Boffins here in Blighty say that a brain parasite which is carried by up to 20 per cent of the population is capable of affecting its host's actions for its own benefit – but against the interests of the host.
The parasite in question, Toxoplasma gondii, has now been found to "directly affect" the production of dopamine, a key chemical messenger in the human brain. Dopamine levels are implicated in human illnesses such as attention deficit hyperactivity disorder, Parkinson's disease and schizophrenia.
Toxoplasma gondii's primary host organism is cats, but it can also live in other creatures including humans and rats. Humans are infected with it by eating unwashed vegetables with cat poo on them:it's estimated that between 10 and 20 per cent of Brits carry the protozoan parasite and perhaps 22 per cent of Americans. Normally the hidden brain invader appears to have little effect on a human host,though it can kill in certain cases – for instance in the case of someone whose immune system isn't working.
Dopamine is a natural chemical which relays messages in the brain controlling aspects of movement, cognition and behaviour. It helps control the brain's reward and pleasure centres and regulates emotional responses such as fear. The presence of a certain kind of dopamine receptor is also associated with sensation-seeking, whereas dopamine deficiency in humans results in Parkinson's disease.
"Based on these analyses, it was clear that T gondii canorchestrate a significant increase in dopamine production in neural cells," says Dr Glenn McConkey of the Leeds' Faculty of Biological Sciences.
By Lewis Page
Source:http://www.theregister.co.uk/2011/11/07/brain_manipulating_parasite/