Source: Michael Fielding, MEATINGPLACE, 6/13/16

A University of California, Riverside team of biomedical scientists reported in a recent journal article in PLOS Pathogens that toxoplasma infection leads to a disruption of neurotransmitters in the brain. They postulate that it triggers neurological disease in those already predisposed to such a disease.

Ingested via undercooked meat or unwashed vegetables, the parasite infects a third of the world's population (it infects 15 percent to 30 percent of the American population).

The chronic infection has two components: the unicellular parasite and inflammation of tissues it causes.

The researchers noted that toxoplasma infection leads to a significant increase in glutamate – the primary and most important neurotransmitter in the brain, which transmits excitatory signals between neurons. This glutamate increase is "extracellular," meaning outside the cell, and is strictly controlled by specialized cells in the central nervous system (brain and spinal cord), called astrocytes.

Glutamate buildup is seen in traumatic brain injury as well as highly pathological and neurodegenerating diseases such as epilepsy, multiple sclerosis and amyotrophic lateral sclerosis (ALS).

"When a neuron fires it releases glutamate into the space between itself and a nearby neuron," explained lead researcher Emma H. Wilson, an associate professor in the Division of Biomedical Sciences in the School of Medicine, who has worked on toxoplasmosis for more than 15 years. "The nearby neuron detects this glutamate which triggers a firing of the neuron. If the glutamate isn't cleared by GLT-1 then the neurons can't fire properly the next time and they start to die."

Wilson and her team found that during toxoplasma infection, astrocytes swell and are not able to regulate extracellular glutamate concentrations. Further, GLT-1 is not expressed properly. This leads to a buildup of the glutamate released from neurons and the neurons misfire.

The parasite is not as latent or dormant as researchers once thought. Cases of congenital infection and retinal toxoplasmosis are on the rise (the brain and retina are closely linked). People who have schizophrenia are more likely to be infected with toxoplasma. Infection shows some correlation with Alzheimer's disease, Parkinson's disease and epilepsy.

Nevertheless, Wilson noted that infection is no cause for major worry.

"We have been living with this parasite for a long time," she said. "It does not want to kill its host and lose its home. The best way to prevent infection is to cook your meat and wash your hands and vegetables. And if you are pregnant, don't change the cat litter."

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