Cysticercosis is a rare infectious disease caused by the presence and accumulation of the larval cysts of a tapeworm (cestode) within tissues of the body. The scientific name for the tapeworm that causes cysticercosis is Taenia solium (T. solium), which is also known as the pork tapeworm. T. solium cysts (cysticerci) may affect any area of the body including the brain, a condition known as neurocysticercosis. Symptoms vary from case to case. If cysticerci are located in the brain, central nervous system abnormalities may occur, most often seizures and headaches. Cysticercosis may also affect the eyes, spinal cord, skin and heart.
The symptoms of cysticercosis vary from case to case depending upon the number and location of cysticerci within the body. Cysticerci are often found in muscle tissue. In some cases, the cysts have been located in brain, eyes or heart tissue. Some individuals with cysticercosis will exhibit no symptoms (asymptomatic) or very mild symptoms.
Many individuals with cysticercosis have central nervous system involvement (neurocysticercosis). However, many individuals with neurocysticercosis do not exhibit or develop symptoms. The specific symptoms of neurocysticercosis depend upon the number and location of cysts involved as well as an individual’s immune system response.
The four basic types of neurocysticercosis are parenchymal, subarachnoid, intraventricular and spinal. Symptoms common to all forms of neurocysticercosis include headaches, seizures and accumulation of excessive cerebrospinal fluid (CSF) in the skull (hydrocephalus) causing increased pressure on the tissues of the brain, resulting in a variety of symptoms including headaches, nausea, dizziness, changes in vision, 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.
Parenchymal disease may be associated with headaches, seizures, intellectual impairment, behavioral changes, and hydrocephalus. Impairment of the ability to coordinate voluntary movements (ataxia) and muscular weakness on one side of the body (hemiparesis) may also occur with this form of neurocysticercosis.
Subarachnoid cysticercosis is associated with chronic inflammation of the membranes covering the brain (meninges), headaches, seizures, and hydrocephalus. Intraventricular cysticercosis may cause obstructive hydrocephalus. A variant of this form of cysticercosis known as racemose cysticercosis may occur. Racemose cysticercosis is characterized by accumulation of cysts at the base of the brain potentially resulting in mental deterioration, coma and life-threatening complications. Cysts affecting the spinal cord are rare, but may result in meningitis or compression of the spinal cord.
In some cases, individuals may experience heavy central nervous system infections, which can potentially result in life-threatening complications such as stroke or coma (cysticercal encephalitis). Individuals with heavy CNS infections often first develop muscle pain (myalgia), weakness, and fever.
Ocular cysticercosis occurs when cysts form in the eyes. Associated symptoms may include eye pain, loss of vision and separation of the nerve-rich membrane lining the eyes (retina) from its underlying, supporting tissue (retinal detachment). In some cases cysticercosis may only affect the eyes (isolated ocular cysticercosis).
In some cases, cysts may form under the skin causing small lumps. These lumps usually do not cause any additional symptoms.
Cysticercosis results from the ingestion of the eggs of the tapeworm known as Taenia solium. Ingestion of contaminated pork usually results in adult tapeworm infection not cysticercosis.
The normal life cycle of pork tapeworms is as follows: the pig ingests tapeworm eggs. In the pig’s intestine, the eggs hatch and burrow through the gut wall into muscle tissue. There they encyst and develop into larval cysts called cysticerci. When the pig is killed and its meat eaten by a person, the cysticerci are released and attach themselves to the wall of the intestine where they develop into egg producing adult tapeworms. This is known as adult tapeworm infection and usually causes no symptoms. However, individuals with adult tapeworm infection can develop cysticercosis because they will release T. solium eggs through their feces and can potentially ingest the eggs (autoinfection). These individuals may also regurgitate or reflux T. solium eggs from the intestines into the stomach.
Cysticercosis usually results when an individual ingests food, especially pork, contaminated with T. solim eggs (rather than the larvae). The eggs travel via the bloodstream eventually finding their way into the muscle, subcutaneous, brain, and other tissues of the body. After 60 to 90 days the eggs encyst and develop into larval cysts (cysticerci). The cysts remain in the body tissue indefinitely, unable to proceed to the next stage of their life cycle. As long as these larvae remain alive, they appear to be able to “disguise” themselves from the host’s immune system causing only mild symptoms. However, eventually the larvae die off causing a strong immune defensive reaction against it or the cyst surrounding it. The cyst itself may become enormous. Such inflammatory reactions can cause severe illness, particularly if the cysticerci are lodged in the central nervous system or heart.
Cysticercosis affects males and females in equal numbers. Some forms of cysticercosis such as racemose cysticercosis occur more frequently in females. Approximately 1,000 cases of cysticercosis are reported each year in the United States. The disease is more common in Mexico, Latin America, South America, Eastern Europe, and Southeast Asia. Cysticercosis cases have risen in the United States following increased immigration from endemic areas.
A diagnosis of cysticercosis may be made based upon a thorough clinical evaluation, a detailed patient history and a variety of specialized tests. Magnetic resonance imaging (MRI) and computed tomography (CT) scan may be used to diagnose neurocysticercosis.
In many cases individuals with cysticercosis do not require treatment.
In cases where symptoms are present, individuals are often treated with drugs or surgery. The antiparasitic drug albendazole (Albenza) was approved by the Food and Drug Administration (FDA) for the treatment of cysticercosis in 1996. For more information on this drug, contact:
Smithkline Beecham Pharmaceuticals
Division of Smith Kline Beecham Corporation
One Franklin Plaza
PO Box 7929
Philadelphia, PA 19101
Before the development of albendazole, the antiparasitic drug praziquantel (Biltricide) was often used to treat individuals with cysticercosis. Infection with an adult tapeworm can be eliminated using antiparasitic medications such as niclosamide or paronomycin. As described above, care must be taken to avoid the release of large quantities of eggs from the dying tapeworms as this may cause cysticercosis. Seizures sometimes associated with neurocysticercosis may be treated with anti-seziure medications (anticonvulsants) such as phenytoin (Dilantin) or lorazepam (Antivan).
A variety of surgical techniques may be used to treat certain individuals with cysticercosis. 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 (cysticerci) may be performed in certain cases. Cysticerci affecting the eyes may also be treated surgically.
Other treatment is symptomatic and supportive.
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Bennett JC, Plum F., eds. Cecil Textbook of Medicine. 20th ed. Philadelphia, PA: W.B. Saunders Co; 1996:1925-6.
Fauci AS, et al., eds. Harrison’s Principles of Internal Medicine, 14th Ed. New York, NY: McGraw-Hill, Inc; 1998:1224-5.
Adams, RD, et al., eds. Principles of Neurology. 6th ed. New York, NY: McGraw-Hill, Companies; 1997:738.
Mandell GL, et al., eds. Mandell, Douglas and Bennett’s Principles and Practice of Infectious Diseases. 4th ed. New York, NY: Churchill Livingstone Inc; 1995:2544-52.
Garcia HH, et al., Diagnosis, treatment and control of Taenia solium cysticercosis. Curr Opin Infect Dis. 2003;16:411-9.
Ito A, et al., Recent advances in basic and applied science for the control of taeniasis/cysticercosis in Asia. Southeast Asian J Trop Med. 2003;33:79-82.
Garcia HH, et al., Taenia solium cysticercosis. Lancet. 2003;362:547-56.
Waltrath Jd, et al., Cysticercosis isolated to the orbit. Ophthal Plast Reconstr Surg. 2003;19:243-4.
Kalra V, et al., Efficacy of albendazole and short-course dexamethasone treatment in children with 1 or 2 ring-enhancing lesions of neurocysticercosis: a randomized controlled trial. J Pediatr. 2003;143:111-4.
Chowdhary A, et al., Ocular cysticercosis – a profile. Trop Doct. 2003;33:185-8.
Horton J, Albendazole: a broad spectrum anthelminthic for treatment of individuals and populations. Curr Opin Infect Dis. 2002;15:599-608.
Narula G, Bawa KS, Neurocysticerocis – new millennium, ancient disease and unending debate. Indian J Pediatr. 2003;70:337-42.
Engels D, et al., The control of human (neuro)cysticercosis: which way forward? Acta Trop. 2003;87:177-82.
Schantz PM, Tsang VC The US Centers for Disease Control and Prevention (CDC) and research and control of cysticercosis. Acta Trop. 2003;87:161-3.
Sarti E, Rajshekhar V, Measures for protection and control of Taenia solium taeniosis and cysticercosis. Acta Trop. 2003;87:137-43.
Lightowlers MW, Vaccines for prevention of cysticercosis. Acta. Trop. 2003;87:129-35.
Tenzer R. Cysticercosis. eMedicine Journal. 2002;1:11pp.
Giordano TP. Cysticercosis. eMedicine Journal. 2001;1:10pp.
FROM THE INTERNET
Centers for Disease Control and Prevention. Division of Parasitic Diseases. Parasitic Disease Information. Fact Sheet: Cysticercosis. Available at: http://www.cdc.gov/ncidod/dpd/parasites/cysticercosis/factsht_cysticercosis.htm