Explosive road rage-like anger linked to parasite spread by cats
There are many ways your cat might be filling you with rage:
- Scratching your furniture
- sitting on your computer keyboard
- or giving you parasites that may cause explosive anger.
Infection with Toxoplasma gondii, a protozoan parasite carried by cats
- has been linked to a human psychiatric condition called intermittent explosive disorder.
- People who have IED typically experience disproportionate outbursts of aggression, like road rage.
- T. gondii is already known to change the behaviour of the organisms it infects.
- By making rodents bolder and more adventurous, the parasite makes them more likely to be caught and eaten by a cat,
- allowing the parasite to complete its life cycle.
It can also infect humans
- through contact with cat faeces, poorly cooked meat or contaminated water
- as many as 33% of the world’s population may be infected
- The protozoan doesn’t make us feel sick, but forms cysts in the brain
- where it can remain for the rest of a person’s life.
- Such infections have been linked to psychiatric conditions including:
- schizophrenia, bipolar disorder & suicidal behaviour.
- People infected with T. gondii also have slower reaction times &
- are more likely to be involved in car accidents.
To see if T. gondii is associated with aggression
- Emil Coccaro at the University of Chicago and his colleagues examined 358 adults
- These fell into 3 groups:
--- people with IED,
--- people with other psychiatric conditions, and
--- controls, who had not been diagnosed with any psychiatric condition.
- They found that people with IED were more than twice as likely to test positive for exposure to T. gondii as the control group.
- Those with other conditions were also more likely to have the parasite.
- Across all 3 groups, those who tested positive tended to rank more highly in tests measuring aggression.
Coccaro thinks the parasite may boost aggression by altering neurotransmitters in the brain
- either by overstimulating neurons in the amygdala, the part of the brain that controls response to threats, or
- by impairing one of the forebrain’s functions – as a braking mechanism on such behaviour.
- “The findings make sense,” says Paul Ewald, an evolutionary biologist at the University of Louisville in Kentucky.
- “A mouse that is preoccupied with attacks on another mouse may be easy prey for a cat.”
- In this way, enhancing aggression could help spread T. gondii.
But Coccaro also says his evidence only shows a correlation between infection and aggression
- T. gondii doesn’t necessarily cause the explosive rage.
- It’s possible that aggressive people are more likely to catch the parasite,
- because they may be less likely to fully cook their meat or to wash their hands.
- One way to test the link would be to treat the infection in the people with IED, who tested positive for the parasite,
- and see if it has any effect on their behaviour.
- The only problem is that treatment can take a long time.
- “These parasites are so bloody difficult to kill,” says Coccaro
Journal reference: Journal of Clinical Psychiatry, DOI: 10.4088/JCP.14m09621
Bonus: The cat made me do it: Is your pet messing with your mind? (https://www.newscientist.com/article/mg22630230-200-the-cat-made-me-do-it-is-your-pet-messing-with-your-mind/)