Toxoplasmosis is a parasitic disease caused by infections of the protozoan parasite Toxoplasma gondii.
It is extremely widespread in the human population. Infection rates vary in various regions of the world - but it's currently estimated that about 40 - 60% of the human population permanently hosts the parasite.
The parasite itself was first identified in 1908, and the first case of Toxoplasmosis in 1940.The organism and the infection routes are very well understood. Evidence of infection has now been found in almost all warm-blooded animals. Cats are the known to be the main host.
It usually causes no physical symptoms in those infected - other than a short flu-like episode in some individuals. However, in the early 2000s it was noted suggested that the parasite may also have a psychological effect on those infected.
It has now been linked to changes in brain dopamine levels (up to 15%) and can lead to so-called 'aberrant' behaviour - which to date has been verified in rats, otters and cats.
The mechanism of action that the parasite appears to have in altering brain chemistry is unknown.
It is currently suggested that it may have an influence on the prevalence ofand
Bearing in mind that half the human population may be infected, some researchers have suggested that it may even be having an effect at the 'societal' level.
Can the common brain parasite, Toxoplasma gondii, influence human culture? Proc Biol Sci 2006 Nov 7;273(1602):2749-55
Further info Wikipedia