What Are the Real Effects of Toxoplasmosis?

If you’ve ever seen a mouse run up to say “hello” to a cat or stop to let himself be sniffed, you might have wondered how an archnemesis could turn into a fast friend. But there’s a very good reason why a rodent might suddenly lose their fear around a cat who may eat them. 

Toxoplasmosis is a zoonotic parasitic disease caused by Toxoplasma gondii—and not only does it affect animals, but it infects a significant percentage of humans, too, says Dr. Mani Lejeune, the director of clinical parasitology at the Cornell University College of Veterinary Medicine.   

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There are lots of questions and myths surrounding toxoplasmosis—like, can you get it from your pets? Do your cat and dog likely have it? Do you? And if you’re infected, does it make you fall in love with the smell of your cat? The internet is obsessed, so we asked some experts to help us differentiate between truth and rumor. 

Domestic cats can spread toxoplasmosis: True 

Toxoplasma gondii cannot maintain its lifecycle without felids—that’s any type of cat, from housecats to tigers. 

“It can infect almost any warm-blooded animal, including people, but cats are the main host, meaning the parasite completes its life cycle in cats,” says Dr. Alyssa Cornelius, the interim medical director at VCA New Hartford Animal Hospital in New York. 

The parasite cycles between felids and other hosts, like other mammals and birds. 

“A naive cat can contract the parasite by eating infected prey, such as rodents or birds, or by consuming the meat and offal of infected domestic or wild animals,” Dr. Lejeune says. In urban areas, this is likely to be domestic cats eating mice or birds, he says, while “in the wild, it occurs between any felids and their prey, such as bobcats and white-tailed deer.” 

Dogs can’t get toxoplasmosis: False  

Unfortunately, dogs are fair game, though the parasite is rarer in the canine species. 

“Toxoplasmosis is more common in cats than in dogs,” says Dr. Veronica Villanueva, the medical director at VEG Anaheim Hill in California. “Cats commonly get infected from ingesting contaminated meat from rodents or birds.”

There’s a 1 in 3 chance you have toxoplasmosis: True    

Many people have never heard of toxoplasmosis, but there’s a chance you could have it. How would you know? You probably wouldn’t, as most healthy people do not exhibit symptoms, according to the Centers for Disease Control and Prevention. 

And, to be fair, 1 in 3 is a global estimate. In the U.S. specifically, one study suggests that up to 22 percent of the population might be carriers—still a nearly 1 in 4 chance—while the CDC says at least 40 million Americans are carriers, which is, at minimum, 11 percent of the population. Some estimates even say as many as 60 million Americans are infected with Toxoplasma gondii.  

You’re most likely to get toxoplasmosis from your pet: False  

If you do have toxoplasmosis, it’s unlikely you contracted it from your pet. 

“Although cats play a role in the parasite’s life cycle, humans usually get toxoplasmosis from food, not from pets,” Dr. Cornelius says. 

Dr. Lejeune agrees that the biggest risk is “consuming raw or undercooked meat, such as pork or game…rather than exposure to cats.” 

If your pet is diagnosed with toxoplasmosis, don’t panic. The transmission from pets to humans is generally low if you practice good hygiene when cleaning up their poop, Dr. Villanueva says. 

“If your cat or dog is diagnosed, just practice normal hygiene—wash hands, clean litter boxes daily, keep raw meat away from pets—and seek veterinary care for appropriate treatment,” Dr. Cornelius says. 

If you’re pregnant, you shouldn’t scoop cat litter: True     

That said, you can get toxoplasmosis from a litterbox—specifically, your cat’s poop. But the risk is quite low when proper hygiene is practiced, Dr. Villanueva stresses. 

“For pregnant women, it is extremely unlikely to contract toxoplasma from cleaning a litter box, but there is still a slight risk,” she notes. “Since the parasite can be transmitted to the baby, it is best for pregnant women to avoid this task altogether, if possible.” 

Dr. Lejeune says that cleaning the litter box daily can significantly lower the risk of human transmission but agrees that it is safest for pregnant women to avoid scooping. 

If you are pregnant and the only one who can take care of your cat, be thorough in protecting yourself: “Taking precautions, like wearing gloves and washing hands thoroughly afterward, can also minimize the risk of infection,” Dr. Villanueva says. 

Adds Dr. Cornelius: “The eggs cats shed in their litter box take one to five days to become infectious, so if you scoop daily, the risk is almost zero.” 

Toxoplasmosis makes mice “friendly” around cats: True  

When a rodent like a mouse or rat loses their fear around a natural predator, they’re opening themselves up to be prey—and toxoplasmosis is often to blame if the parasite encysts in the part of the brain responsible for processing smell perception or emotions like fear, Dr. Lejeune says. 

“The mice may lose their aversion to cat urine and could even befriend the predator,” he explains. “Other rodents and wildlife may also exhibit these signs, which increase the risk of being preyed upon.” 

So, if you see a viral video of a cute mouse cozying up to a natural enemy, it’s not as adorable as it may look—it’s probably toxoplasmosis. 

If you’re infected, you’ll love your cat more: False 

The reason you love your cat so much is probably because they’re elegant yet goofy, aloof yet affectionate, and the best thing in your life aside from fresh air. But does a human infected with toxoplasmosis feel even more affection for their cat, as the internet seems to believe? 

“There is no evidence linking people’s obsession with cats to them being infected with toxoplasmosis,” Dr. Lejeune says. “For this to happen, the parasite must enter the brain and affect a specific area responsible for such behavior, but evidence shows that Toxoplasma gondii mostly affects the brains of people who are immunocompromised…. The clinical symptoms documented in such patients are vague but include headache, altered consciousness, dizziness, or seizures.” 

In people with a healthy immune system, he adds, the disease presents with mild flu-like symptoms. But there is no scientific evidence that shows an increased love for the feline species. (Sorry, TikTok.) 

Toxoplasmosis can change your personality: True 

It might not be the reason you’re obsessed with your cat, but there could be a link between toxoplasmosis and personality changes in humans. 

“While a few studies have tried documenting personality changes that are nonclinical, the majority have documented the parasite association with aberrant behavioral changes and psychiatric disorders,” such as depression and schizophrenia, Dr. Lejeune explains. Still, he notes that this is “a neglected disease with its public health impact not documented to the fullest.” 

If you’re infected, your cat will smell like fresh laundry: False 

It may sound ridiculous, but TikTok’s mind is made up: Many videos show pet parents smelling their cats and declaring the smell “like fresh laundry” or something else delightfully pleasant.   

The rationale is that their attraction to their cats’ scent is a result of their own toxoplasmosis infection changing the way they smell their cat. However, “there is no confirmatory scientific evidence,” Dr. Lejeune says.

Meat-based raw food diets may contain the parasite: True  

According to the Merck Manual, there are lots of reasons to be concerned about meat-based raw pet food, but you can add toxoplasmosis to the list.  

“Raw diets can contain Toxoplasma gondii cysts,” Dr. Cornelius says, noting that raw or undercooked meat can infect both pets and the people handling it. “Cooking meat thoroughly and washing hands and surfaces after handling are the best preventives.”

Toxoplasmosis doesn’t show any symptoms in pets: False 

You might not know if your pet has toxoplasmosis right away—or ever, Dr. Villanueva says. However, if your pet does experience symptoms, they might be:  

• Fatigue 

• Changes in activity level, such as being less playful

• Loss of appetite 

• Vomiting 

• Diarrhea 

• Fever

• Difficulty breathing 

• Neurological signs, such as seizures or being uncoordinated  

Keep in mind that these symptoms can describe many conditions, not just toxoplasmosis, and most pets with a healthy immune system won’t show symptoms at all. No matter the cause, a high fever, difficulty breathing, or sudden neurological issues are all reasons to see an emergency vet immediately. 

There’s no way to detect toxoplasmosis in your pets: False 

Dr. Villanueva says that pet parents can ask to have their pet’s poop checked for Toxoplasma gondii and other parasites every six to 12 months. If your pet tests positive, treatment may include an antibiotic. 

“In many cases, with prompt treatment, pets can recover well from the infection, but outcomes can vary depending on the severity and the general health of the pet,” Dr. Villanueva says. 

So, while it’s nice to think of toxoplasmosis as a condition that causes your cat to smell divine, that myth just isn’t true. It’s a much more nuanced condition that pet parents should be aware of—but shouldn’t panic over.  

In her practice, Dr. Cornelius has seen kittens with neurologic toxoplasmosis and some healthy cats that test positive on routine fecal screens. “With appropriate treatment and supportive care, all the outcomes have been good,” she says.