Parasite Alters the Brains of Wolves, Humans

We’ve known for some time that the Toxoplasma gondii parasite can infect the brains of rodents, forcing them via mind control into fatal encounters with predators. Now scientists have observed that wolves infected with T. gondii are also altering their behavior, in their case by taking more risks.

The parasite lives in many warm-blooded species, including humans, but its reproductive stage is spent exclusively in the viscera of cats, both wild and domestic. T. gondii doesn’t really harm the felines; on the contrary, it leads rats and mice right into their waiting claws, thus keeping the parasite's life cycle in motion.

The researchers pored over years of data on Yellowstone Park’s gray wolves and found that T. gondii-infected specimens were greater risk takers and more than twice as likely to become pack leaders as the uninfected. Just as rodents lose their instinctual fear of cats (to their peril), young wolves become more willing to explore and wander, perhaps to their benefit. The wolves pick up T. gondii from cougars in the park, probably by rooting around in the scat.

Wolf behavior is studied closely because they are a keystone species: whatever happens to wolves can disrupt the entire food web and make or break an ecosystem. It is unclear if the infection harms or helps the wolves’ cause in the wild.

As for humans, it is possible that three-quarters or more of the world’s eight billion are infected with T. gondii, and we’re only beginning to understand how it’s affecting our brains and behavior. Lotsa zombies out there.

The wolf study appears in the journal Nature Communications Biology.

Photo credit: National Park Service