Lesson 2_Phylum Nematoda Part 1

• Nematodes


  Intestinal (small and large intestine) and Extraintestinal Nematodes
• Mnemonics for small and large intestinal parasities

  • CASH (small)
  • TE (Large)
• Nematodes


  • Most worm-like of all helminths
  • Slender and unsegmented compared to earthworms
  • Considered as the prototype of worms
  • Elongated, cylindrical, unsegmented worms with tapering ends
  • Nematode-means thread-like, from nema meaning 'thread'
  • They have separate sexes; can be classified as male and female
  • Bilaterally symmetrical
  • Can be classified into three classifications: Ova/Egg, Larval Stages – L1, L2, L3, L4, Adult Form

  
• Life cycle of nematodes


  1. Ova are deposited in the environment and are developed into larval 3

  2. Once the parasite reach L3, the parasite can enter the host and can be an adult parasite (female or male)

  3. The ova produced by the female can go back to the environment

  
• Ascaris lumbricoides


  • Common names: Large intestinal roundworm, roundworm of man
  • Causes: Ascariasis, roundworm infection
  • A soil-transmitted helminth
  • Ascariasis - considered as the most common intestinal helminth infection in the world

  
• Ascaris lumbricoides (unfertilized egg)

  • Size: 85-95 um by 38-45 um
  • Shape: Varies
  • Embryo: Unembryonated Amorphous mass (Lecithin) of protoplasm
  • Shell: Thin
  • Other: Usually Corticated (with ridges)

  
• Ascaris lumbricoides (fertilized egg)

  • Size: 40 – 75 um by 30 – 50 um
  • Shape: Rounder than nonfertilized version
  • Embryo: Undeveloped unicellular embryo
  • Shell: Thick Chitin
  • Other Features: May be corticated or decorticated

  
• Ascaris lumbricoides (adult)


  • Females are larger than males
  • The infective stages of nematodes are L3

  
• Usual infection of 10-20 Ascaris worms may not show symptoms

  
• Ascaris pneumonitis (Loeffler's Syndrome)


  Chest pain, cough, fever, increased eosinophil (with heart to lung migration)
• Eosinophil are disrupted by the parasites and go into the bloodstream which is why it is increased
• Lung infiltration, asthmatic attacks and edema of the lips
• Difficulty in breathing
• Treatment for Ascariasis


  Albendazole and Mebendazole
• Mnemonics of heart lung migration


  • A - Ascaris Lumbricoides
  • S
  • H
• Trichuris trichiura

  • Common name: Whipworm
  • Causes: Trichuriasis or whipworm infection
• Trichuris trichiura (egg)


  • Size: 50 – 55 by 25 um
  • Shape: Barrel, football; hyaline polar plug at each end
  • Embryo: Unicellular; undeveloped
  • Shell: Smooth; yellow – brown color because of bile contact

  
• Trichuris trichiura (adult)

  • Size: 2.5 cm long; males usually smaller than females
  • Anterior End: Colorless; resembles a whip handle; contains a slender esophagus
  • Posterior End: Pinkish – gray; resembles whip itself; contains digestive and reproductive systems; males possess prominent curled tail
• Trichuris trichiura is the 3rd most common helminth; found primarily in warm climates
• Poor sanitation practices
• Symptoms of Trichuriasis in children

  Ulcerative colitis, chronic dysentery, severe anemia and possibly growth retardation
• Symptoms of Trichuriasis in adults

  Inflammatory bowel disease, weight loss, weakness and mucoid or bloody diarrhea
• Hookworm

  • The term hookworm refers to two organisms: Necator Americanus and Ancylostoma Duodenale
  • Soil transmitted helminths
  • Blood sucking nematodes that attach to the mucosa of the small intestine

  
• Ancylostoma duodenale (hookworm egg)

  • Length: 55-60 um
  • Width: 35 – 40 um
  • Shell: Colorless
  • 8 blastomere

  
• Necator americanus (hookworm egg)

  • Length: 60 – 75 um
  • Width: 35 – 50 um
  • Shell: Colorless
  • 4 – 6 blastomere

  
• Hookworm larvae

  • L1 and L2
  • L3 and L4 (infective and invasive)

  
• Hookworm infection is usually chronic, hence patients show no acute symptoms
• Symptoms of hookworm infection

  • Patients who are repeatedly infected may develop intense allergic itching at the site of hookworm penetration (ground itch - cutaneuous larva migrans)
  • May develop a microcytic hypochromic iron deficiency, weakness, and hypoproteinemia