eMedicine Specialties > Pediatrics: General Medicine > Parasitology
Taenia Infection
Updated: Jan 23, 2009
Introduction
Background
Of the 32 recognized species of Taenia, only Taenia solium and Taenia saginata are medically important. However, recent epidemiologic studies in Southeast Asia have identified a third Taenia species in humans, known as the Asian species.1,2 Cysticercosis is the development of extraintestinal encysted larval forms of T solium in various organs (see Cysticercosis). The CNS is involved in 60-90% of cases; this condition is termed neurocysticercosis (NCC). For more information, see Neurocysticercosis.
Cysticercosis caused by T saginata (also called the cattle or beef tapeworm) is rare; T saginata has far lower impact on human health than T solium. Differentiating between T solium and T saginata infections is important because both infections are endemic in Southeast Asia, Africa, Europe, and Central and South America. Infection in children usually goes unrecognized.
Pathophysiology
Adult tapeworms live in the human small intestine. Humans pass gravid eggs in feces; these mature eggs contaminate pastures and barnyards, where cattle and pigs ingest them. Upon reaching the alimentary canal of infected animals, the embryos are released, penetrate the gut wall, and enter the circulation. The embryos filter from the circulation and encyst in muscular tissue. Larvae (ie, cysticerci) become infectious within 2-3 months. Humans develop a tapeworm infection by eating raw or undercooked beef or pork. The cysticercus becomes activated, attaches to the wall of the small intestine by the scolex, and becomes a mature tapeworm. This maturation process takes 10-12 weeks for T saginata and 5-12 weeks for T solium. A single tapeworm produces an average of 50,000 eggs per day and may live 25 years.
Humans can also act as an intermediate host for T solium. Cysticercosis results from human ingestion of T solium eggs through fecal contamination, reverse peristalsis of gravid proglottids, or autoinfection. The cysticerci may develop in any organ, and their effects depend entirely on the location of the cysticerci.
A coenurus is the larval stage of Taenia multiceps, Taenia serialis, and Taenia brauni. Adult tapeworms develop in dogs or other canids that ingest coenurus larvae in the tissues of various intermediate hosts. These hosts include sheep, goats, hares, rabbits, and other herbivores for T multiceps; hares, rabbits, and other rodents for T serialis; and gerbils for T brauni. Each protoscolex within a coenurus can mature into an adult tapeworm after ingestion by a canid host. Adult worms produce eggs, which are passed in feces; these eggs are morphologically similar to taeniid eggs. Ingestion of eggs by an appropriate intermediate host or by humans leads to development of coenurus. Coenuri are cysts that contain many protoscolices attached in rows on the internal membrane of the cyst.
Frequency
United States
Cysticercosis is primarily an imported disease. Approximately 1000 cases are diagnosed each year. Most occur in persons who have immigrated, primarily from Latin America. Cysticercosis has also developed following close contact with recently immigrated, infected individuals. Although some patients with NCC are born in the United States, many have traveled to rural areas in countries where the condition is endemic. Locally acquired infections have been confirmed in Los Angeles, New York, Chicago, and elsewhere. Although T saginata infection occurs worldwide, prevalence in the United States is less than 1% because most US cattle are free of the parasite.
International
Approximately 50 million people worldwide are infected by T saginata or T solium. Approximately 50,000 people die annually of cysticercosis. T saginata is common in cattle-breeding regions. Areas with the highest (ie, >10%) prevalence are central Asia, the Near East, and central and eastern Africa.3 Areas with low (ie, 1%) prevalence are Southeast Asia, Europe, and Central and South America.
- T solium is endemic in Central and South America, Southeast Asia, India, the Philippines, Africa, Eastern Europe, and China. Areas of highest prevalence include Latin America and Africa. In some regions of Mexico, prevalence may reach 3.6% of the general population.
- T multiceps has been reported in the Americas and parts of Europe and Africa.
- T serialis infections occur in the United States and Canada.
- T brauni has been reported in Africa.
Mortality/Morbidity
Most intestinal taeniid infections are asymptomatic. When symptoms occur, they are usually mild and involve abdominal pain, anorexia, weight loss, or malaise. Cysticercosis causes a mass effect in various vital organs (eg, brain, eye, heart). The mortality rate for cysticercosis is low and is generally caused by complications such as encephalitis, increased intracranial pressure secondary to edema and/or hydrocephalus, and stroke.
Race
All races are equally affected.
Sex
Both sexes are equally affected.
Age
All ages are susceptible to infection. The age at which raw meat consumption begins is the primary determinant. T solium taeniasis has been reported in children older than 2 years in certain rural communities of Mexico.
Clinical
History
- Taeniasis
- Most individuals with taeniasis are either asymptomatic or have mild-to-moderate complaints.
- The most common complaint is passage (active or passive) of proglottids, which is associated with slight discomfort. Other symptoms include the following:
- Colicky abdominal pain (more common in children)
- Nausea
- Weakness
- Loss of appetite
- Increased appetite
- Headache
- Constipation
- Dizziness
- Diarrhea
- Pruritus ani
- Hyperexcitability
- Abdominal pain and nausea are reportedly more common in the morning and are characteristically relieved by eating small amounts of food. Children are more symptomatic than adults and often manifest change of appetite, both increased and decreased. Symptoms in infants are more pronounced and consist of vomiting, diarrhea, fever, weight loss, and irritability.
- The most common serious complication of adult tapeworm infection is appendicitis. Other reported complications include obstruction of bile ducts, pancreatic duct and tapeworm growth in ectopic locations (eg, middle ear, adenoid tissue, uterine cavity). A mild eosinophilia of 5-15% may occur in 5-45% of patients; higher levels are rare.
- Cysticercosis and neurocysticercosis (NCC)
- In cysticercosis, the cysticerci are most often located in subcutaneous and intermuscular tissues, followed by the eye and then the brain. The CNS is involved in 60-90% of patients (ie, NCC). Most patients have more than one cyst; as many as 200 cysts have been reported.
- NCC symptoms include 3 characteristic syndromes: convulsions and/or seizures, intracranial hypertension, and psychiatric disturbances, which may occur separately or simultaneously.4 Onset can be insidious (eg, elevated intracranial pressure) or abrupt (eg, floating cysticerci suddenly block cerebrospinal fluid [CSF]).
- Convulsions and/or seizures: Seizures are caused by the localization of cysticerci in brain parenchyma. Children most often present with seizures, which are focal with acute onset. Cysticercosis is the most common cause of epilepsy in endemic areas5 and is the sole manifestation in as many as one third of patients.
- Intracranial hypertension: This is caused by obstruction of CSF by intraventricular brain cysts. Symptoms include headache, nausea, vomiting, vertigo, and papilledema.
- Psychiatric disturbances: Although changes in personality and mental status occur more often in adults than in children, behavioral changes and learning disabilities were reported in a study of 25 affected children.6
- Other possible infections
- Ocular cysticercosis: The subretinal space, vitreous, and conjunctiva are the most frequent sites of infection. Common manifestations of infection include severe pain and blurred or lost vision.
- Muscular and dermatologic cysticercosis: Cysticerci in muscles often are associated with NCC. Any muscle mass may be involved and appear as acute myositis. However, most patients are asymptomatic. Subcutaneous nodules may be evident.
- Coenurosis: Clinical manifestations are determined by the site of the coenurus larvae. Patients with cerebral coenurosis can present with seizure or intracranial hypertension. Ocular coenurosis manifests as a red and painful eye.
Physical
Most children with intestinal taeniasis appear healthy. Physical findings may include the following:
- Weight loss, caused by loss of appetite, is more pronounced in infants than in adults.
- Subcutaneous nodules are less common in children than in adults.
- Neurologic abnormalities in some children with NCC may manifest as hemiparesis, sensory disturbances, and papilledema.
- Intraocular larva may be evident.
- Muscular pseudohypertrophy may occur.
Causes
- Taeniasis is caused by ingesting inadequately cooked beef or pork that contains the larvae or cysticerci of T saginata or T solium. Cysticercosis, which is caused by ingesting eggs of T solium, occurs when larvae are deposited in skeletal muscle, brain, eyes, and other organs. Taeniasis is endemic in countries where both T saginata and T solium are common and public hygiene is poor. A species of Taenia recently identified in many Southeast Asian countries resembles T saginata at the molecular level, and its ingestion in inadequately cooked pork causes an intestinal infection. This close relationship with T saginata has led to the assumption that it does not cause human cysticercosis because human cysticercosis is caused almost exclusively by T solium.
- Coenurosis results when humans accidentally ingest mature T multiceps or T serialis eggs, usually in contaminated fruits or vegetables. Approximately 100 cases of coenurosis have been reported, primarily in tropical Africa, with the remainder in North and South America and South Africa. Interestingly, the cases in central Africa rarely involved the CNS, whereas more than 75% of the cases elsewhere had CNS involvement. Larvae of these species may be inoculated directly into a child's conjunctiva and skin as the child plays on contaminated ground.
More on Taenia Infection |
 Overview: Taenia Infection |
| Differential Diagnoses & Workup: Taenia Infection |
| Treatment & Medication: Taenia Infection |
| Follow-up: Taenia Infection |
| Multimedia: Taenia Infection |
| References |
| Further Reading |
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References
Ito A, Wandra T, Sato MO, et al. Towards the international collaboration for detection, surveillance and control of taeniasis/ cysticercosis and echinococcosis in Asia and the Pacific. Southeast Asian J Trop Med Public Health. 2006;37 Suppl 3:82-90. [Medline].
Craig P, Ito A. Intestinal cestodes. Curr Opin Infect Dis. Oct 2007;20(5):524-32. [Medline].
Del Brutto OH. Neurocysticercosis. Semin Neurol. Sep 2005;25(3):243-51. [Medline].
Carpio A. Neurocysticercosis: an update. Lancet Infect Dis. Dec 2002;2(12):751-62. [Medline].
Garcia HH, Del Brutto OH. Neurocysticercosis: updated concepts about an old disease. Lancet Neurol. Oct 2005;4(10):653-61. [Medline].
Morales NM, Agapejev S, Morales RR, Padula NA, Lima MM. Clinical aspects of neurocysticercosis in children. Pediatr Neurol. Apr 2000;22(4):287-91. [Medline].
Mazumdar M, Pandharipande P, Poduri A. Does albendazole affect seizure remission and computed tomography response in children with neurocysticercosis? A Systematic review and meta-analysis. J Child Neurol. Feb 2007;22(2):135-42. [Medline].
Barton Behravesh C, Mayberry LF, Bristol JR, et al. Population-based survey of taeniasis along the United States-Mexico border. Ann Trop Med Parasitol. Jun 2008;102(4):325-33. [Medline].
Botero D, Tanowitz HB, Weiss LM, Wittner M. Taeniasis and cysticercosis. Infect Dis Clin North Am. Sep 1993;7(3):683-97. [Medline].
Carabin H, Budke CM, Cowan LD, Willingham AL 3rd, Torgerson PR. Methods for assessing the burden of parasitic zoonoses: echinococcosis and cysticercosis. Trends Parasitol. Jul 2005;21(7):327-33. [Medline].
Conlan J, Khounsy S, Inthavong P, Fenwick S, Blacksell S, Thompson RC. A review of taeniasis and cysticercosis in the Lao People's Democratic Republic. Parasitol Int. Sep 2008;57(3):252-5. [Medline].
DeGiorgio CM, Sorvillo F, Escueta SP. Neurocysticercosis in the United States: review of an important emerging infection. Neurology. Apr 26 2005;64(8):1486; author reply 1486. [Medline].
Drimousis PG, Stamou KM, Koutras A, Tsekouras DK, Zografos G. Unusual site of recurrent musculoskeletal hydatid cyst: case report and brief review of the literature. World J Gastroenterol. Sep 14 2006;12(34):5577-8. [Medline].
Fleury A, Hernandez M, Avila M, et al. Detection of HP10 antigen in serum for diagnosis and follow-up of subarachnoidal and intraventricular human neurocysticercosis. J Neurol Neurosurg Psychiatry. Sep 2007;78(9):970-4. [Medline].
Garcia HH, Del Brutto OH. Taenia solium cysticercosis. Infect Dis Clin North Am. Mar 2000;14(1):97-119, ix. [Medline].
Garcia HH, Del Brutto OH, Nash TE, et al. New concepts in the diagnosis and management of neurocysticercosis (Taenia solium). Am J Trop Med Hyg. Jan 2005;72(1):3-9. [Medline]. [Full Text].
Garcia HH, Evans CA, Nash TE, et al. Current consensus guidelines for treatment of neurocysticercosis. Clin Microbiol Rev. Oct 2002;15(4):747-56. [Medline]. [Full Text].
Garcia HH, Gonzalez AE, Evans CA, et al. Taenia solium cysticercosis. Lancet. Aug 16 2003;362(9383):547-56. [Medline].
Garcia HH, Gonzalez AE, Gilman RH, Cysticerosis Working Group in Peru. Diagnosis, treatment and control of Taenia solium cysticercosis. Curr Opin Infect Dis. Oct 2003;16(5):411-9. [Medline].
Garcia HH, Moro PL, Schantz PM. Zoonotic helminth infections of humans: echinococcosis, cysticercosis and fascioliasis. Curr Opin Infect Dis. Oct 2007;20(5):489-494. [Medline].
Garcia LS, Bruckner DA. Intestinal cestodes. In: Diagnostic Medical Parasitology. 3rd ed. 1997:308-24.
Garg RK. Neurocysticercosis: a pictorial review. Infect Dis Clin Pract. July 2008;16(4):210-7.
Gerber JS, Shah SS. Picture of the month. Neurocysticercosis. Arch Pediatr Adolesc Med. Oct 2006;160(10):1081. [Medline].
Hawk MW, Shahlaie K, Kim KD, Theis JH. Neurocysticercosis: a review. Surg Neurol. Feb 2005;63(2):123-32; discussion 132. [Medline].
Homans J, Khoo L, Chen T, et al. Spinal intramedullary cysticercosis in a five-year-old child: case report and review of the literature. Pediatr Infect Dis J. Sep 2001;20(9):904-8. [Medline].
Ito A, Takayanagui OM, Sako Y, et al. Neurocysticercosis: clinical manifestation, neuroimaging, serology and molecular confirmation of histopathologic specimens. Southeast Asian J Trop Med Public Health. 2006;37 Suppl 3:74-81. [Medline].
Kraft R. Cysticercosis: an emerging parasitic disease. Am Fam Physician. Jul 1 2007;76(1):91-6. [Medline].
Leonard R, Adickes ED, Brumback RA. Neurocysticercosis. J Child Neurol. Jul 2006;21(7):589-90. [Medline].
Loos-Frank B. An up-date of Verster's (1969) 'Taxonomic revision of the genus Taenia Linnaeus' (Cestoda) in table format. Syst Parasitol. Mar 2000;45(3):155-83. [Medline].
Lucato LT, Guedes MS, Sato JR, Bacheschi LA, Machado LR, Leite CC. The role of conventional MR imaging sequences in the evaluation of neurocysticercosis: impact on characterization of the scolex and lesion burden. AJNR Am J Neuroradiol. Sep 2007;28(8):1501-4. [Medline].
Mandell GH, Bennett JE, Dolin R. Principles and Practice of Infectious Diseases. 6th ed. Churchill Livingstone; 2005.
Mishra D. Cysticercosis headache: an important differential of childhood headache disorder in endemic countries. Headache. Feb 2007;47(2):301-2. [Medline].
Nash TE, Singh G, White AC, et al. Treatment of neurocysticercosis: current status and future research needs. Neurology. Oct 10 2006;67(7):1120-7. [Medline].
Pineda T, Eckstein C, Diethelm G, Cure J. Neurocysticercosis. Headache. May 2007;47(5):717-8. [Medline].
Salinas R, Prasad K. WITHDRAWN: Drugs for treating neurocysticercosis (tapeworm infection of the brain). Cochrane Database Syst Rev. 1999;(4):CD000215. [Medline].
Sandes AR, Mouzinho A, Valente P. Orbital cysticercosis: diagnosis and treatment controversies. Pediatr Infect Dis J. Feb 2007;26(2):180-1. [Medline].
Schantz PM. Tapeworms (cestodiasis). Gastroenterol Clin North Am. Sep 1996;25(3):637-53. [Medline].
Serpa JA, Moran A, Goodman JC, Giordano TP, White AC Jr. Neurocysticercosis in the HIV era: a case report and review of the literature. Am J Trop Med Hyg. Jul 2007;77(1):113-7. [Medline].
Serpa JA, Yancey LS, White AC Jr. Advances in the diagnosis and management of neurocysticercosis. Expert Rev Anti Infect Ther. Dec 2006;4(6):1051-61. [Medline].
Shandera WX, Kass JS. Neurocysticercosis: current knowledge and advances. Curr Neurol Neurosci Rep. Nov 2006;6(6):453-9. [Medline].
Sorvillo FJ, DeGiorgio C, Waterman SH. Deaths from cysticercosis, United States. Emerg Infect Dis. Feb 2007;13(2):230-5. [Medline].
Steinmann P, Zhou XN, Du ZW, et al. Tribendimidine and Albendazole for Treating Soil-Transmitted Helminths, Strongyloides stercoralis and Taenia spp.: Open-Label Randomized Trial. PLoS Negl Trop Dis. 2008;2(10):e322. [Medline].
Venkatesh R, Ravindran RD, Bharathi B, Sengupta S. Optic nerve cysticercosis. Ophthalmology. Nov 2008;115(11):2094. [Medline].
Wallin MT, Kurtzke JF. Neurocysticercosis in the United States: review of an important emerging infection. Neurology. Nov 9 2004;63(9):1559-64. [Medline].
Wani SA, Ahmad F, Zargar SA, Ahmad Z, Ahmad P, Tak H. Prevalence of intestinal parasites and associated risk factors among schoolchildren in Srinagar City, Kashmir, India. J Parasitol. Dec 2007;93(6):1541-3. [Medline].
Webbe G. Human cysticercosis: parasitology, pathology, clinical manifestations and available treatment. Pharmacol Ther. Oct 1994;64(1):175-200. [Medline].
Weisse ME, Raszka WV Jr. Cestode infection in children. Adv Pediatr Infect Dis. 1996;12:109-53. [Medline].
Further Reading
For more information, see the McGill Faculty of Medicine Web site images 16, 46, and 47. An interesting case is available at The Gorgas Course in Clinical Tropical Medicine and another at Partners.org.
Keywords
Taenia infection, appendicitis, beef tapeworm, cattle tapeworm, cerebral coenurosis, coenurosis, cysticercosis, edema, encephalitis, hemiparesis, hydrocephalus, intracranial hypertension, intracranial pressure, intraocular larva, muscular pseudohypertrophy, neurocysticercosis, NCC, ocular cysticercosis, papilledema, parasitic infections, pork tapeworm, pruritus ani, stroke, Taenia brauni, T brauni, Taenia multiceps, T multiceps, Taenia saginata, T saginata, Taenia serialis, T serialis, Taenia solium, T solium, taeniasis, taeniid infection
