March 11, 2009 — Scientists have discovered
how the toxoplasmosis parasite may trigger the development of
schizophrenia and other bipolar disorders.
The team from the University of Leeds’ Faculty of Biological
Sciences has shown that the parasite may play a role in the development
of these disorders by affecting the production of dopamine — the
chemical that relays messages in the brain controlling aspects of
movement, cognition and behaviour.
Toxoplasmosis, which is transmitted via cat faeces (found on
unwashed vegetables) and raw or undercooked infected meat, is
relatively common, with 10-20% of the UK population and 22% of the US
population estimated to carry the parasite as cysts. Most people with
the parasite are healthy, but for those who are immune-suppressed —
and particularly for pregnant women — there are significant health
risks that can occasionally be fatal.
Dr Glenn McConkey, lead researcher on the project, says:
“Toxoplasmosis changes some of the chemical messages in the brain, and
these changes can have an enormous effect on behaviour. Studies have
shown there is a direct statistical link between incidences of
schizophrenia and toxoplasmosis infection and our study is the first
step in discovering why there is this link.”
The parasite infects the brain by forming a cyst within its cells
and produces an enzyme called tyrosine hydroxylase, which is needed to
make dopamine. Dopamine’s role in mood, sociability, attention,
motivation and sleep patterns are well documented and schizophrenia has
long been associated with dopamine, which is the target of all
schizophrenia drugs on the market.
The team has recently received $250,000 (£160,000) to progress its
research from the US-based Stanley Medical Research Institute, which
focuses on mental health conditions and has a particular emphasis on
Dr McConkey says: “It’s highly unlikely that we will find one
definitive trigger for schizophrenia as there are many factors
involved, but our studies will provide a clue to how toxoplasmosis
infection – which is more common than you might think – can impact on
the development of the condition in some individuals.
“In addition, the ability of the parasite to make dopamine implies a
potential link with other neurological conditions such as Parkinson’s
Disease, Tourette’s syndrome and attention deficit disorders, says Dr
McConkey. “We’d like to extend our research to look at this possibility
Source : University of Leeds