Millions of Cats Carry Parasite That Can Infect Humans

A significant study involving over 150,000 cat samples across the U.S. and Canada has found that approximately one in fifteen household cats carries the Giardia parasite. This common organism, also known as "beaver fever," can be transmitted to humans. Researchers identified that about 20% of infected cats harbored strains capable of infecting people, prompting a closer look at human-pet interactions.

The findings, published in PLoS One, indicate that younger cats and males were more frequently infected. Neutered kittens, particularly those from shelters, showed a higher risk, likely due to increased animal contact in rescue environments. Infection rates varied geographically, being higher in the Midwest, and were influenced by season, with cooler, moister conditions favoring the parasite's survival.

Giardia resides in the intestines and is shed in stool, making it easily transmissible. Humans typically contract it through contaminated water or close contact with feces. Symptoms, appearing one to two weeks post-exposure, can include severe diarrhea, stomach upset, and bloating. While most human cases resolve within six weeks, severe infections can lead to long-term health issues. Infected cats may exhibit symptoms or remain asymptomatic, underscoring the need for veterinary testing.

Veterinarians recommend thorough cleaning of litter boxes, food, and water bowls if a cat is diagnosed with Giardia. Pet owners are advised to practice good hygiene, such as regular handwashing, and to keep litter boxes away from young children and immunocompromised individuals. Annual veterinary check-ups are crucial for detection, with more frequent testing recommended for households with vulnerable individuals. Medications are available for treating infected cats and humans.