The Cat Parasite That May Already Be Living Inside You — And Why You Should Care

Happy Caturday one and all. Before we get started, I want to emphasize that while the information below is important, it is in no way meant to imply or indicate cats are a danger to you or anyone. If you currently share your life with a furry feline — or are thinking about it — carry on. Consider this an important PSA on what you can do to protect yourself.  We are blessed to share our home and hearts with our kitten Cleo and 18 year old Dylan. These gorgeous, regal and yes, sometimes snooty creatures bring so much joy to millions of us. But it turns out joy may not be the only thing they bring. 

A new paper published this week in the journal PLOS Neglected Tropical Diseases is calling on the World Health Organization to formally designate Toxoplasma gondii a neglected tropical disease. What is Toxoplasma gondii (toxo) you ask? Toxo is a parasite that spreads through cat poop, contaminated food and water, and undercooked meat. Apparently, the infection known as toxoplasmosis has been “dangerously underestimated” for decades.

Forty-nine million U.S. households own a cat. If you live in West Hollywood odds are you are one of them. T. gondii is a single-celled parasite whose primary host is the cat. Cats catch it through intermediate hosts, usually rodents, which cats get by catching and eating. Talk about a catch 22.

For the sake of this story, we’re focusing on how humans can pick it up from infected litter. Again, the purpose of this is to educate you on how not to catch it, or if you have it how not to reactivate it.

Once you have toxo you have it for life. The good news: most of the time you’d never know it. The infection is often mild or goes completely unnoticed. Turns out about 1 in every 10 Americans is estimated to be living with it right now. Yeah, I did a double-take on that number too. Hence the headline.

The cases where toxo does cause harm can be serious, and in rare cases, fatal. 

West Hollywood has one of the largest HIV-positive populations per capita in the country. In people living with HIV whose immune systems are compromised, a dormant toxo infection can reactivate. The chances of reactivation reaches as high as 30 percent among patients with a CD4 count below 100 cells who are toxoplasma positive and not on effective prophylaxis or antiretroviral therapy. When that happens it most commonly attacks the brain. In the most severe cases, reactivation can be rapidly fatal. A study tracking U.S. death records over 11 years found 789 toxoplasmosis deaths — more than half of them in people also diagnosed with HIV.

A more common problem has toxo migrating to the back of the eye and inflaming the retina. Catch it late and you’re facing permanent scarring and vision loss. If you’re pregnant you especially need to be careful. Congenital toxoplasmosis can lead to miscarriage, neurological damage, and lifelong visual impairment.

Some of the research says toxo may also affect behavior and personality in humans, and may be linked to increased risk of schizophrenia or even brain cancer. In case you’re wondering, there is no vaccine. The drugs on hand today can manage flare-ups but cannot cure the infection.

The question most cat owners are asking? Can you catch it from loving your cat?

No.

Petting, cuddling, even sleeping next to your cat — none of that is harmful or a transmission route. The parasite lives in cat poop, not on the animal itself. The risk is in the litter box — and it is manageable once you understand exactly how it spreads.

Toxo gets into your body through your mouth, not your lungs. The most common way to get it from the litter box is hand-to-mouth. You clean the box, touch your face before washing up, and swallow oocysts you never saw. Catching it from breathing in litter dust is technically possible if dried litter becomes dusty and airborne, but it’s a rare route.

The CDC says ingestion is the primary risk. The parasite takes one to five days after being shed in feces to become infectious. If you scoop daily it breaks that cycle before it starts. Wear gloves and regardless, wash your hands with soap and warm water every time. If you are pregnant or immunocompromised, hand off litter duty to someone else entirely — if you can. If that’s not possible then you should definitely wear a mask for dusty litter.

Keep your cat indoors and on commercial food. Cats that don’t hunt carry very low risk of active infection.

Can you get tested?

Yes — both you and your cat. For humans, toxoplasmosis is diagnosed with a standard blood test. A doctor draws blood and checks for IgG and IgM antibodies. Results come back in one to three days. General screening is not currently recommended for healthy adults in the U.S., but if you are pregnant or living with HIV, ask your doctor about testing. For cats, your vet runs the same type of antibody blood test. A cat that tests positive for IgG antibodies has likely already fought off the infection and is probably immune — meaning it is not actively shedding the parasite. According to Cornell University’s College of Veterinary Medicine, those cats are no longer a source of infection for other hosts. High IgM levels suggest an active infection. Indoor cats that eat commercial food and don’t hunt are at low risk to begin with. Furtado’s message for cat owners is direct. “The key message is that toxoplasmosis is common, yet much of its burden is preventable. People should not panic, and cat owners should not blame or abandon their cats. The problem extends beyond cats alone,” he said.

The science here is not a reason to love your cats any less. It is a reason to wash your hands after the litter box and talk to your doctor if you are pregnant or HIV-positive.

Happy Caturday! Now go wash those hands.