"It's a remarkably complex parasite. It's much more complicated than a virus, and has many more genes," Torrey said. The microbe is famously known to infect rats and change their behavior, causing them to be less afraid of the smell of cat urine. This makes it easier for the rats to be eaten by cats, returning the parasite to its host.
Treatments do exist, but none are very effective, Torrey said. Most people don't have long-term effects, but it's not clear why some do. Genetic predisposition or age at the time of infection could play a role, Torrey said.
More research is needed to understand the risks posed by the Toxoplasma parasite. In the meantime, Torrey advocated controlling cat populations, especially feral ones. Children's sandboxes should be covered. Gardeners should wear gloves and wash their vegetables. And cat owners should dispose of cat litter properly - in the trash, not down a toilet (and pregnant women shouldn't change it at all).
"None of us are saying cats shouldn't be pets," Torrey said, but "there are some downsides to all pets, and some downsides to cats we should be aware of."