Taenia solium - Cysticercosis and Taeniasis

Cysticercosis is transmitted when humans consume food or water contaminated with Taenia solium eggs or ingest fomites containing T. solium eggs, which are excreted in human feces.  Once ingested, the eggs hatch into larvae in the host's intestines then migrate and develop into cysticerci (larval cysts) in the central nervous system (CNS), muscles, skin, and/or eyes.  Taeniasis occurs when humans consume raw or undercooked pork infected with cysticerci. The cysticerci mature into adult tapeworms that reside in the small intestine for up to several years.  Adult tapeworms produce eggs, which are passed through human feces into the environment.  Autoinfection can occur when an individual with taeniasis infects themself with tapeworm eggs, leading to the development of cysticercosis. T. solium is found worldwide wherever pigs are raised, but individuals in areas with inadequate sanitation and human fecal contamination of swine feeding zones are at increased risk for infection. 

Cysticercosis symptoms may present several years after infection and vary based on cyst location, cyst number, and host response.  In most locations, cysticerci cause little to no symptoms and may degenerate without treatment.  Neurocysticercosis is the most serious manifestation and occurs when cysts form in the central nervous system (CNS). Testing should be considered in all individuals presenting with new-onset seizures or signs of increased intracranial pressure who may have been exposed to tapeworm carriers. 

Neurocysticercosis, the most clinically significant manifestation of Taenia solium infection, is a leading cause of preventable epilepsy worldwide and hydrocephalus in endemic areas.  Manifestations vary but the most common are seizures and/or increased intracranial pressure.  Affected individuals often initially present with headaches or migraines.  Less common symptoms include visual impairment, mass lesions, spinal radiculopathies, and strokes.  Specific guidelines have been developed for the diagnosis and management of neurocysticercosis by the World Health Organization (WHO), the Infectious Diseases Society of America (IDSA), and the American Society of Tropical Medicine and Hygiene (ASTMH). ^, 

The use of both central nervous system (CNS) imaging and serologic testing is recommended because one test may be negative and the other positive in affected individuals, depending on the location and number of cysts. For instance, a patient with a single cyst or a few cysts might have negative serologic results but visible lesions on imaging. Conversely, a patient with cysts outside the brain may have negative CNS imaging results but positive serologic tests.