Neurocystercercosis is a parasitic disease that is endemic (naturally occurring in a region) in many countries throughout Central and South America. It is caused by the pork tapeworm (Taenia solium), and is on the rise in the United States largely as a result of immigration.
People most commonly ingest the pork tapeworm by eating undercooked pork in an area where the parasite is common. Tapeworm eggs are shed in the pigs’ stool, and get into the meat via poor hygiene. If the pork is not cooked to a high enough temperature, the eggs remain viable. It can also be spread by cross contamination to unwashed produce, or via fecal/oral transmission by an infected person.
Once the eggs are in your stomach, gastric acid breaks down the outside of the egg, and the larva can enter your bloodstream. They can then make cysts in the tissues of your body (called cystercercosis), including your eyes or brain. When the cysts are in your brain, it is called neurocystercercosis.
This parasite was basically unheard of in the U.S. 20 years ago, but incidence has been increasing due to the larger population of immigrants from countries where the tapeworm is more common. Tourists visiting areas where it is native can also pick up the parasite. Neurocystercercosis is not something you run into every day in the U.S., but cases are increasing enough to raise concerns about whether it should be a reportable illness for public health tracking purposes.
In some areas such as Los Angeles, greater than 10 percent of first time seizure cases presenting at emergency departments are related to neurocystercercosis. It is extremely uncommon in some states, while increasing in others. Many people have no symptoms, and the parasite most commonly stays in muscles, but when the cysts are located in the brain or eye, they can cause serious problems.
This parasite can be treated if caught early, but prevention is ideal. When traveling to countries where the pork tapeworm is common, only eat pork that is cooked well done. Always wash fruits and vegetables well, and wash your hands thoroughly before and after toileting and eating.