Parasites shown to control mice behavior.
Researchers from the University of California, Berkeley suggest that mind-altering parasites are not such a far-fetched idea.
The researchers set out to test the validity of claims concerning the parasite Toxoplasma gondii that could alter the natural instincts of rodents. Previous studies suggested that the parasite could only complete its life cycle from within a feline gut. Researchers hypothesized that rodents affected with Toxoplasma gondii would lose their fear of feline predators to complete the life cycle of the parasite.
The researchers tested this hypothesis using all three known strains of the parasite. In this study, the researchers found that the second strain was not a good example of the parasite. The surviving mice that were infected with the often-lethal strain were extremely ill as a result. Their movements were limited—something the study looked to measure.
For the experiment, a cage was set up with a bowl on one end that would contain either rabbit or bobcat urine. The healthy mice had a strong aversion to the bobcat urine and spent the majority of their time during the study in what was called the ‘avoidance area’ at the opposite end of the cage. When placed in a cage with the rabbit urine, they freely roamed around. Like the healthy mice, the infected mice paid no attention to the rabbit urine. However, when the infected mice were placed in a cage with the bobcat urine, they showed no aversion. This shows that the infected mice had lost their natural fear of feline urine.
There are three different strains of the Toxoplasma gondii. This experiment looked at the effects of specifically the first and third strain. Those two strains caused the same loss of natural avoidance instinct in the mice. However, during the biopsy of the mice’s brains, the researchers found something interesting: in the mice that were infected with the third strain, they had found an elevated parasite level, while the mice that were infected with the first strain had no detectable parasite levels.
After further investigation, the scientists determined that the parasite levels in the first strain spike and then die off. Despite the parasites dying off, the effects are long lasting. This particular strain was shown to be able to permanently change the mind of its host.