Hookworm

• Hookworms


  • Ancylostoma duodenale
  • Necator americanus
  • Strongyloides stercoralis
  • Enterobius vermicularis
  • Trichinella spiralis

  
• Hookworms


  • Soil transmitted
  • Larval lung migration
  • No autoinfection

  
• Soil transmitted

  • Ingestion of embryonated ovum (Ascaris lumbricoides, Trichuris trichiura)
  • Skin penetration (Hookworms)
  • Ingestion of encysted larva in raw fish meat (Capillaria philippinensis)

  
• Larval lung migration

  People with ascariasis will have pulmonary symptoms
• Autoinfection

  Capillaria philippinensis can undergo autoinfection
• Hookworms

  • Two species that can parasitize humans: Ancylostoma duodenale (Old World hookworm) and Necator americanus (New World hookworm)

  
• Adult hookworms

  • Small grayish-white
  • Anterior end with conspicuous bend or hook-like appearance
  • Both male and female have curved posterior ends
  • Adult female is larger than male
  • Male has expansion called caudal bursa or copulation used to hold females during copulation

  
• Ancylostoma duodenale

  Head is continuous to the same direction as the body
• Necator americanus

  Head is curved opposite to the curvature of the body
• Buccal capsule

  • Ancylostoma duodenale has 2 pairs of curved teeth
  • Necator americanus has a pair of semilunar cutting plates

  
• Spicule

  • Ancylostoma duodenale has two spicules
  • Necator americanus has a fused spicule
• Dorsal ray

  • Ancylostoma duodenale has a tridigitate dorsal ray
  • Necator americanus has a bifid dorsal ray
• Hookworm eggs

  Thin shell, cleaved embryo with 2-8 cells (can reach 16), clear space between embryo and shell, 60x40um oval shape

  
• Hookworms, Ascaris, and Trichuris are referred to as the "Holy Trinity" as they can be found in the stool of a single patient
• Pathogenesis and clinical manifestations of hookworm infection

  1. Skin at entry of filariform larva

  2. Lungs during larval migration

  3. Small intestine where adult worms reside

  
• Patients with hookworm infection will have pulmonary symptoms due to larval lung migration

  
• Hookworm

  • Thin hyaline shell
  • Embryonic cleavage

  
• Hookworms referred to as the "Holy trinity"

  • Hookworms
  • Ascaris
  • Trichuris

  
• Hookworms, Ascaris and Trichuris can be found in the stool sample of a single patient because all of them are soil-transmitted

  
• Pathogenesis and Clinical Manifestations

  1. Skin at the entry of the filariform larva

  2. Lung during the larval migration

  3. Small intestine

  
• Skin at the entry of the filariform larva

  • Ground itch or dew itch
  • Itchy and erythematous maculopapular rash
  • Marked inflammation

  
• Lung during the larval migration

  • Loeffler's syndrome
  • Dry cough, wheeze, dyspnea and fever
  • Eosinophilic pneumonia
• Small Intestine

  • Buccal capsule attaches worm to intestinal wall
  • Saliva contains anticoagulant which keeps the area bleeding
  • Abdominal pain, diarrhea and steatorrhea
  • Hookworm feed on blood of humans
  • Loss of albumin - hypoalbuminemia
  • Loss of iron in hemoglobin - microcytic hypochromic type of anemia

  
• Hookworm disease

  Ancylostomiasis; Necatoriasis

  
• Hookworm disease manifestations


  • Ground itch
  • Bronchitis and pneumonitis - Loeffler's syndrome
  • Abdominal pain, steatorrhea, diarrhea
  • Eosinophilia
  • Chronic infection: microcytic hypochromic anemia of iron deficiency type, hypoalbuminemia

  
• Diagnosis

  1. Direct Fecal Smear - demonstration of the egg in stool sample

  2. Harada-Mori Culture
• Harada-Mori Culture

  Stool sample placed in filter papers immersed in water, hookworm eggs hatch into rhabditiform larvae which eventually form filariform larvae that can be sampled from the water

  
• Treatment

  • Albendazole - drug of choice
  • Mebendazole - alternative drug
  • Anemia - iron supplementation
  • Hypoalbuminemia - adequate diet
• Prevention

  • Wear slippers or shoes to avoid skin contact with soil
  • Proper human waste disposal
  • Deworming activities
• Ancylostoma duodenale can be transmitted through ingestion of larvae and transmammary route

  
• Filariform larvae of A. duodenale can stick to vegetables, so eating raw vegetables with filariform larvae can also cause infection
• In skin penetration, ingestion of filariform larva, and transmammary route, the infective stage will still be the filariform larva

  
• Hookworm life cycle

  1. Eggs passed in stool

  2. Larvae hatch and grow in feces/soil

  3. Filariform larvae penetrate skin

  4. Larvae carried to lungs

  5. Larvae ascend to pharynx and are swallowed

  6. Larvae mature into adults in small intestine

  7. Adults attach to intestinal wall and feed on blood

  
• Hookworm summary

  • Diagnostic stage: Ova/egg in stool
  • Infective stage: filariform larva/ third stage larva/ L3 larva
  • Mode of transmission: Skin penetration
  • Autoinfection: no
  • Larval lung migration: Yes