It was just another day for Zhu (alias name), a 64-year-old construction worker from the eastern Zhejiang province of China. While returning from work, he bought meat for his spicy hot pot broth, a dish enjoyed with fresh meat cuts being cooked in the hot boiling broth and eaten immediately. It wasn’t until days later that Zhu started experiencing headaches and epilepsy-like symptoms such as limb-twitching, mouth foaming, etc. Witnessing the symptoms, his co-workers encouraged Zhu to get medical help. At the hospital he went through multiple tests and scans which revealed abnormal deposits of calcium in his brain blood vessels. Even though the doctors wanted to explore further, he was reluctant, but he eventually gave in when the symptoms persisted. An MRI confirmed what the doctors feared. The concerning headaches, twitching-limbs and mouth foaming were all caused by Tapeworms! The tapeworm larvae from the meat cuts had survived because they were not cooked properly. This 2019 case study done by the First Affiliated Hospital of Zhejiang University is not the only bizarre case of brain parasites. Many people across the world have experienced them; who never thought their generic symptoms were due to an uninvited guest living in their brains. But these brain worms can do a lot more than trigger physical symptoms. When Change In Behavior Is Not A Surface-Level Problem To understand the different aspects of brain parasites and how they can affect the human mind, we spoke to Mr. Abhijeet Satani, Neuroscientist and Dr Srikanth, Consultant Neurologist at Apollo Hospitals. Usually when we feel irritable or forgetful, we chalk it up to stress and lack of sleep. However, have you ever considered the possibility of a parasite living in your brain? Mr. Satani explains that even though it sounds like fiction, neurocysticercosis is a real condition caused by tapeworms that infect the brain. Dr Srikanth adds to the fact, explaining that these worms can not only alter the behavior but could also be responsible for seizures, cognitive decline, mood changes, or even psychosis in severe cases. “This typically happens when someone ingests contaminated food or water with microscopic tapeworm eggs, often due to poor hygiene.” said Mr. Satani, “Once the parasite reaches the brain, it forms cysts, disrupting normal function. Symptoms can be complex and varied, including seizures, behavioral changes, mood swings, anxiety, or confusion. Some patients are misdiagnosed with depression or schizophrenia, only to discover later that a parasite is causing brain inflammation.” How Do "Brain Worms" Get Inside Us? The most common way people get infected with these brain worms is by accidentally consuming microscopic tapeworm eggs. These eggs are often found in contaminated food or water, typically due to poor hygiene. It might surprise you, unlike what many people believe, but you don't have to eat undercooked pork to get infected. Dr. Srikanth said, “Surprisingly, even vegetarians can get infected through salads or vegetables handled by someone with poor hand hygiene carrying tapeworm eggs.” This means even people who have been lifelong vegetarians can get this condition if they come into contact with contaminated food or water. It's not about the meat you eat, but what your food has been exposed to. Least Expected Way of Arrival However, one of the least expected ways one could get infected is from another person. Mr. Satani explained “If someone is carrying the adult tapeworm in their intestines, they can shed eggs through their feces. And if they don’t wash their hands properly, those microscopic eggs can spread to other people. I've seen cases where someone who doesn’t eat meat, doesn’t travel, and lives a relatively healthy lifestyle ends up with brain cysts simply because they were unknowingly exposed through contact. Something as routine as sharing food, touching a contaminated surface, or even eating in a local restaurant with poor hygiene standards could be enough.” Once these eggs are ingested, they hatch in the stomach. The larvae then travel through the bloodstream, and can eventually reach the brain, where they form cysts. These cysts then disrupt normal brain function. How Can Parasites Change Our Behavior? Some parasites have been shown to change how animals behave, and we're seeing similar patterns in humans. Mr. Satani explained that with "brain worms," changes in behavior usually come from the physical disruption and swelling caused by the cysts in specific parts of the brain. “I’ll never forget a man in his late 30s who was being treated for what doctors thought was bipolar disorder. He had episodes of paranoia, sudden anger, and intense mood swings. Medications weren’t helping much, and his family was confused and distressed. Eventually, someone suggested getting a brain scan, and to everyone’s surprise, the MRI showed multiple cysts in his brain. He was diagnosed with neurocysticercosis. After proper treatment, including antiparasitic drugs and steroids, his behaviour started to stabilise. He went from being considered a psychiatric patient to someone dealing with a treatable brain infection.”- Abhijeet Satani, Neuroscientist and Inventor of Cognitively Operated Systems . Dr. Srikanth adds that these changes can range from mood disorders to seizures, depending on where the cyst is located. Mr. Satani gave an example, if a cyst forms in the frontal lobe, which is the part of the brain that controls judgment, making decisions, and your personality, it can lead to sudden anger, impulsive actions, or emotional ups and downs. People might become unusually irritable, withdrawn, or paranoid, and it turns out to be due to pressure or swelling in the brain caused by a parasite. These aren't just mental issues; they are real physical changes. Some common changes observed are: Forgetting thingsTrouble focusingAnxietyDepressionHallucinationsHow Soon Do Symptoms Appear? Behavioral changes are usually not immediate. Most people don't even realize they're infected until the cysts start affecting how their brain works explained Mr. Satani. This can take anywhere from a few weeks to several months. At first, symptoms might be so small they're ignored—like being a bit more forgetful, anxious, or moody. But over time, especially if more cysts develop or swelling increases, the symptoms become harder to ignore. In some cases, seizures are the first big sign that something serious is wrong. Dr. Srikanth added another disturbing detail, “Some brain worms can survive for up to two decades, either remaining active or eventually calcifying and becoming dormant.” Mr Satani explains that our immune system doesn't always get rid of them on its own. In fact, the swelling caused by our immune system trying to fight them can sometimes do more damage than the cyst itself. That's why medical treatment usually involves both medicine to kill the parasite and steroids to reduce the swelling at the same time. Awareness and Early Detection The good news is that neurocysticercosis can be treated if caught early. Medical misdiagnoses are common, especially when the symptoms are misleading. Being aware is key. Dr Srikanth detailed, “I’ve seen a man misdiagnosed with dementia whose scan revealed a "starry-sky" brain full of cysts, and a woman with seizures and muscle swelling later found to have worm cysts in both brain and muscle tissues.” A big thing that people should understand is that changes in behavior could very easily be a possible signs of brain stress, as well as a neurological problem. Infections, tumors, or certain immune system conditions can all start with small changes in how we act or remember things. Mr. Satani concludes the conversation by explaining how dealing with real-life cases of parasites and how a simple brain infection can cause psychological issues “That experience has stayed with me, because it shows how easily the line between mental health and brain health can be blurred—and how crucial it is to look deeper when something feels off.”