Toxoplasmosis in Cats and Pregnant Humans

I felt like I would be the poster child for Who Develops Toxoplasmosis

November 19, 2021 (published)
Photo courtesy of Depositphotos

Many years ago now, I had a pregnancy scare.  One of the standard tests run during my pregnancy came back as being abnormal.  As is typical in the human and veterinary medical fields, because this was a screening test an abnormal result meant more testing was ordered.  One of the concerns was for toxoplasmosis.  I’m a veterinarian.  At that time, I’d been practicing for about 10 years and had been in the field much longer.  I’d owned cats my whole life.  I felt like I would be the poster child for Who Develops Toxoplasmosis.  Thankfully, due to a lot of good hygiene and likely some luck, the tests came back negative.  I went on to have a healthy baby who has grown into a healthy teen.

So really, what is the risk of toxoplasmosis to pregnant humans?  And in particular, what is the risk of developing toxoplasmosis from your cat?

The short answer is that it’s really, really low. 

Cats become infected with Toxoplasma gondii, the organism that causes toxoplasmosis, from hunting and ingesting infected animals.  Therefore, indoor cats are much less likely to ever become infected in the first place.  If a cat is infected, it may shed the T. gondii oocytes (think “eggs” here) in their feces for a few weeks at most.  It is only during this time of the cat’s first infection where toxoplasmosis could be transmitted to a human.  But the timing is important, too.  Once the organism is shed in the feces, it takes 1-2 days to actually become infective.  Therefore, removing feces from the litterbox every 12-24 hours will not only make your cat happy, it will remove the oocytes before they reach a stage where they can infect a pregnant human.  Finally, the way a human becomes infected is by ingesting the organism.  In other words, something contaminated with T. gondii needs to make it into the mouth of the pregnant person.  Therefore, if a pregnant woman wears disposable gloves while cleaning the litterbox, or washes her hands after cleaning, or preferably both, then the risk of infection further decreases dramatically.

To summarize, for a pregnant woman to become infected with toxoplasmosis by her cat, the cat would need to become infected during the woman’s pregnancy and the woman would need to be cleaning the litterbox less frequently than every 24 hours and she would need to be doing it while not wearing gloves and/or washing her hands afterwards.  That’s a lot of requirements with impeccable timing.

So how would a pregnant person become infected with toxoplasmosis if it’s not the household cat?  Most infections likely occur from consuming raw or undercooked meat or milk, or eating unwashed fruits and vegetables.  Many others may occur from unwashed hands after gardening or other activities involving soil.  In fact, avoiding raw and undercooked meats and milk, washing fruits and vegetables before eating them, and washing hands after gardening (and before eating) are much more important ways to prevent transmission of toxoplasmosis to people than concerns about the family cat.

So keep the cat!  Wash your fruit, veggies, and hands!  And cook your meat fully!  Best of all, if it is possible, this is a great time to get someone else to clean the litterbox.  Just to be safe.


Toxoplasmosis in Cats, Veterinary Partner

Toxoplasmosis in Cats, Cornell University 

Zoonotic Disease: What Can I Catch from My Cat?, Cornell University 

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