In popular culture, fictional zombies are often depicted as mutant shells of their formerly human selves, with green-tinged skin, vacant eyes and an appetite for brains.
But did you know there are real-life organisms that can infect people and alter their behavior in ways that are reminiscent of zombies?
That's the focus of IU School of Medicine Professor Bill Sullivan, PhD, and his research lab, which studies Toxoplasma gondii, the causative agent of toxoplasmosis. This is a single-celled parasite that makes its eggs (oocysts) in the gut of cats. Infected cats expel these parasitic eggs into the environment, contaminating the soil, gardens, and fruits and vegetables.
Sullivan said the parasite can infect any animal, including humans, forming tissue cysts in their organs and muscles. Eating undercooked meat infected with the parasite is another common way to catch toxoplasmosis. The parasite can also be transferred from mother to unborn child.
"After a host is infected, the parasite forms cysts throughout the body, including the brain," Sullivan said. "These cysts, which cannot be eradicated by known drugs, persist for the host's life and have been linked to spooky behavioral changes, doing things they normally wouldn't do."
Infected mammals commonly show greater risk-taking behavior, leading some to dub Toxoplasma a zombie parasite. And much like zombies, this disease may influence our decision-making abilities.
If you're wondering how these ghastly cysts can invade the human body, here's a closer look at how they can transform our insides into a "zombie zone."
- Toxoplasma uses multiple routes of transmission.
- Feline species expel the parasite's eggs into the environment.
- Toxoplasma infects all warm-blooded animals such as sheep, pigs and cattle.
- Up to 3 billion people worldwide are infected.
- Once you are infected it is lifelong; there is no cure.
- People with Toxoplasma have 1.9 times greater risk of developing schizophrenia.
- People who own cats have 2 times greater risk of developing schizophrenia.
- Some studies suggest that people infected with Toxoplasma are more likely to engage in risky behavior, more prone to rage disorder, and more likely to be involved in car accidents.
But have no fear — Sullivan, the Showalter Professor of Pharmacology and Toxicology and a professor of microbiology and immunology, along with his research lab identified a way to possibly avert a zombie apocalypse by treating toxoplasmosis.
An old, FDA-approved blood pressure medication called guanabenz was found to greatly reduce Toxoplasma cysts in the brain of infected mice and reverse the behavioral changes. Once treated, the parasites inside of the cysts begin to shrivel away and die.
Sullivan's ongoing research aims to better understand how Toxoplasma "zombifies" its host and how we might be able to stop the process and clear the parasite from the body.
