Research led by Nanyang Technological University’s Dr Ajai Vyas and team shows that the parasite, Toxoplasma gondii, can dictate its hosts behavior. This parasite normally resides in cysts within the rat brain and causes the rat to become fearless, by altering their response to cat smells.
An earlier study had found that rats infected with the parasite produced extra amounts of the neurotransmitter called arginine vasopressin which is synthesized by a small set of neurons in the medial amygdala region which controls emotional responses. Hence, they hypothesized that in infected rats, the parasite may have activated the genes for arginine vasopressin production.
Experiments showed that, in infected rats, the methyl groups/molecular caps which silence the gene were missing, thereby causing an increase in the production of the neurotransmitter. This caused the rats to become fearless by making them lose their natural fear to feline odor. Ongoing experiments are studying the role of methylation and how Toxoplasma gondii might be exploiting it to control host behavior.
Full details of the discovery can be accessed here.