Nematoda

• What is the process wherein nematodes molt cuticle?


  Ecdysozoa
• What is ecdysozoa?


  • it is the molting of cuticle with growth
  • no common body plan between members
• What regulates ecdysozoa?

  ecdysone
• Nematoda comes from the word?

  Nemata, nematos (thread)
• Nematodes have a blank covering?


  cuticle covering
• What do nematodes lack?

  they lack motile cilia/flagella
• Nematodes may be?


  they may be free living or parasitic. some species may parasitize humans
• what is the important model organism of nematode?

  caenorhabditis elegans
• What is the body plan of nematodes?

  • they have a complete digestive system
  • they do not have circulatory and respiratory systems
  • they are dioecious
  • males with copulatory spicules
  • direct development
• Intestinal or Giant Roundworm or Ascaris lumbricoides Linnaeus

  • oral-fecal route transmission
• The cycle of Ascaris lumbricoides

  1. adults in small intestine
  2. unfertilized egg (will not undergo further development), fertilized egg
  3. embryonated egg with L3 larva
  4. ingestion of embryonated eggs
  5. hatched larvae enters circulation and migrate to lungs
  6. larvae are coughed up and swallowed, re-entering the gastrointestinal tract. Maturation proceeds in the small intestine.
• Hookworms, Ancyclostoma duodenale, Necatory americanus

  • cutting plates pinch off intestinal mucosa
  • path of worms may be visible from the outside
• The cycle of intestinal hookworm

  1. eggs in feces
  2. rhabditiform larva hatches
  3. development to filariform larva in the environment
  4. filariform larva penetrates skin
  5. adults in small intestine
• Pork worm, Trichinella spiralis

  • ingestion of infected meat
  • typically pork
  • widespread
• The cycle of pork worm

  1. ingestion of undercooked meat
  2. larva released in small intestine
  3. adults in the small intestine
  4. larva depoisted in mucosa
  5. encysted larva in striated muscle
• Pinworm, enterobius vermicularis

  • most common nematode parasite in US
  • gravid female migrates to the perianal region at night to lay eggs - tape test
• What is the most common nematode parasite in US?


  pinworm
• The cycle of pinworm

  1. eggs on perianal folds
  2. embryonated eggs ingested by human
  3. larvae hatch in the small intestine
  4. adults in lumen of cecum
  5. gravid female migrates to perianal region at night to lay eggs
• Guinea worm, Dranculus medinensis

  • endemic in 5 african countries
  • drinking unfiltered water containing copepods infected with the worm
• The cycle of guinea worm

  1. human drinks unfiltered water (1a)
  2. infective copepods ingested by fish, frogs, or other aquatic animals (1b)
  3. larvae released when copepods die. larvae peentrate the host's stomach and intestinal wall. they mature and reproduce in the subcutaneous tissues
  4. fertilized female worm migrates to surface of skin, causes a blister, and discharges larvae
  5. L1 larvae released into water from the emerging female worm
  6. L1 larvae consumed by a copepod
  7. Larvae undergoes two molts in the copepod and becomes a L3 larvae.
• Human whipworm, trichuris trichiura
• The cycle of human whipworm

  1. unembryonated eggs passed in feces
  2. 2-cell stage
  3. advanced cleavage
  4. embryonated eggs are ingested
  5. larvae hatch in small intestine
  6. adults in cecum
• Causative Agent of Elephantiasis, wunchereria bancrofti seurat
• The cycle of Elephantiasis

  1. mosquito takes a blood meal
  2. adults in lymphatics
  3. adults produce sheathed microfilariae that migrate into lymphatic and peripheral blood circulation
  4. mosquito takes a blood meal
  5. microfilariae shed sheaths, penetrate mosquito's midgut, and migrate to thoracic muscles
  6. L1 larvae
  7. L3 larvae
  8. migration to mosquito head and proboscis
• Eye worm, loa loa
• The cycle of loa loa (eye worm)

  1. fly takes a blood meal
  2. adults in subcutaneous tissue
  3. adults produce sheathed microfilariae that are found ins pinal fluid, urine, sputum, peripheral blood, and in the lungs
  4. fly takes a blood meal
  5. microfilariae shed sheaths, penetrate fly's midgut, and migrate to thoracic muscles
  6. L1 larvae
  7. L3 larvae
  8. migrate to head and fly's proboscis
• What is the largest nematode?

  placentonema gigantissima
• What is placentonema gigantissima?

  • it is the alrgest nematode
  • female P. Gigantissima can grow up to 8.4 meters long
  • males up to 3.9m long
  • it infects the placenta of female sperm whales