Introduction to Nematodes and Nematodes 1 & 2

• What is the phylum of nematodes?

  Nemathelminthes (Nematoda)
• Why are nematodes considered worm-like?

  They resemble the common earthworm appearance
• What does the name "nematode" mean?

  Thread
• Where are free-living nematodes typically found?

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

  Elongated and cylindrical
• What are the sensory organs of nematodes?

  Amphids and phasmids
• What is the function of amphids in nematodes?

  Serve as chemoreceptors
• How do nematodes move?

  By contraction of longitudinal muscles
• What covers the body wall of nematodes?

  A tough outer cuticle
• What are the sexes of nematodes?

  Diecious (separate sexes)
• What is parthenogenesis in nematodes?

  Females fertilize their own eggs
• How does the size of male nematodes compare to females?

  Males are generally smaller
• What are the reproductive methods of female nematodes?

  Oviparous, viviparous, or ovoviviparous
• How many larval stages do nematodes typically have?

  Four larval stages
• What happens to the cuticle during the nematode life cycle?

  It is shed between stages
• Who is the optimum host for nematodes?

  Humans
• Where do nematodes localize in their host?

  In the intestinal tract
• How do nematode eggs exit the host?

  With the feces of the host
• What are the most commonly encountered nematodes in the laboratory?

  Intestinal in nature
• What are the classifications of nematodes based on chemoreceptors?

  • Phasmid nematode: with caudal chemoreceptors
  • Aphasmid nematode: without caudal chemoreceptors
• What is an example of an aphasmid nematode?

  Trichuris trichiura
• What are the modes of transmission for nematodes?

  1. Ingestion of embryonated eggs
  2. Ingestion of infective larvae
  3. Skin penetration of L3
  4. Vector-borne transmission
  5. Autoinfection
  6. Transmission through inhalation
• What are the habitats of intestinal and somatic human nematodes?

  Intestinal Human Nematodes:

  • Small intestine: Ascaris, Ancylostoma, etc.
  • Large intestine: Trichuris, Enterobius, etc.

  
  

  Somatic Human Nematodes:

  • Lymphatics: Wuchereria, Brugia
  • Skin/subcutaneous tissue: Loa, Onchocerca
• What is the common name for Wuchereria bancrofti?

  Bancroft's filarial worm
• What is the infective stage of filarial worms?

  Microfilariae
• What is the mode of transmission for filarial worms?

  By the bite of blood-sucking insects
• What is nocturnal periodicity in filarial worms?

  Microfilariae appear in blood at night
• What is diurnal periodicity in filarial worms?

  Microfilariae appear in blood during the day
• What is nonperiodic microfilariae?

  Microfilariae circulate at constant levels
• What is the habitat of filarial worms?

  In lymphatic vessels and blood
• What is the definitive host for Wuchereria bancrofti?

  Man
• What is the life cycle of Brugia malayi compared to Wuchereria bancrofti?

  Similar but prefers upper lymphatics
• What causes classical filariasis?

  Blockage of lymph vessels by adult worms
• What is acute filarial disease characterized by?

  High-grade fever and lymphatic inflammation
• What is lymphedema?

  Swelling due to lymphatic blockage
• What are the stages of chronic filarial disease?

  1. Swelling around the ankle
  2. Spreading to the foot and leg
  3. Affects arms, breast, scrotum, etc.
  4. Edema becomes hard and non-pitting
• What is the definition of itis?

  Inflammation of lymph nodes
• Which lymph nodes are most commonly affected?

  Inguinal nodes
• What conditions frequently involve the lymphatics of the testes?

  Epididymo-orchitis and funiculitis
• What is more commonly encountered, chronic or acute filarial disease?

  Chronic filarial disease