paraexam

• Cestodes

  Flatworms, segmented
• Helminths


  • Nemahelminthes (Roundworm)
  • Platyhelminthes (Flatworm)
• Trematode

  Fluke, flat, unsegmented
• Cestode

  Tapeworm, flat, segmented
• Types of helminths


  • Nematode
  • Trematode
  • Cestode
• Cestode


  • Flat dorsoventrally resembling a tape
  • Bilaterally symmetrical bodies
  • Segmented, with ribbon-like appearance
• Cestodes


  • Hermaphrodite
  • Both male and female reproductive organs in the same organism
  • Pair of lateral longitudinal nerves
  • No digestive tract
  • No circulatory system
• Habitat of Adult Cestode

  Intestine of the definitive host

  
• Intermediate host

  Larval stage encysted in the tissue
• Three Distinct Parts of Cestodes

  • Head or Scolex
  • Neck
  • Strobila
• Head or Scolex


  • Anterior structure
  • Main organ of attachment of the worm to the definitive host

  
• Rostellum

  Retractable, muscular, protruding part used for attachment, armed with hooks
• Suckers


  Used for attachment
• Neck


  • Region of growth and actively dividing
  • Segmentation or strobilization originates from the neck
• Strobila


  Long, segmented body composed of proglottids
• Types of Proglottids


  • Immature proglottids
  • Mature proglottids
  • Gravid proglottids
• Immature proglottid

  • Male and female reproductive organs are not yet differentiated
• Mature proglottid

  • Testes and ovaries are differentiated and prominent
• Gravid proglottid

  • Uterus with lateral branches is filled with eggs
• Two Medically Significant Cestodes

  • Pseudophyllidea
  • Cyclophyllidea
• Pseudophyllidea


  • Scolex is spatulate with 2 slit-like sucking grooves (bothria)
  • Intermediate host is two
  • Genital pores are midline
  • Uterus is midline, non-branching, rosette-like
  • Uterus has a uterine pore
  • Proglottids are anapolytic
  • Ova are immature, operculated
• Cyclophyllidea


  • Scolex is globular with 4 muscular cup-shaped suckers with or without rostellum with hooks
  • Intermediate host is one or none
  • Genital pores are lateral
  • Uterus has lateral branches and no uterine pore
  • Proglottids are apolytic
  • Ova are non-operculated with hexacanth embryo
• Types of Larva


  • Bladder Larva (Cysticercus, Cysticercoid, Hydatid cyst, Coenurus)
  • Solid Larva (Coracidium, Procercoid, Plerocercoid)
• Cysticercus

  Larva of Taenia solium, Taenia saginata
• Cysticercoid

  Larva of Hymenolepis spp.
• Hydatid cyst

  Larva of Echinococcus spp.
• Coenurus

  Larva of Taenia multiceps
• Coracidium

  First stage larva of Diphyllobothrium latum
• Procercoid

  Second stage larva of Diphyllobothrium latum
• Plerocercoid (Sparganum)


  Third stage larva of Diphyllobothrium latum
• Diphyllobothrium latum


  • Adult is 3-10 meters in length with 4,000 proglottids
  • Has 2 bothria or sucking grooves
  • Definitive host is humans
  • Intermediate hosts are copepod Cyclops or Diaptomus, and fish
  • Diagnostic stage is operculated ova
  • Infective stage is plerocercoid larva
  • Paratenic host is predator fishes

  
• Diphyllobothrium latum scolex


  • Has 2 bothria, no acetabula and rostellum (suckers)
• Diphyllobothrium latum proglottid


  • Uterine pore is in the middle to discharge eggs
  • Genital pores are midline where semen is drained and transferred to vagina and ovary
• Diphyllobothrium latum gravid proglottid


  • Uterus is rosette-shaped in the midline
• Diphyllobothrium latum ova


  Operculated ova with terminal knob at the posterior end
• Pathogenesis of Diphyllobothrium latum


  • Infection is usually just one worm
  • Can cause mechanical obstruction if there are a large number of worms
  • Some patients are asymptomatic
  • Competes with Vitamin B12 with the host leading to Vitamin B12 deficiency and megaloblastic anemia

  
• Diagnosis of Diphyllobothrium latum is by demonstration of egg and at some occasion the proglottid in stool sample

  
• Treatment of Diphyllobothrium latum

  • Drug of choice is Praziquantel
  • Cure is recovery of scolex and negative operculated ova after three months of treatment
• Trematodes


  Fluke, flat, unsegmented

  
• Taenia solium


  • Common name is Pork Tapeworm
  • Definitive host is humans
  • Intermediate host is pigs
  • Diagnostic stage is egg
  • Infective stage is cysticercus cellulosae
  • Habitat is upper small intestine
  • Autoinfection is possible