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  1. Cestodes, a class of the phylum Platyhelminthes, has 2 orders that infect humans: Cyclophyllidae and Pseudophyllidea. 
  2. One of the main differentiating points between the genera of the 2 orders is that the genera of the first order typically have a scolex with 4 suckers whereas the genera of the second order have a scolex with 2 opposing sucking grooves. 
  3. Another important point of differentiation is that Cyclophyllidae has 2 hosts in its life cycle whereas Pseudophyllidea requires 3. Taenia, Echinococcus and Hymenolepis are members of the order Cyclophyllidea.
  4. Longest tapeworm- D. latum (fish/broad tapeworm)
  5. Dwarf tapeworm- H.nana
  6. Rat tapeworm- H.diminuta
  7. Beef/unarmed tapeworm- T.saginata
  8. Pork tapeworm- T. solium



1.  Taenia Saginata-
  1. Beef tape worm, unarmed tape worm
  2. Habitat: scolex of the adult worm is embedded in the mucosa of the ileum
  3. Definitive host: man
  4.  Intermediate host: cow, buffalo
  5. Eggs/ gravid segments? passed in feces? cow/ buffalo swallow ? penetrate the gut wall? portal circulation? systemic circulation? muscle? cysticercus bovis? humans infected by eating uncooked beef? develop into adult worm? mating? eggs/ gravid segments
a.  Clinical features:
  1. Abdominal pain, diarrhea, constipation, intestinal obstruction
b.  Laboratory diagnosis:
  1. Proglottids/ eggs (spherical, bile stained, oncosphere): fecal examination
2.  Taenia Solium

i. Pork tape worm, armed tape worm

ii. Habitat: adult worm found in small intestine of man
iii. Definitive & intermediate host: man
iv. Intermediate host: pig
  • Eggs/ gravid segments? passed in feces? pig swallow ? penetrate the gut wall? portal circulation? systemic circulation? muscle? cysticercus cellulosae in pig? humans infected by eating uncooked pork? develop into adult worm? mating? eggs/ gravid segments
  • Man also acquires infection by ingesting eggs in contaminated food/ water, auto infection? larval form (cysticercus cellulosae) develops in humans (brain, eyes, subcutaneous tissue)
a.  Clinical features:
  1. Adult worm: abdominal pain, diarrhea, loss of appetite
  2. Cysticercus cellulosae (larva): may develop in any organ, in large numbers/ singly develop in subcutaneous tissues, muscles, brain, eye
  3. Neurocysticercosis( brain): epilepsy, hydrocephalus, increased intracranial tension, blurred vision
  • Commonest parasite of CNS in India/world
  • Second m/c cause of ICSOL
  • Symptoms due to dead and calcified larvae
  • Most common finding of neurocysticercosis on neuroimaging -calcification
b.  Laboratory diagnosis
  1. Proglottids/ eggs (spherical, bile stained, oncosphere): fecal examination
  2. Cysticercus cellulosae: biopsy, radiology (CAT scan, MRI), FNAC, serology (CFT, IHA, ELISA, IFAT)
B. Echinococcosis
  1. Dog tape worm
  2. Four species causing disease in humans
    1. granulosus (commonest)
    2. multilocularis (second most common) Causes alveolar echinococcosis/multilocular hydatid disease
    3. oligarthus (America)
    4. vogeli (latin America)
  3. Habitat: humans harbor the larval form (hyadtid cyst); adult worm in small intestine of dog & other canines
1.  Life cycle:
  1. Definitive host: dog, jackal, fox; adult worm resides in the small intestine & discharges eggs in the feces
  2. Intermediate host: sheep, pig, goat, cattle, man (dead end host)
  3. dog discharges eggs in feces? man acquires infection by ingestion of food/ water? hexacanth embryo hatches in duodenum? penetrates gut wall? portal circulation? systemic circulation? hydatid cyst (liver> lung> brain> kidneys> spleen) 
2.  Clinical features: pressure effects due to cyst, cerebral (epilepsy), renal (hematuria), rupture of cyst (allergic manifestation)
3.  Laboratory diagnosis
  1. Radiology: X-ray, CAT scan, MRI, IVP
  2. Casoni’s test: immediate hypersensitivity, I/D, wheal in 30 minutes
  3. Serology: IHA, CIEP( arc-5 test), ELISA, IFAT
C.  Hymenolepis Nana- Dwarf tape worm
  1. Habitat: adult worm found in ileum
  2. Mode of infection: food/ water contaminated with eggs, auto infection
  3. Life cycle: only tape worm for which humans act as both definitive & intermediate host
  4. Eggs ingested? oncosphere penetrates the intestinal villi? develop into cysticercoid stage? released in the lumen? reattaches to another villus? develops into adult worm? mating? eggs
  5. Clinical features: abdominal pain, diarrhea, weight loss
  6. Laboratory diagnosis:
    1. Eggs: fecal examination
    2. Adult worm/ proglottids: rarely see in feces

Fish acts as intermediate host in all except-
A. A.D. latum
B. C. sinensis
C. C.P. westermani
D. H.nana


Ans- D.

D. Diphyllobothrium Latum
  1. Fish tape worm/broad tape worm
  2. Habitat: adult worm found in small intestine
  3. Definitive host: man, dog, cat, pig
  4. First intermediate host: cyclops
  5. Second intermediate host: fresh water fish
  6. Operculated eggs liberated through feces of definitive host in water develops into ciliated embryo (coracidium) ingested by cyclops develops into second stage larva (procercoid) Cyclops containing procercoid larvae eaten by fish penetrates the gut wall liver/ muscle/fat develops into third stage larva (sparganum/ plerocercoid larva) man ingests infected fish in gut develops into adult worm mating eggs
1. Clinical features: Abdominal pain, diarrhea, megaloblastic anaemia called bothriocephalus anemia

2. Laboratory diagnosis:
  1. Segments of worm: fecal examination
  2. Egg: fecal examination
  3. Serology: ELISA, LA

In hydatid diseases intermediate host is: (AIIMS May 09)
A. Dog             
B. Man             
C. Cat              
D. Fox


Ans.  B. MAN

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