(Not) Scaredy Rat

Toxoplasma gondiiis a dangerous bug (technically protozoan) to catch. It has been associated with everything from traffic accidents to schizophrenia in humans, but this is nothing compared to what it does to rodents. When it infects rodents it makes them brave. Suicidally brave. For over twenty years, scientists have been researching how this infection causes rodents to lose their fear of cats. When infected rodents don’t run away from their natural predators, they get eaten, allowing for the bug to spread into the cat’s gut and complete its lifecycle.

New research from the University of California has shown that the power of Toxoplasma gondii is even worse for rodents than originally thought. Previously, it had been assumed that even if a rodent was infected, if it was lucky enough to avoid any cats for long enough the bugs would die off. And that the rat would then regain its instinct for self-preservation. However the new research published in PLOS ONE showed that this was not the case.

In the study, scientists tested mouse-fear by seeing how infected and uninfected mice reacted to different types of urine. The mice were put into cages which had dishes filled with either rabbit urine or cat urine. As expected, neither the infected or uninfected mice reacted at all to the rabbit urine and moved freely around the cage.

The uninfected mice, however, showed extreme fear towards the cat urine and stayed at the opposite end of the cage, as far away from it as they could possibly be. Meanwhile the infected mice treated the cat urine the same as the rabbit urine and moved about freely. The surprising result was that the infected mice continued to ignore the cat urine for four months after the infection had cleared (the study stopped at four months). This suggests that the infection made permanent changes to the brains of the mice.

Next time you’re feeling scared about something, whether you’re going skydiving or asking out that cutie from your tutorial, consider infecting yourself with Toxoplasma gondii. But beware: the effects will probably be permanent.

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