All it takes is one exposure, and your "indoor" cat can infect your remaining pets (and you).
This entire topic is is marred with silly nonsense like "your only risk is mishandling cat feces", which totally ignores things like:
1) The cat litter box is covered in microscopic parasite-containing cat feces
2) The cat tracks feces-covered litter out of the box into the living space, which further spreads the parasite. If you walk barefoot through your house, you will step on cat liter pieces eventually which are again covered in microscopic feces.
3) The cat steps in litter covered in cat feces from other cats, gets it on its paws, which it then licks, starting the infection cycle over again. Multiple cats can easily keep a perpetual infection cycle going.
4) Cats, even well trained ones, routinely climb on top of furniture/eating/cooking surface and coat them in their feces. My parents were shocked after installing an interior camera when they saw their "well-behaved cats that never do that" walk all over their dinner table, kitchen counters, open and go inside cabinets etc etc. They are smart enough to know when you are around or not, and to not act like this when you can see them.
5) Cats have sharp claws, and even well behaved ones can accidentally scratch you or scratch a toddler that gets too close etc. This will then directly introduce cat feces to your blood stream.
Once exposed, the initial symptoms are mild flu-like symptoms and not a huge deal (unless you are pregnant, in which you will likely experience a miscarriage. Pregnant women should not be exposed to cats, or be in a household that has indoor cats). The real issue is the long term cysts they leave behind in your brain, causing a latent inflammation and immune response that seemingly interacts with your dopamine system in poorly understood ways. For example, latent cyst-stage toxoplasmosis significantly increases your risk of developing schizophrenia.