intestinal nematodes

• Fertilized ova


  Eggs that have been fertilized
• Monoecious


  Having both male and female reproductive organs
• Dioecious


  Having separate male and female individuals
• Cloaca


  A common opening for the digestive, urinary, and reproductive systems
• Ascaris lumbricoides


  Giant intestinal roundworm
• Human Ascariasis


  Disease caused by Ascaris lumbricoides
• Adult Ascaris lumbricoides


  • Male measures 15-30 cm x 3 mm, female measures 20-48.5 cm x 5 mm
  • Cylindrical, elongated, separating gradually at the anterior end
  • Smooth finely striated cuticle with a faint longitudinal white lateral line
  • Terminal mouth with trilobate lips and a small triangular buccal cavity
• Fertilized egg


  Broadly ovoid, golden brown in color with thick transparent shell made up of 3 layers: vitelline membrane, glycogen membrane, albuminous/mammillary coat
• Unfertilized egg


  Generally larger, longer, elongated or sometimes irregular in shape. Eggshell consists of only 2 layers: glycogen membrane and irregular coating of albuminous layer. Vitelline layer is absent.
• Life cycle of Ascaris lumbricoides


  Adult in small intestine -> Eggs pass out in feces -> Embryonation of fertilized eggs in soil in 1-2 weeks -> Fully embryonated eggs ingested by man -> Eggs hatch and larvae penetrate mucosa and enter blood circulation -> Larvae reach heart and lungs, molt twice -> Larvae ascend respiratory tree and swallowed, descend to small intestine to mature
• Pathology due to larval migration


  • Larval migration to lungs can produce pneumonitis resembling asthmatic attack with eosinophilia (Ascaris pneumonitis or Loeffler's syndrome)
  • Ectopic larva may initiate granulomatous reactions in organs like brain, spinal cord, kidneys
• Pathology due to adult worm

  • Small numbers may not show symptoms
  • Serious effects due to erratic migration - may be regurgitated, vomited, escape through nostrils, invade bile duct, gall bladder, liver, appendix, cause intestinal obstruction
  • Fever and certain drugs are causative factors of Ascaris migration
• Diagnosis


  • Finding eggs in feces by DFS, Kato-thick, Kato-Katz or Concentration technique (FECT)
  • Stool examination may give negative finding in certain conditions
• Ascaris specific antibodies


  Can be detected by Ascaris specific peptides in dot EIA
• Drugs for treatment


  • Albendazole
  • Levamisole
  • Mebendazole
  • Piperazine salts
  • Pyrantel pamoate
• Transmission


  Ingestion of contaminated food or water with embryonated egg/ova
• Toxocara canis and Toxocara cati


  Dog ascaris and Cat ascaris
• Toxocariasis or Visceral Larva Migrans (VLM)

  Disease caused by accidental infection of humans by Toxocara larvae
• Life cycle of Toxocara


  Same as Ascaris lumbricoides
• Pathology of Toxocara infection

  • Larval migration may produce hemorrhage, necrosis, granuloma, eosinophilia, liver damage, pulmonary inflammation
• Whenever infected dogs and cats are present, the eggs are threat to human, especially for children exposed to contaminated soil
• Trichuriasis


  Disease caused by Trichuris trichiura
• Adult Trichuris trichiura


  • Flesh colored or pinkish, anterior is attenuated and whip-like, posterior is more robust
  • Female is slightly larger than male, measures 3.5-5 cm in length with straight posterior end, male measures 3-4.5 cm with coiled posterior end
• Trichuris trichiura egg


  Characteristically barrel-shaped/lemon-shaped/football shaped or Japanese lantern in appearance with prominent bipolar plugs on both ends
• Life cycle of Trichuris trichiura


  Adult worm inhabits caecum, fertilized eggs passed out in feces, embryonation in soil, ingested eggs hatch and larvae penetrate intestinal wall, pass down to caecum to transform into adult
• Pathology of Trichuriasis


  • Light infection usually asymptomatic, heavy infection can cause frequent small blood-streaked diarrhoeic stool, abdominal pain, nausea, vomiting, anemia, weight loss, rectal prolapse
• Diagnosis of Trichuriasis


  Demonstration of characteristic barrel-shaped ova in stool by DFS, Kato-thick, Kato-Katz or FECT
• Drugs for treatment of Trichuriasis

  • Albendazole
  • Mebendazole
  • Pyrantel pamoate
• Necator americanus


  New World hookworm, American hookworm, American murderer
• Necatoriasis, Uncinariasis, Tropical anemia "Laziness"


  Diseases caused by Necator americanus
• Ancylostoma duodenale


  Old World hookworm
• Ancylostomiasis, Miner's anemia


  Diseases caused by Ancylostoma duodenale
• Ancylostoma braziliense


  Cat hookworm
• Cutaneous Larva Migrans, Creeping eruption


  Diseases caused by Ancylostoma braziliense and Ancylostoma caninum
• Ancylostoma caninum


  Dog hookworm
• Ancylostoma ceylanicum


  Causes intestinal infection in humans
• Adult Ancylostoma duodenale


  • Relatively stout, body contour follows general curvature resembling letter "C", large buccal capsule with 2 pairs of ventral teeth, male has funnel-like copulatory bursa
• Adult Necator americanus


  • Small, tends to go against general body curvature resembling "S" shape, buccal capsule with pair of semi-lunar cutting plates, male has longer than broad copulatory bursa
• Adult Ancylostoma braziliense


  • One of the smaller hookworm species, buccal capsule with pair of large teeth and pair of inconspicuous median teeth, bursa copulatrix almost as broad as long
• Adult Ancylostoma caninum


  • Wide buccal capsule bearing 3 pairs of ventral teeth, cephalic/amphidial gland secretes anticoagulant, male has long slender rays supporting bursa