PARA LEC PART 2 EXAM

• Medically important groups

  • Cestodes (Tapeworms)
  • Trematodes (Flukes)
• Flatworms


  • Collectively called the FLATWORMS
  • Dorsoventrally flattened, bilaterally symmetrical
  • Covered by a membrane called tegument
  • Hermaphroditic except for Schistosoma sp.
• Schistosoma

  A trematode
• Classes Cestoda and Trematoda

  Contain species parasitic to humans
• Cestodes

  • Flat, segmented body with various length
  • Hermaphroditic with each proglottid developing both male and female reproductive organs
  • No circulatory system
  • No digestive tract
  • Diagnosed by finding eggs or proglottids in the feces
• Cestodes

  • MICROTRICHES - outward projections similar to microvilli of gut mucosal cells, increase surface area for nutrient absorption, interdigitate with host microvilli
• Cestodes


  Can absorb nutrients through Microtriches present in the tegument, causing an increase in surface area for nutrient absorption
• Habitat of adult tapeworm: intestine of the Definitive host
• Intermediate host: larval stage encysted in the tissue
• Mnemonics for general characteristics

  • Taenia species (example)
  • Adult worms are seen in the intestine
  • Proglottids contain male and female parts
  • Eggs have 6 hooked embryos
  • World-wide distribution
  • No respiratory, vascular, or digestive system
  • Ribbon-like body, flat
  • Middle (intermediate host is required)
• Scolex


  For attachment: Rostellum armed with hooks, Suckers
• Scolex


  • Head of the parasite; cestodes will adhere to the mucosa via the scolex, armed with hooks or suckers, rostellum present in the scolex of unarmed tapeworms, suckers for absorption of nutrients
• Neck

  Germinal portion connecting the scolex to the strobila, shortest part of the body consisting of immature proglottids, produces proglottids
• Strobila

  1. Immature proglottids, Mature proglottids, Gravid proglottids

  2. Segments bud from behind the scolex and are immature

  3. As they are pushed back, they mature, and fill with eggs

  4. Once eggs are fertilized, they become “gravid” proglottids
• Immature proglottids

  • Reproductive organs are undifferentiated
  • Might not see any structures
• Mature proglottids

  • Reproductive organs are differentiated
  • The dark portion are the testes. The portion that looks like a kidney shape are your ovaries
• Gravid proglottids


  • Uterus with lateral branches filled with eggs
  • Presence of genital pore
  • Once it is already in a gravid portion, you will have difficulty identifying whether that is already a uterus or an ovary because the ovaries and testes start to disintegrate so what is left is your uterus
• The parasite in the picture is called unarmed because it does not have hooklets
• There might be cestodes that do not have any rostellum or do not have hooklets at all
• Species which require a vertebrate intermediate host

  • Taenia solium (pork tapeworm)
  • Taenia saginata (beef tapeworm)
  • Echinococcus granulosus (dogs, carnivores)
• Species which require an invertebrate intermediate host

  • Dipylidium caninum (dog tapeworm, double-pored tapeworm)
  • Hymenolepis diminuta (rat tapeworm)
  • Raillietina garrisoni
• Species which may or may not require intermediate host

  • Hymenolepis nana (dwarf tapeworm)
• Species which infect man in their larval stages

  • Echinococcus granulosus (hydatid worm)
  • Echinococcus multilocularis
  • Taenia solium
  • Diphyllobothrium latum
• Binomial name and common name

  • Taenia saginata - Beef Tapeworm
  • Taenia solium - Pork Tapeworm
  • Taenia multiceps - Coenurus Tapeworm
  • Echinococcus granulosus - Hydatid Tapeworm
  • Echinococcus multilocularis - The Multiloculate or Alveolar Hydatid Tapeworm
  • Hymenolepis nana - Dwarf Tapeworm
  • Hymenolepis diminuta - Rat Tapeworm
  • Dipylidium caninum - Double-pored Tapeworm
  • Diphyllobothrium latum - Broad Fish Tapeworm
• Classification

  • Pseudophyllidean
  • Cyclophyllidean
• Pseudophyllidean

  • Diphyllobothrium latum
  • Spirometra: S. erinacei ; S. mansoni ; S. ranarum
• Cyclophyllidean

  • Taenia solium and Taenia saginata
  • Hymenolepis nana and Hymenolepis diminuta
  • Dipylidium caninum
  • Raillietina garrisoni
  • Echinococcus granulosus
• Comparison of Scolex in Pseudophyllidean and Cyclophyllidean

  • Scolex in Pseudophyllidean: Almond/ Spatulate, 2 slit-like grooves
  • Scolex in Cyclophyllidean: Globular, 4 cup-like suckers
• Comparison of Uterus in Pseudophyllidean and Cyclophyllidean

  • Uterus in Pseudophyllidean: No branching, with pores
  • Uterus in Cyclophyllidean: Branching, blind sac
• Comparison of Uterine pore in Pseudophyllidean and Cyclophyllidean

  • Uterine pore in Pseudophyllidean: Present
  • Uterine pore in Cyclophyllidean: Absent
• Comparison of Genital pore in Pseudophyllidean and Cyclophyllidean

  • Genital pore in Pseudophyllidean: Ventral, in the midline
  • Genital pore in Cyclophyllidean: Lateral
• Comparison of Eggs in Pseudophyllidean and Cyclophyllidean

  • Eggs in Pseudophyllidean: Operculated, gives rise to ciliated larvae
  • Eggs in Cyclophyllidean: Not operculated, do not give rise to ciliated larvae
• Comparison of Intermediate Host in Pseudophyllidean and Cyclophyllidean

  • Intermediate Host in Pseudophyllidean: 2
  • Intermediate Host in Cyclophyllidean: 1 or none
• Genital pore location

  • Ventral, in the midline
  • Lateral
• Eggs characteristics

  • Operculated, gives rise to ciliated larvae
  • Not operculated, do not give rise to ciliated larvae
• Intermediate Host characteristics

  • 2
  • 1 or none
• Apolysis

  1. Anapolytic

  2. Apolytic
• Anapolytic: 'your proglottid are not shed off because of the presence of uterine pore; they do not need to detached from the tapeworm'
• Apolyitc: 'they do not have uterine pore, they have the blind sac. To release the eggs, it is by means of gravid proglottids which detaches from the tapeworm and present in our feces'
• DIPHYLLOBOTHRIUM LATUM