Cysticercosis
Medical Author: Steven E. Doerr, MD
Medical Editor: Charles Davis, MD, PhD
What is cysticercosis?
Cysticercosis is a systemic parasitic infestation caused by the pork
tapeworm, Taenia solium. The symptoms of this illness are caused by the
development of characteristic cysts (cysticerci) which most often affect the
central nervous system (neurocysticercosis), skeletal muscle, eyes, and skin.
Many individuals with cysticercosis never experience any symptoms
(asymptomatic).
The tapeworm responsible for causing cysticercosis is endemic to many parts
of the developing world, including Latin America, Asia, and sub-Saharan Africa.
The incidence of cysticercosis has increased in the United States due to
increased immigration from developing countries, and it is estimated that about
1,000 new cases of cysticercosis are diagnosed annually in the United States.
Neurocysticercosis is a leading cause of adult-onset seizures worldwide.
Historically, the disease has been recognized since about 2000 B.C. by the
Egyptians and later described in pigs by Aristotle. The disease was also
recognized by Muslim physicians and is thought to be the reason for Islamic
dietary prohibition of eating pork. In the 1850s, German investigators
described the life cycle of T. solium.
What causes cysticercosis?
Cysticercosis is caused by the dissemination of the larval form of the pork
tapeworm, Taenia solium. When the eggs of Taenia solium are ingested by humans,
the tapeworm eggs hatch and the embryos penetrate the intestinal wall and reach
the bloodstream. The formation of cysts in different body tissues leads to the
development of symptoms, which will vary depending on the location and number of
cysts.
How is cysticercosis transmitted?
Humans are the host for Taenia solium, and they may carry the tapeworm in
their intestine, often without symptoms. The tapeworm eggs are periodically shed
in the feces by the human reservoir, and typically pigs ingest the eggs in
contaminated food or water. The pigs subsequently become infected and develop
cysticerci in their body tissue. When humans eat infected raw or undercooked
pork, the life cycle of the tapeworm is complete and the cycle continues.
Human cysticercosis, however, develops after humans ingest Taenia solium
eggs. The eggs are typically spread via food, water, or surfaces contaminated
with infected feces. Oftentimes, the eggs may be spread from the hands of
infected food handlers who do not clean their hands or from foods
fertilized/irrigated with water containing infected human feces. Though the
source of this fecal-oral transmission often occurs from other infected
individuals, it is also possible for individuals who carry the tapeworm to autoinfect themselves. The life cycle of
T. solium is shown below, and pictures of the cysts in
tissues can be found in the last reference listed below.
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| Life cycle of T. solium with resulting cysticercosis. Photo courtesy of the CDC |
Next: What are the symptoms of cysticercosis? »
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