NAMETODES

• Adult worms


  Cylindrical, elongated, mostly bilaterally symmetrical, non-segmented

  
• Adult worms


  • Have specialized anterior structures capable of causing abrasion, facilitating attachment, and initiating sensory responses. These structures may include lips, plates, hooks, papillae, teeth

  
• Digestive system of adult worms

  1. Mouth at anterior end

  2. Buccal cavity - tubular/funnel-shaped

  3. Esophagus - muscular tube that pumps food posteriorly into intestines (filariform, rhabditiform, spirurpoid, strongyform, stichosoma)

  4. Intestine/midgut - flattened tube with wide lumen

  5. Rectum - short, lined with cuticle (female), joined with genital duct (forms cloaca; male)

  
• Nervous system


  • Consists of a dorsal, ventral, and four longitudinal trunks with transverse commissures
• Excretory system


  • Consists of two lateral canals that lie in the lateral longitudinal cords of hypodermis
• Reproductive system


  • Male reproductive organs situated in posterior third of body as single coiled or convoluted tube (testis, vas deferens, seminal vesicle, ejaculatory duct)
  • Females produce 20 to 200,000 eggs per day, egg consists of multinucleated mass or protoplasm usually containing yolk granules

  
• Adult worms


  • Non-hermaphroditic, males are smaller with curved posterior ends, females are larger with pointed posterior ends

  
• Locations of adult intestinal nematodes

  • Small intestine (Ascaris, Strongyloides, Hookworm, Capillaria, T. spiralis adult)
  • Large intestine (Enterobius, Trichuris)
  • Extra intestinal (T. spiralis larva, Filarial worms, D. medinensis, A. cantonensis)

  
• Life cycle of parasitic nematodes

  1. 4 larval stages

  2. Adult stage

  3. Growth and molt of cuticle (ecdysis) between stages

  4. Ingestion of contaminated food/water

  5. Skin penetration of infective larval stage

  6. Bite of infected arthropod

  7. Inhalation of infective stage

  8. Duration 1-12 months, some survive 14+ years

  
• Factors contributing to nematode infections

  • Warm, tropical climate
  • Poor sanitation and personal hygiene
  • Crowded conditions (e.g. day care)
  • Immunocompromised individuals (e.g. malnutrition)
  • Eating undercooked meat or dirt/clay
• Pathogenesis and clinical symptoms

  • Passage of worm by mouth, rectum, etc.
  • Skin ulcers
  • Abdominal cramps, loss of appetite, diarrhea, constipation, flatulence, weight loss
  • Nausea, vomiting, fever
  • Skin irritation, skin blisters, eosinophilia, anemia

  
• Lab diagnosis


  • Recovery of eggs, larvae, and adult worms
  • Specimens: stool, tissue biopsy, skin ulcers, blood, cellophane tape
  • Tests: Direct fecal smear, microscopy, serologic tests
• Ascaris lumbricoides


  Also known as: Large/Giant intestinal roundworm, Roundworm of Man, Lumbricus teres, Eenworm

  
• Ascariasis


  Roundworm infection

  
• Ascaris lumbricoides life cycle

  1. Infective stage: Embryonated egg

  2. Heart-lung migration

  3. Multiply and produce up to 250,000 eggs/day

  4. Viable in soil, fecal matter, sewage, water for years

  5. Eggs not easily destroyed by chemicals, may survive 10% formalin

  
• Ascaris lumbricoides lab tests

  • DFS
  • Kato-thick
  • Kato-katz
  • Concentration techniques
  • Serologic tests
• Ascaris lumbricoides pathogenesis and clinical symptoms

  • Asymptomatic
  • May cause tissue damage and secondary bacterial infection
  • Usual symptoms: Abdominal pain, Vomiting, Fever, Distention, Discomfort due to exit of adult worms
  • Pulmonary symptoms: Low-grade fever, Cough, Eosinophilia, Pneumonia
  • Asthmatic reaction and death may also occur

  
• Ascaris lumbricoides treatment


  • Albendazole
  • Mebendazole
  • Pyrantel pamoate
• Trichuris trichiura


  Also known as: Whipworm
• Trichuriasis


  Whipworm infection
• Trichuris trichiura life cycle

  1. Infective stage: Embryonated eggs

  2. Female worms may lay 3,000 to 10,000 eggs/day

  3. Eggs: 1 month development outside human body to become infective

  4. Adult worms may live 4-8 years if untreated

  
• Trichuris trichiura lab tests

  • DFS
  • Kato-thick
  • Kato-katz
  • Concentration techniques
  • Zinc sulfate flotation method
• Trichuris trichiasis pathogenesis and clinical symptoms

  • Asymptomatic
  • Enterorrhagia is common
  • Appendicitis or granuloma formation: Lumen of appendix filled with worms
  • Trichuris dysentery syndrome: Chronic dysentery + Rectal prolapse
  • Blood-streaked diarrheal stool, abdominal pain, tenderness, nausea, anemia, vomiting, weight loss
• Trichuris trichiura treatment


  • Albendazole
  • Mebendazole
• Enterobius vermicularis


  Also known as: Pinworm, Seatworm, Social/Society worm, Oxyuris vermicularis

  
• Enterobiasis


  Pinworm infection

  
• Enterobius vermicularis life cycle

  1. Infective stage: Embryonated egg

  2. Gravid female usually lays up to 15,000 eggs/day

  3. After egg deposition, the female usually dies

  
• Enterobius vermicularis lab tests

  • DFS
  • Cellophane tape preparation
• Enterobius vermicularis pathogenesis and clinical symptoms

  • Asymptomatic
  • Intense itching and inflammation of anal or vaginal area
  • Intestinal irritation, mild nausea, vomiting, irritability, difficulty sleeping
  • Mild intestinal inflammation and abdominal pain
  • Complications: appendicitis, vaginitis, endometritis, salpingitis, peritonitis
• Enterobius vermicularis treatment


  • Albendazole
  • Mebendazole
  • Pyrantel pamoate
• Hookworms


  Necator americanus - "New World Hookworm", Ancylostoma duodenale - "Old World Hookworm"

  
• Hookworm infection


  Ancylostomiasis, Necatoriasis, Iron Deficiency Anemia (IDA), Wakana's disease

  
• Hookworm life cycle


  1. Infective stage: Filariform larva

  2. Heart-lung migration

  3. Adult females lay 10,000 to 20,000 eggs/day

  
• Hookworm lab tests


  • DFS
  • Serodiagnosis technology
  • Kato thick or Kato-Katz method
  • Concentration techniques
  • Harada-Mori
  • PCR
  • ELISA

  
• Hookworm pathogenesis and clinical symptoms

  • Asymptomatic
  • Ground/dew itch, blood sputum, wheezing, headache, mild pneumonia with cough, gastrointestinal symptoms, slight anemia, weight loss or weakness, diarrhea, anorexia, edema, pain, enteritis, epigastric discomfort
  • Hypoalbuminemia

  
• Hookworm treatment


  • Albendazole
  • Mebendazole
  • Pyrantel pamoate
  • Iron replacement and other dietary therapy (asymptomatic)
  • Thiabendazole (cutaneous larva migrans)

  
• Strongyloides stercoralis


  Also known as: Threadworm, Military worm

  
• Strongyloidiasis


  Threadworm infection

  
• Strongyloides stercoralis life cycle

  1. Infective stage: Filariform larva

  2. Heart-lung migration

  3. Parthenogenic - form of asexual reproduction by self-impregnation

  
• Strongyloides stercoralis lab tests

  • DFS
  • Concentration techniques
  • Harada-mori
  • Enterotest
  • ELISA