Any warm-blooded animal, including humans, can become infected by ingesting oocysts from contaminated food or water sources, or even by inhaling them in dry areas where they have become aerosolized.  But none of these other warm-blooded animals can shed more oocysts.  These oocysts are microscopic.  Many, many of them could fit under your fingernail.  You don't have to do around spooning cat poop into your mouth to become infected.  A simple swipe of your hand across your sweaty brow after gardening is all it takes.

Humans and animals can also become infected by eating the undercooked meat of infected animals.  But those infected meat animals became infected by ingesting oocysts shed by cats.  No matter how humans or animals become infected, the original source is always cats.