Cysticercosis is a parasitic infection caused by ingesting the larvae of pork tapeworms, or Taenia solium. These larvae, or eggs, may be passed through food, water, or other surfaces contaminated with infected feces, enter the body, and then hatch. Humans most often encounter the larvae through poor hand and food hygiene as these cysts are shed in the stool of infected humans or pigs. Once inside the body, the larvae form cysts in tissues, especially the muscles and brain tissues. Tissue damage will occur as a result, but is dependent on where the cysts develop within the body (1). The cysts, and the tapeworm after development, can migrate to muscle tissue and cause no symptoms, however, serious tissue damage can result if the cyst migrates to the brain, eyes, heart, or spine (2). Blindness, abnormal heart rhythms, and general muscle weakness in the lower extremities as a result of spinal nerve damage can all be a result of the location of infection. Cysticercosis presenting in the brain can cause severe neurological reactions such as seizures and meningisus, as well as headaches, nausea, and confusion. This specific cyst location has it's own term, neurocysticercosis, and is a subset within the broad cysticercosis infection (3).
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| Varied presentations of neurocysticercosis in the brain. Panel A shows two cysts in the cortex of the right cerebral hemisphere. Panel B shows one degenerating cyst in the parietal lobe of the right cerebral hemisphere. Panel C is a cyst in the right lateral ventricle. Panel D showing post-cyst calcifications. Source 3. |
Neurocysticercosis is the infection of T. solium cysts in brain tissue. This infection is acquired through ingestion of tapeworm ova. These develop into larvae, leave the intestines, and migrate through the body by way of the circulatory system. Over 60% of cysticercosis cases develop in the nervous system (3). This location of infection can be very serious, resulting in seizures and in some cases death, and is the leading cause of adult epilepsy worldwide (1).
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| Presentation of cyst infection in the brain, neurocysticercosis. Source 4 |
Cysticercosis, including neurocysticercosis, is most commonly seen in underdeveloped areas of Latin America, Asia, and Africa which have poor sanitation, but can occur world wide. Free-ranging pigs with access to human feces have also been associated with higher instances of the cysticercosis infection. Historically, this condition has been uncommon in the United States, but is becoming increasingly common in the Southwest, and other areas that have experienced a large population migration from endemic areas (1).
Cause
Cysticercosis, including neurocysticercosis cannot be spread through eating undercooked meat. This condition is only contracted through ingestion of food or water containing tapeworm eggs, or through placing hands contaminated with tapeworm eggs in the mouth. If an individual has a tapeworm infection he may infect himself or others with cysticercosis through poor hand hygiene and contamination of other's food or drinks. Autoinfection, or self infection, may occur if an individual with a tapeworm infection, taeniasis, does not wash his hands properly after contact with his contaminated feces and spreads the larvae onto his own food or drink. Individuals living in the same house as a person with an intestinal tapeworm infection have a much higher risk of contracting cysticercosis than other people (1).
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| The most common life cycle of the pork tapeworm and cyst is depicted in this image. Neurocysticercosis infection is shown here. Infection occurs as a result of inadequate food and hand hygiene. Source 5. |
Every year, over 50 million persons are infected worldwide with cysticercosis or neurocysticercosis (5). The CDC considers this infection to be a Neglected Parasitic Infection (NPI), and has thus been targeted by the CDC as one of five parasitic diseases for increased public health action. Neurocysticercosis is the leading cause of adult epilepsy in developing nations (1).
Epidemiology
Human cysticercosis and neurocysticercosis can be found worldwide, and is especially prevalent in areas where humans live in close contact with pigs. Often in this area, pig cysticercosis is also common. This infection is most commonly found in areas of poor sanitation, and frequently in less developed nations. Infection with the Taenia solium larvae can occur in any individual in any country regardless of development level. The only necessary requirement for infection is ingestion of the tapeworm larvae.
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