Common parasite linked to epilepsy and other brain disorders

Posted Sep 15 2017 in Brain science; genetics

Toxoplasma gondii (T. gondii) is a very common parasite that is often associated with cats and is thought to cause very few symptoms and no serious effects in humans. However, research led by the University of Chicago has now shown that it might, in fact, play a role in the development of epilepsy and other brain disorders. The findings are published in the journal Scientific Reports.

T. gondii is able to live in the brain cells of nearly all warm-blooded animals. Evidence shows that 30-50% of the world population is infected with T. gondii, but most people aren’t aware of it. Occasionally, however, it causes a condition called toxoplasmosis, and if a woman is infected before or during pregnancy, the parasite can, in rare cases, seriously harm the brain and eyes of the developing child.

There are a number of ways in which humans can become infected with T. gondii, for example by eating uncooked food; inadvertently swallowing infected soil (from the  feces of infected aimals); and eating raw, unwashed vegetables. Cats are the only known animals in which T. gondii can sexually reproduce, and they (young kittens especially) play an important part in the spread of the parasite. This is why pregnant women are advised not to clean cat litter trays.

The latest study, which involved 32 scientists across 16 institutions, used a database containing information about 246 people who had become infected with T. gondii in the womb. The team searched for parasite-generated signs (known as biomarkers) that were not present in an unaffected group of people and examined their probable impact on health.

The search revealed a significant link between T. gondii  infection and the presence of small (non-coding) human RNA molecules known as microRNA. It also showed that parasite-associated microRNA, along with proteins produced by T. gondii, were present, not only in children with severe toxoplasmosis, but also in adults with Parkinson’s disease and Alzheimer’s disease.

In addition, the researchers found evidence that T.gondii proteins can disrupt GABA signalling, thus disturbing the balance between excitation and inhibition in the brain and increasing the risk of epileptic seizures.

Lead Investigator, Dr Rima McLeod, says:

“We suspect it involves multiple factors.

“At the core is alignment of characteristics of the parasite itself, the genes it expresses in the infected brain, susceptibility genes that could limit the host’s [infected person’s] ability to prevent infection, and genes that control susceptibility to other diseases [including epilepsy] present in the human host.”

You can read about the harmful effects of T. gondii  in other animals here.

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