Here’s what you already know: it’s a parasite that reproduces in the digestive system of cats. The eggs are excreted out and the vehicle is consumed by other animals in whose brains the eggs develop. Only when those brains are consumed by other cats does the cycle continue. In order to facilitate this process, chemicals are secreted inside the hosts’ brain to make them do things to increase the chance they will be eaten by cats. For example, rats with toxoplasma in their brains are not afraid of cats.
Here’s what’s new: toxoplasma is transferred from host to host through sexual contact in order to get closer to cats.
These are Toxoplasma cysts moving from rat to rat, so this exchange is kind of like a side track on the parasite’s life cycle. But it still benefits Toxoplasma, because it means it can infect even more potential prey that may get eaten by cats. And so the logic applies once more: if Toxoplasma can raise the odds of getting from infected males to uninfected females, it may have more reproductive success.
You know where this is going–it’s turning into a David Cronenberg horror movie with an all-rodent cast. Vyas wondered if there’s any difference in how female rats mate with infected and uninfected males. So he and his colleagues put a male rat with Toxoplasma at one end of a two-armed maze, and an uninfected male in the other arm. Females then got to choose which rat to approach. Vyans found that they preferred the infected males, spending more time with them and mating more often.