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INTESTINAL NEMATODES

INTESTINAL NEMATODES. Strongyloides stercoralis. Adult worms. 2 - 2.5mm, ovoviviparous, eggs laid in the tissues. Free living worms. Moist soil. Infective form. Filariform larvae. Mode of transmission. Penetration / autoinfection. Site of localization.

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INTESTINAL NEMATODES

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  1. INTESTINAL NEMATODES

  2. Strongyloides stercoralis Adult worms 2 - 2.5mm, ovoviviparous, eggs laid in the tissues Free living worms Moist soil Infective form Filariform larvae Mode of transmission Penetration / autoinfection Site of localization Wall of Small intestine, mainly duodenum & jejunum

  3. Life cycle – S. stercoralis Larvae reach intestine Adult worms in intestine Eggs in intestine Rhabditiform larvae hatch Larvae pass through similar to Ascaris Autoinfection Larvae in feces - soil Rhabditiform to filariform Direct Indirect Larvae in blood Larvae into adults Larvae penetrate intestine Eggs produced Penetrate skin Filariform larvae (infective form) Rhabditiform larvae hatch

  4. Pathogenicity • Skin lesions (2 types) – “larva currens” • At the site of entry – urticarial rash • In the perianal region – linear, erythematous urticarial wheal • Pulmonary lesions – due to migrating larva • Alveolar hemorrhages • Bronchopneumonia • Intestinal lesions - “burrowing lesions” • Epigastric pain • Diarrhoea with blood & mucus • Nausea • Weight loss

  5. Important terms to know • Autoinfection – filariform larva • In the Intestinal lumen • Perineal & perianal skin penetration • Hyperinfection – can result in autoinfection • Steroids or Immunosuppressive therapy • Malignancy • Malnutrition • Pregnancy • Puerperium • AIDS • Persistence of infection – due to autoinfection

  6. Laboratory Diagnosis • Stool examination – rhabditiform larva • Culture – larva • ELISA – to detect Abs

  7. Trichinella spiralis (Trichina Worm) Adult worms (smallest nematode infecting man) Male 1.4 – 1.6 mm Female 3 - 4 mm, viviparous Encysted larvae (100µ) in striated muscles of pig Infective form Mode of transmission Ingestion of improperly cooked pork Site of localization Small intestine Diaphragm, Intercostals, Deltoid, Pectoralis major, Biceps Commonly involved muscles

  8. Life Cycle – T spiralis Encysted larva in pig muscles (infective form) Eating under- cooked pork Larva deposit and encyst in striated muscles Larva released in small intestine 40 hrs Larva enters circulation Develop into adult worms Female deposits larva in intestinal mucosa

  9. Pathogenicity • Trichinelliasis / Trichinosis – clinical features depends on the stage: • Stage of intestinal invasion: 5-7 days, pain in abdomen, nausea, vomiting, diarrhoea • Stage of larval migration: fever, urticarial rash, splinter hemorrhages, periorbital & facial edema • Stage of encystation: asymptomatic in light infections; myalgia, weakness in heavy infections • Complications – during migration: • myocarditis, encephalitis

  10. Laboratory Diagnosis • Muscle biopsy – encysted larva • Blood – eosinophilia between 2nd & 4th week • Serology – to detect specific Abs by: • Bentonite flocculation test • Latex agglutination test

  11. Enterobius vermicularis (Pin Worm, Seatworm) Adult worms Male 2 - 5 mm, Female 8 -13 mm, oviparous 60 µ, non bile stained Plano-convex with coiled embryo Eggs Infective form Embryonated egg Mode of transmission Ingestion, Autoinfection Site of localization Large intestine – caecum & appendix

  12. Life cycle – E. vermicularis

  13. Clinical features • Due to migration of worm - Perianal, perineal & vaginal itching (pruritis) worsens at night. • Insomnia and restlessness • Nocturnal enuresis

  14. Laboratory Diagnosis • Detection of adult worms in- • Feces • Perianal region • NIH swab – scrapings from perianal region • Microscopy – non bile stained eggs

  15. Trichuris trichiura (Whip Worm) Adult worm 30 – 50 mm Eggs 60 µ, bile stained Barrel-shaped with Mucus plug at each pole Unsegmented ovum Infective form Mature embryonated eggs Mode of transmission Ingestion Site of localization Large intestine - caecum

  16. Life cycle

  17. Clinical features • Infection – Trichuriasis • Symptoms depend on worm burden • Less than 10 worms – asymptomatic • Heavier infections – • chronic profuse mucus and bloody diarrhea with abdominal pains and edematous rectum • malnutrition, weight loss and anemia

  18. Laboratory diagnosis • Stool examination – bile stained eggs with bipolar mucus plugs

  19. Key to the diagnosis of Intestinal Nematodes

  20. THANK YOU

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