September 30, 2003
Humans Get Personality Altering Infections From Cats

Professor Jaroslav Flegr of Charles University in Prague has discovered evidence that infection by intracellular protozoan parasite toxoplasma gondii (T. gondii) causes changes in human personalities.

He found the women infected with toxoplasma spent more money on clothes and were consistently rated as more attractive. “We found they were more easy-going, more warm-hearted, had more friends and cared more about how they looked,” he said. “However, they were also less trustworthy and had more relationships with men.”

By contrast, the infected men appeared to suffer from the “alley cat” effect: becoming less well groomed undesirable loners who were more willing to fight. They were more likely to be suspicious and jealous. “They tended to dislike following rules,” Flegr said.

Why the cat parallels? The parasite infects cats and is passed on to rats by cat feces. In rats it creates the proverbial fatal attraction.

T. gondii makes rats more susceptible to being caught by cats.

LONDON - Scientists have discovered a parasite that inhabits rats and makes them feel a suicidal attraction for cats. The parasite, which infects as many as one in five rats, can also affect humans.

The parasite, nicknamed the love bug but scientifically known as Toxoplasma gondii, an intracellular protozoan, infects the rodent's brain, inducing an effect similar to Prozac so it becomes less fearful of cats.

It might be too late to get rid of Fluffy. U College London T. gondii researcher Dr Dominique Soldati says once infected you have it for life and it gradually grows.

“Once you are infected you cannot get rid of this parasite and the numbers of them slowly grow over the years,” she said. “It’s not a nice thought.”

The parasite apparently evolved to help cats eat rats.

The scientists set up a wild enclosure for rats, with different smells in each corner. Rats infected by the parasite were attracted to the smell of cat urine.

The minds of infected rats are subtly altered so that they become less able to avoid getting captured and eaten by cats. Cat feces that are eaten by rats serve as a way to spread the disease to rats that the cats can then eventually capture and eat.

As this review of the molecular biology of T. gondii demonstrate scientists are looking for ways to stop and destroy this parasite once it has infected humans.

T. gondii has evolved a remarkable ability to survive in its host, typically for long periods of time, with minimal pathogenicity and in a variety of cell types. However, the mechanisms by which this obligate intracellular parasite becomes a master at manipulating the structures and pathways of the host cell for its own nefarious purposes to create a hospitable environment remain difficult to analyse in the background of a nucleated host cell.

T. gondii infection is especially dangerous for children born to women who become infected during pregnancy.

Toxoplasma, mainly transmitted by consumption of contaminated meat or by cat faeces, chronically infects half the world's population. The pathogen is a leading cause of neurological birth defects in children born to mothers who contract the disease during pregnancy and can cause fatal toxoplasmosis encephalitis in immunosuppressed patients.

Scientists hope that understanding the gene's function will aid efforts to develop drugs that target and block the way Apicomplexa parasites penetrate host cells.

Women who want to have children should probably give away Fluffy to post-menopausal women who show signs of promiscuity and large tasteful wardrobes.

But what about the threat to Western Civilization? Cats are making our women less trusthworthy and more superficial while they are making men into scruffy loners who are unwilling to follow rules. If some terrorist group was releasing pathogens that had this effect we'd be hunting them down and killing them without mercy (assuming the FBI and CIA could find them - the anthrax mail case may never be solved). But since kitties are fluffy, make cute purring sounds, and occasionally rub up against people's legs they are considered adorable by many. This leaves them free to operate in plain sight to undermine Western Civilization while every single one of them affects an air of total indifference and disinterest.

Update: Christopher Genovese has taken the time to read some of Jaroslav Flegr's research papers and presents an excellent analysis on the question whether Flegr's work has discovered a real effect on humans. My take on it is that while it isn't clear that Flegr has proved his case it is plausible in part because the human domestication of cats happened fairly recently (in ancient Egypt if memory serves) in human evolution. So a deleterious effect on humans of a cat parasite seems like something humans wouldn't have had time to evolve to develop an effective response. By contrast, the likelihood of getting harmful parasites from dogs would seem lower since humans have been living with dogs for a much longer period of time.

Share |      Randall Parker, 2003 September 30 04:28 PM  Biological Mind

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