Worried your cat might be making you sick? When it comes to Giardia, probably not. A new study published in PLOS One analyzed fecal samples from 157,616 cats across the US and Canada and found that while about 6% tested positive for any form of Giardia duodenalis, only 1.2% carried the genetic assemblages (A or B) that can actually infect humans — reassuring news for the millions of Americans who share their homes with cats.

The study also found that male cats, older cats, and intact (non-spayed/neutered) cats were more likely to carry the parasite. Regional patterns emerged too — Midwest cats had the highest prevalence, while cats in the South were least likely to test positive. Cold, moist winter conditions also correlated with higher rates.

Key Takeaways:

• Giardia can cause diarrhea, nausea, dehydration, hives, and swollen joints in humans, but cat-to-human transmission is rare
• Experts caution against routine fecal screening for asymptomatic cats, citing concerns about antiparasitic resistance
• The CDC recommends regular litterbox cleaning, keeping cats' fur clean, and keeping cats indoors to minimize risk

Why it matters: With pet ownership at an all-time high, understanding zoonotic disease risks helps pet owners make informed decisions — and this study suggests the focus should be on basic hygiene, not anxiety over your cat's litter box.