One much-appreciated feature of housecats is the readiness with which they poop in the same relatively easy-to-clean box day after day. However, cat owners should take care to change cat litter regularly and to wash their hands thoroughly after doing so. This is because cats (not just domesticated ones, but wilder felines like lions and tigers too) are the only known definitive hosts of the protozoan parasite Toxoplasma gondii.
Being a definitive host means the parasite, which in this case is spread through feces, can only sexually reproduce within a cat. But that doesn’t limit its infectivity to our kitty companions; it can also infect all kinds of other animals, including at least a third of the human population. “It infects almost all warm-blooded organisms,” says Ajai Vyas, an associate professor at Nanyang Technological University in Singapore and an expert in neuroscience and parasitology.
