Microbiology, parasitology & COVID-19


Taenia solium (neurocysticercosis)

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PubMed Search: Taenia solium[TI] cestodes free full text[sb]

Haind Fadel, M.D.
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Cite this page: Fadel H. Taenia solium (neurocysticercosis). PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/parasitologytaeniasolium.html. Accessed March 22nd, 2023.
Definition / general
  • Tapeworm infections were first reported in 1500 B.C. and are considered one of the earliest human parasites
  • United States:
    • Not a public health threat; infection has a specific and limited distribution
    • ~1,000 cases occur per year, usually in Latin American immigrants in major urban centers with large immigrant populations (Chicago, Los Angeles, New York City)
  • Worldwide:
    • 50 million people are affected, 50,000 die annually, mainly from complications of cysticercosis
    • Highest incidence in Central South America (some regions of Mexico have 4% prevalence) and Africa
    • Also prevalent in Southeast Asia, India, Philippines, China, Eastern Europe
  • Two known reservoirs of T. solium are pigs and humans
  • Humans serve as the definitive host; pigs serve as primary intermediate host
  • Less common hosts are cats, dogs, primates, sheep
Diagrams / tables

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Life cycle

Classification of T. solium

Kingdom Animalia
Phylum Platyhelminthes
Class Cestoida
Order Cyclophyllidea
Family Taeniidae
Genus Taenia
Species solium
Clinical features
  • T. solium infection can progress to a disease state in 10 days or as slowly as 10 years
  • Taeniasis:
    • Typically, adult tapeworm does not produce eggs in stool (taeniasis) for 8 - 12 weeks
    • Most intestinal infections are asymptomatic but some patients exhibit abdominal pain, anorexia, malaise, weight loss, megaly (brain, eye, heart)
    • Common complications include appendicitis, obstruction of bile ducts / pancreatic ducts, ectopic tapeworm growth, mild eosinophilia
  • Neurocysticercosis:
    • 3 common symptoms: convulsions / seizures, intracranial hypertension, psychiatric disturbances
    • Common sites are subcutaneous tissue, eye, brain
  • Consumption of raw / undercooked pork products
  • Human to human or pig to human transfer of T. solium eggs through direct contact with feces
  • Human to human or pig to human transfer of T. solium eggs through consumption of food / water containing fecal matter (indirect)
  • Autoinfection
  • Made by finding eggs in stool (using direct or concentration techniques) or in perianal folds (using cellophane tape technique)
  • Eggs are spherical and measure 31 - 43 μm in diameter
Case reports
  • Treament with anthelimintic drugs is often sufficient to eliminate the parasite
  • Treatment of choice is single dose of praziquantel (5 - 10 mg/kg)
  • Praziquantel acts by increasing the permeability of the cell membrane, resulting in a efflux of intracellular calcium, leading to muscle tetany and the eventual paralysis and elimination of the worm
  • In cases of taeniasis, praziquantel is close to 100% effectiveness
  • Must also examine stools weekly for gravid proglottids for 5 weeks, to ensure clearance of parasite
Neurocysticercosis treatment
  • Much more complicated than treatment for taeniasis; often tailored to each patient
  • Either surgical intervention or an anthelmintic drug (i.e. praziquantel)
  • If an anthelmintic agent is used, a glucocorticoid is also prescribed to relieve the inflammation caused by the death of cysticerci in organ tissue
Microscopic (histologic) description
  • Proglottids of taeniids have a characteristic lateral protrusion known as the genital pore
  • Careful injection of India ink through the genital pore, using a tuberculin needle and syringe, may outline the uterus
  • The gravid uterus of T. saginata has 15 - 20 lateral branches compared to 7 - 13 for T. solium
  • Proglottids may be cleared overnight in glycerol or stained with carmine or hematoxylin using published procedures
  • If recovered, the scolex of T. solium has four suckers and a hook on the crown or rostellum
  • Shell is thick, radially striated and contains a six hooked embryo
  • Eggs of all Taenia species are indistinguishable and should be reported only as Taenia eggs
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