Cat parasite makes infected mice generally less anxious
It’s been known for some years that when the cat parasite Toxoplasma gondii infects rodents it causes them to lose their fear of feline predators, making them easier to catch, and so allowing the parasite to complete its life cycle within cats.
However, according to new research carried out by a team at the University of Geneva, the effect of T. gondii is wider in reach and actually leads to infected mice showing a decrease in general anxiety and a reduced aversion to a broad range of threats – not just cats.
They found that mice infected with the parasite for at least five weeks
were more likely to explore novel environments, interact with the hands of the researchers, and investigate the odours of bobcats, foxes and guinea pigs than their more skittish, uninfected counterparts.
To investigate what was going on, the team used a cutting-edge imaging system
to accurately map the distribution, size and number of cysts caused by T. gondii in the brains of the infected mice. They found particularly high concentrations of cysts in regions involved with processing visual information, along with high levels of inflamed neural tissue throughout the brain.
“For 20 years, T. gondii has served as a textbook example for a parasitic adaptive manipulation, mainly because of the specificity of this manipulation said Prof Ivan Rodriguez, a co-senior author of the study. “We now show that the behavioural alteration does not only affect fear of feline predators but that major changes occur in the brain of infected mice, affecting various behaviours and neural function in general".
The researchers now plan to further examine how neuroinflammation can alter a range of behavioural traits such as anxiety, sociability or curiosity.