Is it bollocks?

Film Buff investigates the facts behind outlandish movie plots.

Could a psychotic parasite control you, as in Venom?

This Month Venom’s psychotic parasite

QIn Venom, Tom Hardy’s journo gets infected with an alien parasite that turns him into a marauding head-chomper. Are there real parasites that can change your personality?

ASEPEEDEH SALEH MBCHB, MPH, MFPH, THE LIVERPOOL SCHOOL OF TROPICAL MEDICINE In terms of parasites that cause changes in behaviour in humans, the one that first springs to mind is African trypanosomiasis, aka sleeping sickness. This is caused by trypanosoma parasites and spread by the bites of tsetse flies. The parasites enter the system, causing fever, then get into the nervous system, where they start to affect the brain. As well as more typical psychiatric symptoms such as delusions, affected patients also commonly show changes in their behaviour, becoming uncharacteristically rude and aggressive, or careless.

A similar reaction is seen in toxoplasmosis – a disease caused by a parasite (toxoplasma) that lives in various mammals. Toxoplasma can also infect humans, although it doesn’t cause any disease in most people. When carried by a mouse, it affects its host’s behaviour, changing its normal fear of predators (such as cats) to an attraction. It has been proposed that this risk-taking behaviour change also happens in infected humans, making them more likely to be involved in road traffic accidents, for instance, but this has not been proven.