Gina Guirguis never liked cats before she was given Bella, a fluffy black Himalayan Mountain cat, for her birthday five years ago.
“I think a lot of people don’t like cats until they have one,” said Ms Guirguis, who is now smitten.
But there could be a more sinister reason some people are attracted to the purring feline: a parasite in cats that could alter a person’s personality if they catch it.
According to infectious disease expert Kevin Lafferty, the parasite Toxoplasma gondii could make infected women kinder and infected men less intelligent.
Scientists first discovered that toxoplasma could alter behaviour in rodents, Dr Lafferty said.
Once an animal becomes infected, the parasite makes its way to the brain where it provokes the immune system, causing a series of chemical events that alter the level of dopamine in the brain.
Studies showed that rats infected with the parasite were more active and less fearful of cats.
Although this behaviour sounds strangely suicidal, Dr Lafferty said it was fuelled by the parasite’s need to survive.
While the parasite can live outside the body of a cat, it can mate and reproduce only inside the intestines of felines.
So by altering a rat’s behaviour, the parasite was trying to increase the chances it would be eaten by a cat so it could complete its life cycle, said Dr Lafferty, who works at the US Geological Survey.
Dr Lafferty believes when the parasite infects a human it uses the same tricks – including altering the levels of dopamine in the brain: “We know that changes in dopamine can have pretty significant effects on the behaviour of humans and other vertebrates.”
Parasitologist Dr Nicky Boulter, who studied Toxoplasma gondii for five years, said although it was clear that infected rats were drawn to cats, the science hadn’t proven this was why some humans were attracted to them.
But she said research over the past decade had shown the influence the parasite could have on human behaviour.
When women infected with the parasite were given an IQ test, researchers found they were smarter and more conforming than non-infected females. The same tests revealed that infected men were less intelligent and prone to novelty-seeking behaviour.
But these personality changes were often fairly subtle, said Dr Boulter, who works for a private genetics company.
When humans become infected with the parasite they often experience flu-like symptoms. Dr Lafferty said if the condition was not treated, the parasite could remain in the body for life.
The most common source of the parasite was eating undercooked meat, followed by exposure to contaminated soil and cats, he said.
The number of people infected with the parasite, which prefers humid, low-altitude regions, varies from country to country.
While more than 60 per cent of women of child-bearing age in Brazil are infected, only 6 per cent of their Norwegian counterparts are infected.
Close to 30 per cent of Australian women of child-bearing age are infected with the parasite.
What a lovely thought. I prefer to think I like them because they’re beautiful, independent creatures.
