoms include upset stomach and bloating. While cases often resolve in under six weeks, severe infections can lead to long-term issues like chronic diarrhea, irritable bowel syndrome, joint inflammation, or nutritional deficiencies.
Infections can sometimes resolve without treatment, particularly in people with mild symptoms. Doctors may prescribe medication and supportive therapy for persistent cases, higher-risk individuals, or those likely to spread the infection. Veterinarians may also prescribe medicine for pets.
With cats living in nearly 80 million American households, understanding this widespread parasite is key. Experts recommend routine fecal screenings and thorough cleaning if a cat tests positive for Giardia.
