Parasite Influences Behavior

This dendritic cell is infected by Toxoplasma gondii (in red). Copyright: A. Barragan

Researchers from the Karolinska Institutet medical university in Sweden have discovered how a parasite that is commonly seen in domesticated cats can infect the human brain and influence behavior. The parasite, Toxoplasma gondii, is estimated to infect as much as half the global population. It causes the disease toxoplasmosis which is commonly contracted by eating undercooked meat from infected animals or by handling cat feces. Toxoplasmosis generally causes flu-like symptoms, but most infected individuals do not experience illness as the immune system keeps the parasite in check. In some cases however, toxoplasmosis can be deadly for those with compromised immune systems. Mental disorders are also seen in those with this disease.

According to researcher, Dr. Antonio Barragan, "We've shown for the first time how the parasite behaves in the body of its host, by which I mean how it enters the brain and manipulates the host by taking over one of the brain's neurotransmitters." In humans, Toxoplasma gondii commonly infects body tissues such as skeletal muscle, heart muscle, and eye and brain tissue. In the study, immune cells known as dendritic cells were infected with the parasite. The dendritic cells began to secrete the signaling substance GABA which is known to influence fear and anxiety related behaviors. Individuals with toxoplasmosis sometimes experience mental diseases such as schizophrenia, depression, bipolar disorder, and anxiety syndrome.

Learn more about this study, see:

• How Common 'Cat Parasite' Gets Into Human Brain and Influences Human Behavior (Science Daily)