Toxoplasmosis and psychology: a case of fatal feline attraction

Toxoplasma gondii is not an alien; it is a relative of that down-to-earth pathogen Plasmodium, the beast that causes malaria. It is common: in some parts of the world as much as 60% of the population is infected with it.

A country’s level of Toxoplasma infection seems to be related to the level of neuroticism displayed by its population. Another is that those infected seem to have poor reaction times and are more likely to be involved in road accidents.

Nor is any of this truly surprising. For, besides humans, Toxoplasma has two normal hosts: rodents and cats. And what it does to rodents is very odd indeed.

Fatal feline attraction

Joanne Webster of Imperial College, London, has been studying Toxoplasma for years. Like Plasmodium, which cycles between mosquitoes and man, Toxoplasma cycles between its rodent and feline hosts, living out different phases of its existence in each. In cats, it resides in the wall of the small intestine and passes out of the host in its faeces. These are then picked up by rats and mice (and also by other mammal species, including humans), where they form cysts in brain, liver and muscle tissue. Eventually, if the parasites are lucky, their rodent host is eaten by a cat and the whole cycle starts again.

Unlike Plasmodium, however, which can rely on the natural behaviour of mosquitoes to spread it around, Toxoplasma’s rodent hosts have a strong aversion to helping it into its next home. Which is where, in Dr Webster’s elegant phrase, fatal feline attraction comes in. Rats and mice infected with Toxoplasma start wandering around and drawing attention to themselves—in other words, behaving in ways that will bring them to the attention of cats. They are even, Dr Webster’s work suggests, attracted to the smell of cats.

Read the rest: Toxoplasmosis and psychology: A game of cat and mouse | The Economist.