Microbiology & infectious diseases

Parasites and prion-CNS

Taenia solium (neurocysticercosis)



Last author update: 1 January 2015
Last staff update: 10 November 2023

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PubMed Search: Taenia solium cestodes

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 February 23rd, 2024.
Definition / general
  • Tapeworm infections were first reported in 1500 B.C. and are considered one of the earliest human parasites
Epidemiology
  • 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
Reservoirs
  • 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

Contributed by Wikipedia
Taenia solium adult

Taenia solium adult



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Life cycle

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
Transmission
  • 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
Diagnosis
  • 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
Radiology images

Contributed by Centers for Disease Control and Prevention
MRI

MRI

Case reports
Treatment
  • 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
Microscopic (histologic) images

Contributed by Centers for Disease Control and Prevention and Wikipedia
Brain tissue

Brain tissue

Cysticercus

Cysticercus

Taenia solium scolex

T. solium scolex

Egg of T. solium

Egg of T. solium

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