Filarial Worms

• What phylum do nematodes belong to?

  Phylum Nemathelminthes (Nematoda)
• Why are nematodes considered the most worm-like of all helminths?

  Because they resemble the common earthworm appearance.
• What does the name "nematode" mean?

  "Nema" means thread.
• Where can free-living nematodes be found?

  In soil and water.
• What is the shape of nematodes?

  They are elongated, cylindrical or filariform in shape.
• What are the sensory organs of nematodes?

  Amphids (anterior) and phasmids (posterior).
• What is the function of amphids in nematodes?

  They serve as chemoreceptors.
• Where are phasmids located in nematodes?

  At the posterior part or caudal portion of the parasite.
• How do nematodes move?

  By contraction of the longitudinal muscles.
• What are the layers of the nematode body wall?

  Outer cuticle, middle hypodermis, and inner somatic muscular layer.
• What is the sexual characteristic of nematodes?

  They are dioecious (separate sexes).
• How does the male nematode differ from the female?

  The male is generally smaller and has a curved or coiled posterior end.
• What are the reproductive methods of female nematodes?

  They may be oviparous, viviparous, or ovoviviparous.
• How many larval stages do nematodes typically have in their life cycle?

  Four larval stages and the adult form.
• What happens to the cuticle during the nematode life cycle?

  It is shed while passing from one stage to the other.
• Who is the optimum host for all nematodes?

  Man (humans).
• How do nematodes localize in their host?

  They localize in the intestinal tract.
• How do nematodes excrete their eggs?

  Their eggs pass out with the feces of the host.
• What are the classifications of nematodes based on the presence or absence of chemoreceptors?

  • Phasmid nematodes: with caudal chemoreceptors
  • Aphasmid nematodes: without caudal chemoreceptors
• Name an example of a phasmid nematode.

  Wuchereria bancrofti
• What are the modes of transmission for nematodes?

  • Ingestion of embryonated eggs
  • Ingestion of infective larvae
  • Skin penetration of L3
  • Vector-borne transmission
  • Autoinfection
  • Transmission through inhalation
• Which nematodes are transmitted through ingestion of embryonated eggs?

  Ascaris, Trichuris, Enterobius
• Which nematodes are transmitted through skin penetration of L3?

  Hookworms and Strongyloides
• What is the habitat of intestinal human nematodes?

  Small and large intestine.
• List some intestinal human nematodes.

  • Ascaris lumbricoides
  • Ancylostoma duodenale
  • Trichuris trichiura
  • Enterobius vermicularis
• What are the habitats of somatic human nematodes?

  • Lymphatics
  • Skin/subcutaneous tissue
  • Mesentery
  • Conjunctiva
• What is the common name for Wuchereria bancrofti?

  Bancroft's filarial worm
• What is the mode of transmission for filariasis?

  By the bite of blood-sucking insects (vectors are mosquitoes).
• What is the periodicity of Wuchereria bancrofti?

  Nocturnal periodicity (largest number of microfilariae occur at night).
• What is the periodicity of Loa loa?

  Diurnal periodicity (largest number during the day).
• What is the periodicity of Onchocerca volvulus?

  Nonperiodic (microfilariae circulate at constant levels).
• What is the periodicity of Brugia malayi?

  Subperiodic (higher numbers in late afternoon or at night).
• What are the habitats of filarial worms?

  • Lymphatic filariasis
  • Subcutaneous filariasis
  • Serous cavity filariasis
• What are the effects of Wuchereria bancrofti and Brugia malayi infections?

  They cause lymph edema, lymphangitis, and elephantiasis in chronic cases.
• What is the definitive host for Wuchereria bancrofti?

  Man (humans).
• What is the diagnostic stage for Wuchereria bancrofti?

  Microfilariae in the blood.
• What is the area affected by Wuchereria bancrofti?

  Lower lymphatics.
• What is the area affected by Brugia malayi?

  Upper lymphatics.
• What is the aquatic habitat for Bancroftian filariasis vectors?

  Axils of abaca and banana plants.
• What is the life cycle of Wuchereria bancrofti?

  Definitive host is man; intermediate host is female mosquitoes.