Taenia solium, is known as the pork tapeworm. It infects pigs and humans in Asia, Africa, the Philippines,
South America, parts of Southern Europe, and pockets of North America. Infection in humans with Taenia
solium larvae (cysticerci) is called cysticercosis.
Cysticercosis is rare in most industrialized nations but is endemic in developing areas such as Latin
America, Asia and Africa. Most of the cases of cysticercosis in the United States are associated with
immigrants from these countries.
Tapeworm infection is acquired by eating raw or undercooked meat of infected animals or ingesting
contaminated food and water. Beef generally carries Taenia saginata while pork carries Taenia solium.
Certain freshwater fish and salmon may also carry a tapeworm called Diphyllobothrium latum.
The T. solium larvae develop in the human intestine into the adult tapeworm over 2 months and can attain
lengths greater than 12 feet. In the intestine, T. solium can survive for years. The adult tapeworms attach
to the small intestine by their scolex and reside in the small intestine. Mixed infections of both Taenia
saginata and Taenia solium parasites can occur. Humans are the definitive host for T. solium, which
means that the adult tapeworms are found only in the intestine of humans.
Tapeworms are segmented, and each segment or proglottid of the female is capable of producing eggs.
The groups of proglottids from the beef tapeworm are capable of movement and actively crawl out through
the anus. Cattle and pigs can be infected by ingesting vegetation contaminated with eggs or pregnant
proglottids. In the animal's intestine, they hatch, invade the intestinal wall, and migrate to the muscles,
where they develop into cysticerci. A cysticercus can survive for several years in the animal. Humans
become infected by ingesting raw or undercooked infected meat.
Taenia solium is found worldwide. Because pigs are intermediate hosts of the parasite, completion of their
life cycle occurs in regions where humans live in close contact with pigs and eat undercooked pork.
Taeniasis and cysticercosis are very rare in predominantly Muslim countries, as Islam forbids the
consumption of pork. Infected humans can also cause others to become infected if careful hygiene
practices are not done.
Many sites of infection have been documented but the central nervous system has been the most
common. Presence of the cysticerci in the brain may cause increased cranial pressure, seizures and
altered mental states, epilepsy and even death. When death occurs, it is most often due to involvement of
the brain resulting in hydrocephalus, cerebral edema, cerebral compression, or epileptic seizures.
Cysticercosis, or neurocysticercosis, is the most common parasitic infestation of the central nervous
With neurocysticercosis seizures, and headaches are the most common symptoms. However, confusion,
lack of attention to people and surroundings, difficulty with balance, hydrocephalus (compression of the
brain tissue due to obstruction of cerebrospinal fluid flow) may also occur. Often, there are few symptoms
until the parasite dies. When the parasite dies, the host's immune system detects the worm's remains and
attacks them, causing swelling and scarring. This is what causes most of the symptoms. Spinal cord
lesions can lead to partial loss of motor control, weakness, and even paralysis.
In muscles, cysts cause painless swelling or create nodules under the skin. If cysts form in the eye, they
can impair vision by floating in the eye and can cause blindness by causing swelling and detachment of the
retina. Heart lesions can lead to abnormal rhythms or heart failure (rare). The most dangerous symptoms
are a result of encystment in the central nervous system.
It is possible to avoid infection with T. solium by not eating undercooked pork and food and water
contaminated with human feces. Extra care should be taken in places with poor hygiene or meat inspection
laws. Freezing infested pork for a prolonged period will also kill cysticerci. The following list describes
important actions to prevent infection with tapeworm:
*Adequate sewage treatment and disposal
*Good hygiene and hand washing after using the toilet will prevent self-infection in a person already
infected with tapeworms.
*Improvement of living conditions, especially safe treatment of sewage used for farming
Neurocysticercosis is difficult to diagnose in its early stage and may be apparent only when the first
neurological symptoms start, or when a CT scan, or an MRI of the brain is performed for other reasons.
Antibody tests or a biopsy of the affected area may be necessary to complete the diagnosis.
It is still controversial whether patients benefit from treatment, because live cysticerci do not provoke
seizures; only dead or dying parasites invoke an inflammatory response and seizures. In theory, therefore,
treating a patient with drugs that kill living parasites can induce seizures in someone who is otherwise well
and seizure-free; likewise, treating someone with seizures may not have any effect on outcome as the
parasites are already dead and no improvement can be expected.
Reliable diagnosis of cysticercosis requires multiple testing methods such as radiography and the
qualitative screening of serum IgG antibodies to Taenia solium using an Enzyme Linked Immunoabsorbant
Assay (ELISA) technique.
Although use of cyst vesicular antigen has helped to increase its sensitivity and specificity, significant cross
reactions with Echinococcosis occurs. If Echinococcus infection cannot be ruled out in the differential
diagnosis, a positive sample should be confirmed by other means (i.e. immunoblot offered by the CDC) or
by other non-serological means. Repeated examination and concentration techniques will increase the
likelihood of detecting light infections. Nevertheless, speciation of Taenia solium is impossible if solely
based on microscopic examination of eggs, because all Taenia species produce eggs that are
morphologically identical. Eggs of Taenia species are also indistinguishable from those produced by
cestodes of the genus Echinococcus.