Cestodes

• Tapeworms


  Known as 'tapeworms'
• Tapeworms


  • They have an extensive size variation: 3mm – 10m
  • They generally require intermediate hosts
  • Their method of growth involves addition of segments (proglottids)
  • Each proglottid, when mature, produces infective eggs for the intermediate host
  • The anterior headlike segment are known as scolex
  • The scolex has suckers
  • Some species have hooklets on their scolex as a means of attachment to intestinal mucosa
  • Their necks are directly behind the scolex
  • Treatment is targeted at detaching the scolex from the mucosa because the neck area is where proglottid production occurs
  • Gravid proglottids at the distal end of the organism discharge eggs into the feces
  • Most tapeworm eggs contain hexacanth embryo or oncospheres
  • Transmission to humans is through ingestion of their larval stage, known as cysticercus, cysticercoid, or plerocercoid larva
  • Diagnosis is done by finding the eggs in feces
  • Proglottids can be used if intact when passed through feces
• Tapeworms


  • Flat and ribbon-like
  • White yellow-ish in color
  • Segmented
  • Monoecious (hermaphroditic and partially parthenogenic)
  • No gastrointestinal tract
  • No circulatory system
  • Has well-developed reproductive organs
  • Has tegument
• Tapeworm eggs


  Generally non-operculated and mature/embryonated
• Scolex


  • Attachment organ (to the lining of the small intestine)
  • SHAPE – globular, pyriform, spoon-like (spatulate-shaped only in D. latum)
  • MAJORITY – with 4 cup-like suckers/grooves/acetabulum
  • Recovery of the scolex indicates success of treatment
  • Rostellum - Fleshy extension of scolex (crown area), May be armed or unarmed
• Neck


  • Region of growth, Location of germination process, Point of proliferation for the next set of segments, The segments nearer to the neck are the younger segments, the ones farther are the older segments
• Proglottids


  • Each segment, STROBILA – chain of proglottids/segments, IMMATURE – nearest to the neck, MATURE – middle portion; this is where the reproductive structures are formed and found, GRAVID/RIPE – farthest from the neck, Filled with eggs (in the uterus), Can be detached through apolysis
• Pseudophyllidea


  Known as 'false tapeworms'
• Cyclophyllidea


  Known as 'true tapeworms'
• Diphyllobothrium latum is the largest tapeworm of man
• Diphyllobothrium latum


  New name is Dibothriocephalus latus
• Diphyllobothrium latum


  • Common names: Broad fish tapeworm, Broad tapeworm, Fish tapeworm
  • Habitat: Small intestine
  • Diagnostic stage: Egg/scolex (because only this parasite has a spatulate scolex)
  • Infective stage: Plerocercoid larva
  • 1st Intermediate host: Copepods (cyclops, diaptomus)
  • 2nd Intermediate host: Freshwater fish (small fishes)
  • Paratenic host: Carnivorous fishes
  • Larval stages: Coracidium -> Procercid -> Plerocercoid
  • Mode of transmission: Ingestion
  • Treatment: Praziquantel
  • Prevention: Freezing of fishes (-18°C for 24-48 hours), Proper cooking of fishes (50°C for 10 minutes)
  • Eggs: 1 million eggs/ova per day, Non-embryonated, Operculum on one end with terminal knob (abopercular knob) on the other end, With underdeveloped coracidium, Mistaken with P. westermani eggs
  • Adults: Lifespan is 25 years, Length: 3-5 meters to 10 meters, Mistaken for Spriometra, Scolex: Spatulate/spoon/almond shaped, With 2 bothrium (slit-like sucking organ), Uterus: Rosette-like appearance, Strobila: Up to 4000 proglottids, Have uterine pore aside from the genital pore
• Laboratory Diagnosis for Diphyllobothrium latum


  Stool exam: DFS, Kato-katz, Look for eggs or scolex

  Examination for gastric juice: Free hydrochloric acid, To differentiate Diphyllobotriasis from Pernicious anemia
• Taenia spp.


  • T. saginata - Beef tapeworm, Unhooked tapeworm

  T. solium - Pork tapeworm, Hooked tapeworm

  Habitat: Small intestine

  Intermediate host: Cattle, cows, camels (T. saginata), Pigs, man (T. solium)

  Larval stage: Cysticercus bovis (T. saginata), Cysticercus cellulosae (T. solium)

  Infective stage: Cysticercus bovis (T. saginata), Cysticercus cellulosae and embryonated egg (T. solium)

  Mode of transmission: Ingestion of measly beef with infective larva (T. saginata), Ingestion of measly pork with embryonated egg (T. solium)

  Pathology: Taeniasis saginata (due to adult), Taeniasis solium (due to adult), Cysticercosis (due to larva)

  Treatment: Praziquantel, Niclosamide
• Laboratory Diagnosis for Taenia spp.


  Stool exam: Direct fecal smear, concentration techniques (sedimentation), Look for eggs, proglottids, scolex
• When laid/deposited


  • ✓
• Has 6 hooklet paris


  • ✓
• Motile (the eggs are called 1st stage larva due to their motility/movement)


  • ✓
• Their eggs are indistinguishable from each other


  • ✓
• Adults may lay 594,000 ova per year


  • ✓
• T. saginata


  Causes Taeniasis saginata
• Symptoms of Taeniasis saginata


  • Non-specific symptoms – epigastric pain, hunger pangs, weakness, weight loss, loss of appetite, pruritus ani
  • Intestinal obstruction due to tangled proglottids
• T. solium


  • Due to adult – Taeniasis solium
  • Due to larva – Cysticercosis
• Symptoms of Taeniasis solium


  • Abdominal discomfort, hunger, malabsorption
• Symptoms of Cysticercosis


  • Accidental ingestion of egg
  • More dangerous than Taeniasis solium
  • Can spread to other organs (if it migrates to the brain, it is neurocysticercosis, the most common parasitic CNS disease and the most serious manifestation; it may lead to death)
• Stool exam methods


  • Direct fecal smear
  • Concentration techniques (sedimentation)
  • Look for eggs, proglottids, scolex
• Presence of eggs in stool is intermittent


  • ✓
• Eggs are just recorded as Taenia spp. because they're indistinguishable


  • ✓
• Double slide compression method

  1. Sample: Gravid proglottids

  2. Demonstration of lateral branches in the proglottids

  3. Gravid proglottid is placed between two glass slides and the lateral branches are observed
• India ink stain


  1. Black stain

  2. Used to visualize the lateral branches in the proglottids of Taenia spp.

  3. Observes the genital pore (lateral) which are connected to the uterus, once stained, the branches are easier to view
• Perianal swab


  Eggs may be left in the perianal region as stool is passed
• A patient positive for Taenia spp. must practice proper hygiene because of the possible medical complications that may arise from the infection
• Taenia asiatica


  • Old name is Taiwan Taenia spp.
  • Third specie of Taenia
  • Closely resembles T. saginata
• Asian Taenia spp.


  Other name: Taenia saginata asiatica
• Intermediate host


  • Pigs, cattle, goats, wild boar, monkeys
• Larval stage


  Cysticercus viscerotropica
• Other Taenia spp.


  • T. multiceps
  • T. serialis
  • T. brauni
  • T. glomerata
• T. multiceps


  • Other name: Multiceps multiceps
  • Common name: Bladder worm
  • Habitat: Eyes, brain
  • Larval stage: Coenurus larva (a unilocular encysted larva)
  • Infective stage: Eggs
  • Intermediate host: Sheep
  • Final host: Canids
• T. serialis


  • Common name: N/A
  • Habitat: Subcut. tissue
  • Larval stage: Coenurus larva (a unilocular encysted larva)
  • Infective stage: Eggs
  • Intermediate host: Rabbits
  • Final host: Dogs, foxes
• T. brauni


  • Common name: N/A
  • Habitat: N/A
  • Larval stage: Coenurus larva (a unilocular encysted larva)
  • Infective stage: Eggs
  • Intermediate host: Herbivores
  • Final host: N/A