One in 15 Cats Are Carrying a Diarrhea-Causing Parasite, Study Shows

Research out today offers a potential warning for cat owners everywhere: your precious feline might be harboring a parasite that can cause trouble for your toilet and their litter box at the same time. Veterinary scientists studied clinical lab samples sent in from across the U.S. and parts of Canada. Roughly one in every 15 cats seems to be carrying a diarrhea-causing parasite known as Giardia duodenalis, they found, some strains of which can also sicken humans. Though the infection is manageable, especially when caught early, the findings highlight the importance of keeping a close eye on your cat’s gastrointestinal health, the researchers say. “Giardia is a parasite veterinarians know how to diagnose, treat, and help prevent, but some infected cats may not appear sick,” study author Anne Kimmerlein told Gizmodo. “It’s important that pet owners keep up on recommended preventive veterinary care, including fecal parasite screening tests.” A common parasite Giardia is a parasitic protozoan. In its hosts, it infects the small intestine, causing diarrhea, stomach cramps, and other GI symptoms. Though the illness usually only lasts a few weeks in humans, some unlucky few can develop chronic gut issues. Eventually, new generations of the parasite are pooped out, allowing them to contaminate the environment as hardy cysts and start the cycle all over again. There are several major types of this particular species of Giardia, two of which can easily infect humans as well as other mammals like cats. Giardia is actually the most common parasitic disease in the U.S., with more than a million cases seen every year, according to the Centers for Disease Control and Prevention; it’s an even larger problem in developing countries that have inadequate sanitation. Though vets routinely encounter Giardia in cats, there’s surprisingly not much large-scale data we have on it, according to the authors. Kimmerlein is a global veterinary epidemiologist with Mars Veterinary Health, a division of Mars Petcare, which oversees several large networks of vet clinics in the U.S. and elsewhere. For this study, she and her colleagues teamed up with researchers from Antech Diagnostics, also a part of Mars Petcare, which operates clinical diagnostic labs around the globe. The team studied more than 150,000 domestic cat fecal samples submitted to labs across North America between March 2022 and August 2023. These samples came from cats in 49 states and Washington D.C., as well as five (out of 10) provinces in Canada. Ultimately, 6.3% of the samples tested positive for Giardia. Of these, around 18% were positive for the two types that can infect humans. The risk of infection was highest among young, male, and unneutered cats, though it can potentially infect any feline, the researchers point out. “While the study identified differences by age, sex, season, and geography, it’s important to note that Giardia was detected across a broad population of cats,” Kimmerlein said. “That means pet owners shouldn’t assume their cat is not at risk simply because they live in a particular region or spend most of their time indoors.” The team’s findings were published Wednesday in the journal PLOS One. Lessons to take away Many people and cats infected with Giardia will never become sick as a result. And cats are only one of the potential routes of Giardia transmission for people. We can also catch it from contaminated water and food or from close contact with other infected people and/or the poop-laden surfaces they touch. Still, this risk shouldn’t be ignored, the researchers say. When left untreated, Giardia can cause serious problems for both cats and humans alike. Veterinary organizations generally recommend that owners have their cat’s poop screened for Giardia and other germs at least once a year (more so if they’re younger or outdoor cats). And if you suspect that your cat might be sick with it, there are steps you can take to prevent any further transmission to yourself or any other pets you own, the researchers note. “Pet owners should be aware of the signs of gastrointestinal illness, practice good hygiene around food, water, litter boxes, and pet waste, and work closely with their veterinarian if concerns arise,” said Kimmerlein.