CLASS CESTODA

• Defining Characteristics

  • Scolex: anterior hooked attachment organ
  • Proglottids: body segments forming strobila
  • Loss of digestive tract: has nonciliated syncytial tegument with microtriches
  • Also called tapeworms
• REPRODUCTION

  • Sexual reproduction
  • Simultaneous hermaphrodite
  • Proglottid: to scatter eggs

  1. Eggs
  2. Oncosphere larva
  3. Cysticercus
  4. Adult
• Common tapeworms

  • Hymenolepis nana - dwarf tapeworm
  • Hymenolepis diminuta - rat tapeworm
  • Dipylidium caninum - dog tapeworm
  • Taenia solium - pork tapeworm
  • Taenia saginata - beef tapeworm
  • Diphyllobothrium latum - fish tapeworm
• HYMENOLEPIS NANA

  1. Embryonated egg in feces
  2. Egg ingested by insect
  3. Cysticercoid develops
  4. Embryonated eggs gets ingested by humans
  5. Oncosphere hatches cysticercoid develops in intestinal villus
  6. Scolex
  7. Adult in small intestine
  8. Eggs can be released through genital atrium or gravid proglottids disintegrates and gets passed in stools
  9. Autoinfection can occur if they remain in the intestine

  
• LIFE CYCLE of HYMENOLEPIS NANA

  • Egg
  • Oncosphere larva (hexacanth) hatches from egg and penetrates intestinal villus
  • Cysticercoid larva
  • Adult
• Hexacanth is the embryo of tapeworms for the subclass Cestoda, characterized by three pairs of hooks used for penetration through the gut of an intermediate host
• DIPYLIDIUM CANINUM

  • Host: domestic dogs, cats, children
  • Treatment: Praziquantel, Niclosamide
• Dipylidium Caninum

  • Each segment has 2 sets of male and female reproductive systems
  • Genital pore on each side
  • Scolex has a retractable pointed rostellum

  
• TAENIA SOLIUM

  • Infection
  • pork tapeworm infection, cysticercus cellulosae (larval stage/cysticercoid stage of Taenia)
• TAENIA SOLIUM

  • Life cycle
  • at copulation, cirrus of 1 worm is inserted into the partner's gonopore and sperm are ejaculated into the uterus
  • Gravid proglottids detach (apolysis) / eggs are passed in feces
  • Eggs contains oncosphere larva
  • Oncosphere: with scolex, travel to intestine an attach, absorb nutrient through tegument
  • Cysticercus: encyst and resting stage
• TAENIA SOLIUM

  • Etiology
  • ingestion of raw, frosted, undercooked meat
  • ingestion of egg in contaminated food or water
  • self-contamination
  • internal autoinfection (reverse peristalsis)
• TAENIA SOLIUM

  • Manifestations
  • vague abdominal discomfort
  • alternating diarrhea and cosntipation
• TAENIA SOLIUM

  • Detection
  • stool analysis
• TAENIA SOLIUM

  • Treatment
  • praziquantel, mebendazole, albendazole
• TAENIA SOLIUM

  
• Differences between T. solium and T. saginata

  • T. solium has 7-13 lateral arms while T. saginata has 15-20 letral arms
  • Scolex
  • T. solium
  • globular in outline and has four cicular suckers
  • has rostellum
  • has double row of alternating large and small hooklets
  • rostellar hooklets are shaped like daggers (armed scolex)
  • T. saginata
  • quadrate in outline and has four circular suckers
  • No rostellum and hooklets (unarmed scolex)

  
• DIPHYLLOBOTHRIUM LATUM

  • Adult is >10 meters, produces 3000 proglottids
  • Has a scolex with 2 bothria
• Diphyllobothrium latum

  • Life cycle
  • Egg
  • Oncosphere
  • Coracidium
  • Procercoid
  • Plerocercoid larvae (sparganum)
  • Adult

  Immature eggs are passed in feces
• Diphyllobothrium latum

  • Eggs mature 18-20 days and yield oncosphere which develops into a coracidia
  • After ingestion by a freshwater crustacean, the coracidia develops into a procercoid larvae
  • Following the ingestion, the procercoid larvae are released and migrates into the fish flesh where they develop into a plerocercoid larvae (sparganum) and this is the infective stage for humans
• Diphyllobothrium latum

  1. Embryonated eggs in feces
  2. Eggs embryonate in water
  3. Coracidia hatches and is ingested by crustaceans
  4. Procercoid larvae in body cavity of crustaceans
  5. Crustacean gets ingested by fish; Procercoid larva released from crustacean and develops into plerocercoid larva
  6. Predator fish ingests infected fish
  7. Human eats raw or undercooked infected fish