As many have been following the news of flesh-eating bacteria, there’s a new contender vying for top place as creepiest affliction: brain tapeworms.

Brain tapeworms are to blame for the most common parasitic disease of the nervous system, neurocysticercosis, which is the main cause of acquired epilepsy in developing countries, and surprisingly, is more common in the United States than you might think.

As covered in Discover Magazine this week, brain tapeworms are the larvae of adult tapeworms (Taenia solium). Before they become adults — reaching up to 20 feet long and taking residence in human intestines — tapeworms spend time as larvae in large cysts. And those cysts can end up nestled in the human brain.

In a complicated choreography of tapeworms, foraging pigs, larvae and undercooked pork — somehow tapeworms can take a wrong turn, and instead of ending up in a pig (their target host) the eggs end up in a human who has ingested them. As Discover describes it, “When the egg hatches, the confused larva does not develop into an adult in the human’s intestines. Instead, it acts as it would inside a pig. It burrows into the person’s bloodstream and gets swept through the body. Often those parasites end up in the brain, where they form cysts.”

Finding a hospitable environment inside fluid-filled cavities in the brain, they settle in and are masked from the immune system. These larvae can form vast networks on the brain and can wreak utter havoc if they’re not treated.

Dr. Theodore Nash, chief of the Gastrointestinal Parasites Section at the National Institutes of Health (NIH), cites side effects such as stupor, coma, loss of motor functions, violent seizures, blindness and even death.

Although clear figures are difficult to ascertain, Nash estimates that 2,000 people in the United States might have brain tapeworms. Global numbers are much higher, though estimates are difficult to assess because neurocysticercosis is most common in impoverished areas with poor public-health systems. Nash estimates that anywhere from 11 million to 29 million people have neurocysticercosis in Latin America alone.

There are drugs to treat the problem, but many of the treatments have debilitating side effects. Efforts can be made to prevent tapeworms from invading the human brain in the first place by finding and treating people who have adult tapeworms. It is also possible to vaccinate pigs against tapeworms.

“I see this as a disease that can be treated and prevented,” says Nash. Until then, make sure to thoroughly cook your pork and wash your hands and surfaces well after handling raw meat.

Related on MNN:

Brain tapeworms: More common than you thought
Brain tapeworms are more common than you might think. When pork tapeworm larvae take a wrong turn, they can end up in the human brain with devastating effects.