Última actualización:
June 09, 2021
Años publicados: 1986, 1996, 2003, 2009, 2021
NORD gratefully acknowledges Jenna Donaldson, MDCM Candidate, McGill University School of Medicine, and A. Clinton White MD, FACP FIDSA FASTMH, Infectious Disease Division, Department of Internal Medicine, University of Texas Medical Branch, for assistance in the preparation of this report.
Summary
Cysticercosis is caused by the pork tapeworm Taenia solium. Cysticercosis is most seen in endemic regions (Central and South America, sub-Saharan Africa, and Asia (including China, southeast Asia, and India)), where 10 to 20 percent of individuals have evidence of the disease. Cysticercosis can also be found in non-endemic regions in immigrant populations, or in people who have traveled to endemic regions. Cysticercosis can affect anyone at any age. The symptoms of cysticercosis depend on where the infection is in the body, the cyst burden, and the host’s immune response to the infection. Cysts in the nervous system can cause symptoms such as seizures, headache, dizziness, nausea, vomiting, altered mental status, altered vision, accumulation of excessive fluid (cerebrospinal fluid) in the skull (hydrocephalus), and inflammation of the tissue surrounding the brain (arachnoiditis). Cysts in the eye can cause visual disturbances or vision loss, limited eye movement, inflammation in the eye (uveitis), or inflammation of the retina (retinitis). Cysts that develop outside of the nervous system usually do not cause symptoms (asymptomatic), though small hard lumps (nodules) may develop under the skin but will eventually disappear. Treatment of cysticercosis depends on the location of the infection in the body, and is individualized for each person. Cysticercosis located outside of the nervous system usually does not require specific treatment. The treatment for cysticercosis located within the nervous system (neurocysticercosis) consists of antiparasitic therapy, corticosteroids, antiepileptic drugs, and/or surgery.
Introduction
The pork tapeworm (Taenia solium) is a parasite that can cause two types of infections in humans: taeniasis, and cysticercosis. Taeniasis is an intestinal infection with the adult form of the pork tapeworm, resulting from the ingestion of undercooked pork. Conversely, cysticercosis arises from the ingestion of the pork tapeworm’s eggs through fecal-oral contamination, and involves the development of cysts throughout the body, but not in the intestinal tract. This report focuses on cysticercosis, and not taeniasis.
The names of the clinical syndromes of cysticercosis depend on where the cyst(s) are in the body. The development of cysts can happen in many tissues throughout the body. Thus, the nomenclature for cysticercosis can be confusing. The following is a brief review of the terminology used:
If the cysts are located outside the nervous system, then it is called extraneural cysticercosis. Extraneural cysticercosis occurs most commonly in subcutaneous tissue, muscle tissue or heart (cardiac) tissue. If the cysts are in the nervous system, then it is called neurocysticercosis (NCC). In NCC, a cyst can either be located within specific brain tissues (parenchymal neurocysticercosis) or it can be located outside of these specific tissues (extraparenchymal neurocysticercosis). Extraparenchymal forms include cyst development in the fluid filled regions of the brain (intraventricular cysticercosis), in the space surrounding the brain (subarachnoid cysticercosis), in or around the spinal cord (spinal cysticercosis), and in the eye (ophthalmic cysticercosis). Some forms of subarachnoid cysticercosis are termed racemose cysticercosis and are very rare.
Cysticercosis can affect anyone at any age, but the clinical onset in most patients is between the ages of 10 and 40 years old. Symptoms can appear weeks to years after becoming infected with the eggs of the pork tapeworm (T. solium). Most symptoms appear when the cysts start dying. If the cysts are viable, they can “disguise” themselves from the host’s immune system causing only mild symptoms. Few symptoms can arise directly from the presence of the cyst itself. When cysts die, however, it activates the immune system to react against it, and there is a large inflammatory reaction. This inflammation may cause seizures and headache. Cysts can also block the flow of fluid generated in the brain, resulting in increased pressure, puts pressure on the brain and causes symptoms like headache, nausea, dizziness, altered vision etc.
Symptoms usually appear years after becoming infection with the eggs of the pork tapeworm (T. solium). Symptoms may last for many years if medical treatment is not received.
The symptoms of cysticercosis depend on where the infection is in the body, the cyst burden, and the host’s immune response to the infection. Thus, symptoms vary from case to case. The symptoms described below are categorized based on the location of the infection in the body.
Most people with cysticercosis have nervous system involvement (neurocysticercosis). The symptoms of neurocysticercosis vary and are nonspecific. The symptoms of neurocysticercosis depend on if the cysts are in specific brain tissues (parenchymal neurocysticercosis) or if the cysts are outside of these tissues (extraparenchymal neurocysticercosis). An individual can either have parenchymal or extraparenchymal neurocysticercosis or both forms at the same time. Parenchymal neurocysticercosis is the most common form of cysticercosis, occurring in greater than 60 percent of people. Most individuals with parenchymal neurocysticercosis do not have symptoms (asymptomatic). The most common symptom in parenchymal neurocysticercosis is seizures, occurring in 50-80 percent of individuals with parenchymal neurocysticercosis. Some people may have one seizure, while others may have multiple. Having multiple seizures is more common in individuals who have multiple cysts instead of just one cyst. Headaches are also common and a range of neurologic symptoms can rarely occur.
Rarely, individuals with a high level of exposure can acquire hundreds of cysts in the brain, which leads to an intense immune response, causing intense swelling of the brain (cysticercal encephalitis), which is associated with seizures, mental confusion, headache, nausea and vomiting, and occasional fever. This is usually seen in children or women under 30 years old. Cysticercal encephalitis can occur spontaneously, or as a result of antiparasitic therapy.
Extraparenchymal neurocysticercosis is more common in adults than in children and carries a higher risk for complication or death compared to parenchymal neurocysticercosis, though it is much rarer. Extraparenchymal neurocysticercosis forms include cyst development in the fluid filled regions of the brain (intraventricular cysticercosis), in the space surrounding the brain (subarachnoid cysticercosis), in or around the spinal cord (spinal cysticercosis), and in the eye (ophthalmic cysticercosis). Though the symptoms depend on which form of extraparenchymal neurocysticercosis an individual has, common symptoms to all forms of extraparenchymal neurocysticercosis include altered mental status, and high pressure in the brain (elevated intracranial pressure) due to an accumulation of excessive fluid (cerebrospinal fluid) in the skull (hydrocephalus), which causes headaches, nausea, and vomiting. In some cases, individuals who develop hydrocephalus often, in turn, develop swelling of the optic disc (papilledema). Papilledema may cause blurred or double vision.
Symptoms of intraventricular and subarachnoid cysticercosis include headache, nausea and vomiting, dizziness, altered mental status, altered vision, and, rarely, a constellation of findings involving the eyes, mainly the inability to move the eyes upwards and downwards (Parinaud syndrome). In some cases, subarachnoid cysticercosis can cause swelling of a tissue that surrounds the brain (arachnoiditis), which can lead to neck stiffness, intolerance to bright light, and headache (these three symptoms together are termed meningeal signs), stroke, and hydrocephalus. In a rare form of subarachnoid cysticercosis called racemose cysticercosis, there is an accumulation of cysts at the base of the brain, which could result in mental deterioration, coma, and life-threatening complications.
Spinal cysticercosis is rare and occurs in about 1 percent of patients with cysticercosis. Symptoms include a shooting, burning, numbness, or sense of weakness in a particular area of the body (radicular pain), or an abnormal sensation of tingling or pricking commonly described as “pins and needles” (paresthesia).
Ophthalmic cysticercosis arises when cysts form in the eyes. It occurs in approximately 1 to 3 percent of cysticercosis cases. Many people with ophthalmic cysticercosis are asymptomatic. Symptoms include visual disturbances or vision loss, inflammation in the eye (uveitis), inflammation of the retina (retinitis), limited eye movement, protrusion of the eyeball (proptosis), recurrent eye pain, double vision (diplopia), and symptoms related to the nerve that transmits visual information from the eyes to the brain (optic nerve), such as vision loss in one eye, and/or flashing lights. Rarely, the part of the eye responsible for image formation (retina) can detach (retinal detachment), which can threaten vision and needs to be treated quickly.
If the cysts are located outside the nervous system, in places such as subcutaneous tissue, muscle tissue or heart (cardiac) tissue, then it is called extraneural cysticercosis. Individuals with extraneural cysticercosis usually do not have symptoms (asymptomatic). Occasionally, individuals with subcutaneous cysticercosis may have small hard lumps (nodules) that are painless in the arms and chest. These nodules will become swollen and painful right before they begin to disappear. In rare cases, a very large number of cysts can cause enlarged limbs. Rarely, if there are many cysts within a muscle, muscle weakness (myopathy) can develop. Heart involvement (cardiac cysticerci) is usually asymptomatic, but occasionally, there can be heartbeat abnormalities (arrythmias and/or conduction abnormalities).
Cysticercosis is an infection in both humans and pigs. Pigs acquire the infection through the ingestion of segments of the pork tapeworm (proglottids), infected human feces, or food contaminated by infected human feces. Following ingestions, the embryos hatch in the small intestine, get into the blood stream, and travel through the pig’s body to the brain, muscle, and/or other tissues. After three to eight weeks, a fluid filled cyst with an invaginated scolex (tissue cysticerci) develops in the tissue where the embryo travelled.
A human will develop an intestinal infection of the adult pork tapeworm (taeniasis) after consuming undercooked pork that contained cysticerci. Thus, for a human to acquire taeniasis, the pork they consumed needs to have had the infection. Once a human ingests the infected pork, the scolex evaginates and attaches to the human small intestine by its suckers. Segments (proglottids) begin to grow from the scolex, and the result is a growing adult tapeworm. Adult tapeworms can live in the small intestine for years and grow to be very big, in some cases up to 7 meters. The proglottids produces eggs which are shed in human stool. These eggs can be ingested by pigs via the fecal-oral route, where the eggs will hatch in the pig, and the cycle continues as described above. Additionally, these eggs can be ingested by humans via the fecal-oral route. Humans can ingest the eggs in a multitude of ways. The most common method is within a household of an asymptomatic adult pork tapeworm carrier. Other methods include, but are not limited to, produce irrigated with water contaminated with human feces containing the eggs, drinking unsafe water contaminated with eggs, lack of handwashing after using the toilet, fertilization of vegetables with human waste. When a human ingests the eggs, the eggs will hatch, and the larvae will enter the bloodstream, and then distribute to one or more sites over a period of three to eight weeks, and then form cysts (cysticerci). Cysticerci may occur simultaneously in more than one site, or as single cyst. Cysticerci can develop in any organ, but develop most commonly in the subcutaneous tissues, brain and eyes. These cysts cause serious complications (sequalae) if they form in the brain. Cysts located in the nervous system results in neurocysticercosis. Cysts located outside of the nervous system, in subcutaneous tissue, muscle tissue or heart (cardiac) tissue, results in extraneural cysticercosis. The reason cysts develop is because it allows the parasite to evade the host’s immune response and survive. Cysts can survive for years, but will eventually die and degenerate, which provokes the host’s immune system, causing swelling/inflammation of the tissues surrounding the cyst. The pressure arising from the swelling causes symptoms of the infection, though symptoms can also arise directly from the presence of the cyst itself. After the cyst has degenerated and died, the site heals and becomes a nonviable calcified granuloma.
It is important to emphasize that cysticercosis is not acquired directly by eating infected undercooked pork. Instead, eating infected undercooked pork causes taeniasis, since infected pork contains the cysts that will develop into adult pork tapeworms in humans. Infected pork does not contain the eggs that cause cysticercosis. Having taeniasis does not automatically mean also having cysticercosis. Some but not all adult pork tapeworm carriers develop cysticercosis. The only way to acquire cysticercosis is by ingestion of the eggs via fecal-oral route.
It should also be noted that someone with cysticercosis cannot spread the disease to other people. It is only someone with taeniasis who can release the eggs via stool, and subsequent fecal-oral ingestion of these eggs that will result in cysticercosis.
Cysticercosis can affect anyone at any age and affects males and females in equal numbers. Cysticercosis is most seen in endemic regions (Central and South America, sub-Saharan Africa, and Asia (including China, southeast Asia, and India)), where 10 to 20 percent of individuals have evidence of the disease. Within these endemic regions, cysticercosis is most common in rural areas, where pigs roam freely and eat human feces, and where sanitary conditions are less than optimal. Cysticercosis can also be found in non-endemic regions, especially where there are high numbers of immigrants, or in people who have traveled to endemic regions and to countries where sanitation may be substandard and where the water supply may be unsafe. Individuals with no history of pork consumption or travel to endemic areas can also develop cysticercosis, via household contacts of people with an adult pork tapeworm infection (taeniasis).
Neurocysticercosis is the most common parasitic central nervous system infection worldwide. In endemic areas, approximately 30% of people with seizure disorders have neuroimaging abnormalities consistent with neurocysticercosis.
Cysticercosis cases have risen in the United States due to increased immigration from endemic areas. In the United States from 2003 to 2012, there were more than 18,000 hospitalizations for neurocysticercosis.
Approximately 2,000 cases per year are diagnosed in the United States.
846 patients with cysticercosis were reported in Europe between 1990 and 2011. 324 of these cases were from abroad, 74.4% in migrants and 17.6% in European travelers.
Cysticercosis should be suspected in individuals with seizures and/or symptoms of increased pressure in the brain (increased intracranial pressure). The diagnosis of cysticercosis is made based on the combination of characteristic signs and symptoms obtained via a detailed patient history, neuroimaging findings, and exposure to risk factors, such as living in an endemic region, household exposure to a carrier of the adult pork tapeworm infection (taeniasis), or a history of prolonged travel or residence in an endemic region. Neuroimaging studies should include computed tomography (CT), and magnetic resonance imaging (MRI). A special blood test that looks at the immune system (serologic testing with enzyme-linked immunotransfer blot) is recommended as a confirmatory test in people who are suspected of having neurocysticercosis. Very rarely, if the neuroimaging and serology are unable to make the diagnosis, a piece of the suspected infected brain tissue is taken (biopsy) and examined by a specialist (pathologist) to look for neurocysticercosis.
Clinical Testing and Work-Up
Initial evaluation should include a detailed history and physical examination, and neuroimaging studies (CT and MRI). In individuals with diagnostic neuroimaging findings, symptomatic treatment should be started right away (such as medications for seizures or surgery for elevated pressures. However, specific antiparasitic therapy is never an emergency.
All people with diagnosed cysticercosis should receive an eye examination (ophthalmic examination) before beginning treatment to look for ophthalmic cysticercosis. People that will be treated with a prolonged course of steroids should undergo screening for latent tuberculosis infection as well as screening for the parasitic infection caused by the S. stercoralis roundworm (strongyloidiasis). Patients with cysts located outside of the nervous system (extraneural cysticercosis) should undergo imaging of the brain to look for cysts in the nervous system (neurocysticercosis).
Treatment
The treatment of cysticercosis depends on the location of the infection in the body. Cysticercosis located outside of the nervous system is usually benign does not need to be treated. There are medications available to treat cysticercosis for those who do need treatment. The treatment for cysticercosis located within the nervous system (neurocysticercosis) consists of antiparasitic therapy, corticosteroids, antiepileptic drugs, and/or surgery. Treatment is always individualized for each patient.
Antiparasitic drugs have been reported to destroy many of parasites and improve outcomes in some cases. The antiparasitic drugs used are albendazole alone or a combination of albendazole and praziquantel. Albendazole was approved by the Food and Drug Administration (FDA) for the treatment of cysticercosis in 1996. Initiation of antiparasitic drugs is never urgent and symptom management of seizures and/or increased intracranial pressure is the priority. As such, pregnant women are often able to delay antiparasitic therapy until after pregnancy. An eye examination (ophthalmic examination) must be obtained before beginning antiparasitic treatment to look for cysts in the eye (ophthalmic cysticercosis). If cysts in the eye are found, antiparasitic drugs should not be initiated as it can threaten vision. The treatment for ophthalmic cysticercosis is surgical removal of the eye cyst(s). As well, antiparasitic therapy is not to be used (contraindicated) in individuals with higher than normal pressure in the brain (increased intracranial pressure). Antiparasitic drugs can cause a temporary inflammatory reaction which can increase neurocysticercosis symptoms, mainly headaches, during the first week of treatment. Corticosteroids should always be administered alongside antiparasitic therapy to decrease this side effect.
Corticosteroids are used in patients with cysticercosis to prevent the increase in transient symptoms caused by antiparasitic drugs, and to manage fluid build-up in the brain (cerebral edema) which causes increased intracranial pressure. Dexamethasone or prednisone are often the corticosteroid used, and work by decreasing inflammation.
Antiepileptic drugs (AEDs) are used to treat seizures due to neurocysticercosis. The choice of which antiepileptic drug to use depends on cost, drug interactions, and potential side effects. Phenytoin and carbamazepine are often used. In pregnant women, AEDs dangerous for the unborn baby (teratogens) must be avoided.
A variety of surgical techniques may be used to treat certain individuals with cysticercosis. An accumulation of excessive fluid (cerebrospinal fluid) within the skull (hydrocephalus) may be treated by the insertion of a tube (shunt) to drain excess cerebrospinal fluid (CSF) away from the brain and into another part of the body where the CSF can be absorbed. Surgical excision of cysts may be performed in certain cases. Cysticerci affecting the eyes may also be treated surgically.
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For information about trials being conducted at the NIH Clinical Center in Bethesda, MD, contact the NIH Patient Recruitment Office:
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For information about clinical trials sponsored by private sources, contact:
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For information about clinical trials conducted in Europe, contact:
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Journal Articles
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Huan-Zhang L, Xin-Zhong Z, Men-Bao Q, et al. Zhongguo Xue Xi Chong Bing Fang Zhi Za Zhi. 2018;30(1):99-103. doi:10.16250/j.32.1374.2018023
White AC, Jr, Coyle CM, Rajshekhar V, et al. Diagnosis and treatment of neurocysticercosis: 2017 Clinical Practice Guidelines by the Infectious Diseases Society of America (IDSA) and the American Society of Tropical Medicine and Hygiene (ASTMH). Clinical Infectious Diseases, Volume 66, Issue 8. 2018; 49-75. https://doi.org/10.1093/cid/cix1084
Marcin Sierra M, Arroyo M, Cadena Torres M, et al. Extraparenchymal neurocysticercosis: Demographic, clinicoradiological, and inflammatory features. PLoS Negl Trop Dis. 2017;11(6):e0005646. Published 2017 Jun 9. doi:10.1371/journal.pntd.0005646
Mahale RR, Mehta A, Rangasetty S. Extraparenchymal (Racemose) Neurocysticercosis and its multitude manifestations: A Comprehensive Review. J Clin Neurol. 2015;11(3):203-211. doi:10.3988/jcn.2015.11.3.203
Wiwanitkit S, Wiwanitkit V. Racemose cysticercosis: A summary of 5 reported Thai cases. J Neurosci Rural Pract. 2015;6(3):451. doi:10.4103/0976-3147.158750
Brunetti E, White AC Jr. Cestode infestations: hydatid disease and cysticercosis. Infect Dis Clin North Am. 2012;26(2):421-435. doi:10.1016/j.idc.2012.02.001
Garg RK, Malhotra HS. Solitary cysticercus granuloma. Expert Rev Anti Infect Ther. 2012;10(5):597-612. doi:10.1586/eri.12.35
Kraft R. Cysticercosis: an emerging parasitic disease [published correction appears in Am Fam Physician. 2008 Mar 15;77(6):748]. Am Fam Physician. 2007;76(1):91-96.
Garcia HH, Gonzalez AE, Gilman RH; Cysticerosis Working Group in Peru. Diagnosis, treatment and control of taenia solium cysticercosis. Curr Opin Infect Dis. 2003;16(5):411-419. doi:10.1097/00001432-200310000-00007
INTERNET
White AC, Jr. Cysticercosis: Cysticercosis: Epidemiology, transmission, and prevention. UpToDate, Inc. 2020. Updated June 9, 2020. https://www.uptodate.com/contents/cysticercosis-epidemiology-transmission-and-prevention. Accessed June 9, 2021.
White AC, Jr. Cysticercosis: Treatment. UpToDate, Inc. 2020. Updated June 9, 2020. https://www.uptodate.com/contents/cysticercosis-treatment. Accessed June 9, 2021.
White AC, Jr. Cysticercosis: Clinical manifestations and diagnosis. UpToDate, Inc. 2020. Updated June 2, 2020 .https://www.uptodate.com/contents/cysticercosis-clinical-manifestations-and-diagnosis. Accessed June 9, 2021.
Parasites – Cysticercosis. Centers for Disease Control and Prevention. Updated September 22, 2020. https://www.cdc.gov/parasites/cysticercosis/. Accessed June 9, 2021.
Pork Tapeworm and Cysticercosis. EBSCO DynaMed. Updated November 30, 2018. https://www.dynamed.com/topics/dmp~AN~T115222. Accessed June 9, 2021.
Cysticercosis. Genetic and Rare Diseases Information Center. Updated March 20, 2017. https://rarediseases.info.nih.gov/diseases/8194/cysticercosis. Accessed June 9, 2021.
Sid Kirchheimer Pork Tapeworm. EBSCO Health. Updated 2/4/2021. https://healthlibrary.epnet.com/GetContent.aspx?token=38405ca3-6cab-4817-9cba-dc64dc5c69f1&chunkiid=165127. Accessed June 9, 2021.
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