Nematodes

• Nematodes


  Long, cylindrical, unsegmented
• Pseudocoele


  body cavity which contains all of the viscera (digestive, excretory, reproductive and nervous system.)
• DIGESTIVE SYSTEM - alimentary tract

  • Buccal cavity: provided with spines, hooks, cutting plates & teeth, has a complete alimentary tract
  • Esophagus: filariform, rhabditiform, spiruroid, strongyliform or stichosoma
• NERVOUS SYSTEM - With chemoreceptors

  • Acetyl choline – excitatory neurotransmitter
  • GABA (Gamma amino butyric acid) – inhibitory neurotransmitter Most nematocidal drugs interfere with neurotransmission that would cause the death of the parasite
  • AMPHIDS – pair of laterally placed minute receptors in the cephalic or cervical region of all nematodes
  • PHASMIDS – pair of lateral post-anal organs in species without caudal glands
• EXCRETORY SYSTEM

  Collecting tubules or canal Excretory pore
• NO CIRCULATORY SYSTEM

  Fluid in the body cavity

  • Hgb, glucose, proteins, salts & vitamins which fulfills the functions of the blood
• REPRODUCTIVE SYSTEM

  MALE: testes, vas deferens, seminal vesicle, ejaculatory duct, cloaca

  -Accessory copulatory apparatus:

  • Gubernaculum – wing-like appendage
  • Telamon
  • Copulatory spicule
  • Copulatory bursa – umbrella-like structure

  FEMALE: organs may be single or bifurcated o ovary, oviduct, seminal receptacle, uterus, ovijector and vagina

  -May be classified as:

  • Oviparous – lays the ova
  • Viviparous/larviparous – lays the larva 
  • Parthenogenetic
• Development Stage/LIFE CYCLE

  EGG

  • 3 LAYERS: Vitelline membrane, Chorionic or true shell, Albuminous covering
  • Nematodes with complete layers: Ascaris & Trichuris
  • 4 LARVAL STAGES
  • ADULT STAGE
• Mode of Attachment

  • Anchorage with attenuated ends (Trichuris trichiura)
  • Oral attachment to the mucosa (Ancylostoma)
  • Penetration of the tissues (Strongyloides)
  • Retention in the folds of the mucosa (Ascaris lumbricoides)
• MODES OF NOURISHMENT

  • Sucking with ingestion of blood (Ancylostoma)
  • Ingestion of lyzed tissues & blood (Trichuris)
  • Feeding of intestinal contents (Ascaris lumbricoides)
  • Body fluids (Filarial worms)
• LIFE SPAN

  1. Trichinella spiralis: 4-16 weeks
  2. Enterobius vermicularis: 1-2 months
  3. Ascaris lumbricoides: 12-17 months
  4. Hookworms: at least 14 years
  5. Filarial worms: up to 25 years
  6. Trichuris trichiura: 5-10 years
  7. Strongyloides stercoralis: 20-30 years
• APHASMIDIA - Lack “phasmids” or without caudal chemoreceptors


  SPECIES WHICH PARASITIZE THE SMALL INTESTINE

  1. Trichinella spiralis
  2. Capillaria philippinensis

  SPECIES WHICH PARASITIZE THE LARGE INTESTINE

  1. Trichuris trichiura
• PHASMIDIA - With “phasmids”


  SPECIES WHICH PARASITIZE THE SMALL INTESTINE

  1. Ascaris lumcricoides
  2. Necator americanus
  3. Ancylostoma duodenale
  4. Ancylostoma ceylanicum
  5. Strongyloides stercoralis

  SPECIES WHICH PARASITIZE THE LARGE INTESTINE

  1. Enterobius vermicularis

  SPECIES WHICH PARASITIZE THE TISSUES

  1. Wuchereria bancrofti
  2. Brugia malayi
  3. Loa loa
  4. Dracunculus medinensis

  SPECIES WHICH CAUSES LARVA MIGRANS IN MAN

  1. Ancylostoma braziliense
  2. Ancylostoma caninum
  3. Toxocara spp.