In collaboration with Bob Yolken of Johns Hopkins University, Dr Fuller discovered that people who suffer from schizophrenia are almost three times more likely than the general population to have antibodies to Toxoplasma.

ECONOMIST: Toxoplasmosis and psychology

Or take Toxoplasma, a protozoan that needs to move between cats and their prey and back again in order to complete its life cycle.

FORBES: Those Resourceful Bugs

Toxoplasma can also infect the human brain, making men distrustful of others and less likely to heed moral rules.

FORBES: Those Resourceful Bugs