CESTODES

• THE CESTODES (FLATWORMS)

  Basic Parts of a Cestode

  1. Scolex the anterior (front) end of a tapeworm, with hooks
  2. Mature segment uterus, ovary, testes, sperm duct, and a 

                                           genital pore.

  • Gravid segment uterine branches carrying eggs

  
• THE CESTODES (FLATWORMS)

  A) Scolex

  B) Mature Segment

  C) Gravid segment

  
• Order of Cestodes

  Pseudophyllidean

  • Diphyllobothrium latum

  Cyclophyllidean

  Requires vertebrate IH

  • Taenia solium
  • Taenia saginatta

  Requires invertebrate IH

  • Dipyllidium caninum
  • Hymenolepis diminuta
  • Raillietena garrisoni

  May or may not require IH

  • Hymenolepis nana

  Infects man in the larval stage

  • Echinococcus species
• Pseudophyllidean

  • SCOLEX – Spatulate with two sucking grooves 
  • OVA – operculated, immature 
  • EMBRYO – coracidium (ciliated)
  • 2 INTERMEDIATE HOSTS
  • Procercoid (1st IH)
  • Plerocercoid/Sparganum (2nd IH)

  
• Cyclophyllidean

  • SCOLEX – Globular with 4 muscular suckers
  • OVA – non-operculated,  mature
  • EMBRYO – hexacanth/oncosphere
  • 1 INTERMEDIATE HOST 
  • Cysticercus – Taenia
  • Cysticercoid – Raillietina, Hymenolepis, Dipylidium
  • Hydatid Echinococcus

  
• Diphyllobothrium latum (BroadFish Tapeworm)

  General Morphology: (8 to 12 meters long)

  • SCOLEX: spatulated and elongated with bothria, two elongated longitudinal grooves
  • MATURE PROGLOTTID: broader than long, rosette appearance, and numerous testes in the lateral fields
  • EGGS/OVUM: operculated/ immature
• Diphyllobothrium latum

  
• Diphyllobothrium latum

  CN: Fish tapeworm, broad tapeworm

  1st IH: Copepod (Cyclops)

  2nd IH: Freshwater fish

  Disease: 

  Diphyllobothriasis (Vit. B12 deficiency causing macrocytic anemia)

  Sparganosis (larval infection, ingestion of procercoid larva, “measly pork”)

  Diagnosis:

  Demonstration of ova in stool, not the segments because no apolysis
• Taenia saginata (Beef Tapeworm)

  General Morphology: (1,000 to 2,000 segments)

  • SCOLEX: no hooks (unarmed 4 suckers)
  • PROGLOTTID (Uterine branches): 23 (14-32)
  • EGGS/OVUM: spherical, with radial striations 

  (not infective to man, indistinguishable)
• Taenia saginata (Beef tapeworm)

  
• Taenia saginata

  CN: Beef Tapeworm

  Infective Stage: Cysticercus bovis

  Passing of proglottids: single, spontaneous

  Definitive Host: man

  Intermediate Host: cattle, reindeer

  MoT: eating of improperly cooked meat, littered human feces, and poor meat inspections
• Taenia solium (Pork tapeworm)

  General Morphology: (800 to 1,000 segments)

  • SCOLEX: hooks (armed 4 suckers)
  • PROGLOTTID: (Uterine branches): 23 (14-32)
  • EGGS/OVUM: spherical, with radial striations

  (6 hooklets, infective, matures into larva)
• Taenia solium (Pork tapeworm)

  
• Taenia solium

  CN: Pork tapeworm

  Infective Stage: Cysticercus cellulosae (thin walled bladder within a single scolex develops)

  Passing of proglottids: apolysis in chains/groups, passively

  Definitive Host: man

  Intermediate Host: pig, wild boar

  MoT: eating of improperly cooked meat, littered human feces, and poor meat inspections

  Pathology: Cysticercus of T. solium can travel towards the brain and inside the eye.

  Diagnostic Test

  Taeniasis: Stool sample is repeated three times 

  • Visualize uterine branches of gravid proglottids with India ink injection 
  • Scolex examination
• Hymenolepis nana (Dwarf tapeworm, Vampirolepis nana)

  MOST COMMON tapeworm in people and can complete its life cycle in a single host

  General Morphology: 

  long and slender neck, wider than large, unilateral genital pores

  • SCOLEX: 4-cup shaped suckers, retractable rostellum, 20-30 Y-shaped hookletss
  • EGG: 2 polar thickenings with 4-8 filaments

  Either direct or indirect life cycle
• Hymenolepis nana (Dwarf tapeworm, Vampirolepis nana)

  
• Hymenolepis nana

  CN: Dwarf tapeworm, Vampirolepis nana

  Intermediate Host: Dual pathway life cycle (man to man without IH) + Fleas, beetles

  Definitive Host: man, rats

  Habitat: Small intestine

  Pathogenesis: Asymptomatic but DEADLY in immunocompromised

  Diagnosis: Detection of egg in feces (6-hooked oncosphere)
• Hymenolepis diminuta (Rat tapeworm)

  General Morphology: bigger than H. nana

  • SCOLEX: 4 suckers, rostellum, NO hooklets

  EGG: 2 polar thickenings without polar filam
• Hymenolepis diminuta (Rat tapeworm)

  
• Hymenolepis diminuta

  CN: Rat tapeworm

  Habitat: Also small intestine

  Definitive Host: rats

  Intermediate Host: Fleas, beetles, cockroaches

  Diagnosis: Demonstration of egg in stool
• Dipylidium caninum (Dog tapeworm, double-pored tapeworm)

  General Morphology: 

  • SCOLEX: rhomboid with 4 suckers, apical rostellum, 1-7 rows of spines
  • STROBILA: 2 set of reproductive organs
  • GRAVID SEGMENTS: “Pumpkin-seed”, 2 bilateral genital pores
  • ADULT: 60 cm x 3mm (length x width)
  • EGG: 20-40 micra in diameter for the egg capsules
• Dipylidium caninum (Dog tapeworm, double-pored tapeworm)

  
• Dipylidium caninum

  CN: Dog tapeworm, double-pored tapeworm

  Infective stage to DH: Cysticercoid larvae

  Definitive Host: Dogs and cats

  Intermediate Host: Fleas and beetles

  MoT: ingestion of infected fleas

  Habitat: Flour beetles. Fleas
• Scientific name: Echinococcus granulosus

  Common name: Hydatid worm 

  Infective stage: Embryonated ova in feces

  Diagnostic stage: Hydatid cyst

  MOT: Ingestion of embryonated ova

  IH: Sheep and other herbivore animals

  DH: Dog and other canine animals
• Echinococcus granulosus (Hydatid worm)

  Other species: E. vogeli, E. multilocularis

  General Morphology: SHORTEST CESTODE (0.25 to 0.9 cm in size)

  • SCOLEX: pyriform shape with rostellum and hooks
  • 3 segments: immature, mature, and gravid
  • OVA: subspherical shape, brown striated

  oncosphere, resembles Taenia spp. ova

  • LARVA: “Hydatid Cyst
  • 2 layers: outer laminated layer and germinal layer

  inner germinal layer

  “Hydatid sand” - free brood capsules and free scolices
• Echinococcus granulosus (Hydatid worm)

  Diseases: Unilocular echinococcosis, echinococcus disease, hydatid disease

  Pathology: Cystic echinococcosis, cysts can also rupture

  Diagnosis: Biopsy, Ultrasound, MRI, CT Scan, 
• Raillietina garrisoni

  CN: Rat Tapeworm

  MoT: Ingestion of cysticercoid larvae in flour beetles