Hookworm is a parasitic roundworm that infects the small intestine and is a major cause of iron-deficiency anemia globally. Two main species that infect humans are Ancylostoma duodenale and Necator americanus. The hookworm life cycle involves eggs passing in feces and hatching into larvae in soil which can penetrate human skin, then migrating through tissues and lungs before reaching the small intestine where they mature into adult worms that attach and feed on blood, causing anemia. Over 900 million people are estimated to be infected worldwide, especially in tropical and subtropical regions, where walking barefoot can facilitate skin penetration by larvae. Symptoms include epigastric pain, diarrhea, coughing up blood

1. Hookworm
Introduction
• Widely distributed in tropical and sub tropical countries
• One of small intestine nematodes
• Important cause of Iron deficiency anaemia
• Named so – anterior end of adult worm is bent
• Belongs to family Ancylostomatidae
• 2 important human Species: Ancylostoma duodenale, Necator americanus
Ancylostoma duodenale
• Also called old world hookworm
• Causes ancylostomiasis
• Dubini in 1843 described the parasite
• Arthur Loss in 1896 described pathogenesis and mode of infection
Epidemiology
• Globally 900 million people infected. Necator- 835 million & Ancylostoma- 135 million • Hookworm
infection is prevalent in the tropics and subtropical countries – Asia, Africa, America, China and Southern
Europe
• In India – prevalent in Punjab, Uttar Pradesh and Bihar
• Males & young adults commonly affected
• Anaemia severe in children & pregnant women
Morphology
Adult worm
Adult Worm:
• Life span adult worm in human intestine: 3 to 4 years
Egg
• Egg floats in saturated salt solution
• Single female worm- lays about 25 000 to 30 000 eggs/day
• Eggs are excreted in faeces 4-7 weeks after infection
Life cycle of Hookworm
• Definite host: man
In small intestines: Adult worm inhabit small intestine of man
• Attachment to mucous membrane by help of mouth parts
• Eggs contain segmented ova with 4 blastomeres- passed out in faces of infected person (non-infective)
In soil: rhabditiform larva hatches from each egg (24- 48 hours)
• size: 250 µm x 17 µm.

2. • moults twice on 3rd and 5th day
• develops into filariform larva.
→ size: 500-700 µm long
→ is the infective form- penetrates unbroken skin (of toes, dorsum of foot and medial aspect of sole)
→ Remains infective up to 6 weeks
People at risk:
• Walking barefoot on soil containing filariform larva
• Farm workers: larva penetrates skin of hands
• reaches subcutaneous tissues and enters lymphatics or small venules
• Lymph to venous circulation into right heart
• into pulmonary capillaries- break through and enters alveolar spaces
• migrates to bronchi, trachea and larynx- crawl over the epiglottis to pharynx → gets swallowed
• During migration through oesophagus → undergo 3rd moulting
• Settles in small intestines → undergo 4th moulting and develop into adult worms.
• Attach to small intestine by their mouth parts
• After 6 weeks- mature sexually
• Fertilization occurs
• Female begin to lay eggs in faeces → cycle repeats
Pathogenesis and clinical manifestations
• Infective form: filariform larva
• Portal of entry- skin
• Worm causes hookworm disease- characterized by anaemia.
• Effects are due to –migrating larva or adult worm
• Migrating larva lesions:
→ Ancylostoma dermatitis or ground itch
→ Creeping eruption or cutaneous larva migrans
→ Lesions in lungs
Ancylostoma dermatitis/ground itch
• Occurs at site of entry
• Entry of filariform in skin cause dermatitis
• Leads to intense itching and burning
• Followed by erythema and oedema of the area
• Develop into papular and vesicular eruptions
• Disappears within 1 to 2 weeks.
• Common in N. americanus
Creeping eruption/cutaneous larva migrans
• Condition where filariform larva wander about the skin
- producing reddish itchy papule along path traversed by the worm Seen mostly in animal (cats, dogs
and others)
- Animal filariform cannot penetrate below level of stratum germinativum and stratum corneum
Animal agents:
- Ancylostoma braziliense (dogs and cats)
- A. caninum (dog hookworm)
- Uncinaria stenocephalia (dog hookworm)
- Bunostomum phlebotomum (cattle hookworm)
- Gnathostoma sp.

3. • Human- infected by walking barefoot → contacting moist soil contaminated with animal faeces
• Creeping eruptions may occur occasionally by A. duodenale and N. americanus.
Lesions in the lungs
• Bronchitis and bronchopneumonia
• Marked eosinophilia occurs
• Caused by adult worm
• Disease= hookworm disease
• Features:- microcytic hypochromic anaemia
• Hookworm ingest blood
• Other features: cough, dyspnoea
Intestinal manifestations
• Attach to mucosa of small intestines
• Adult worm of A. duodenale sucks more blood (0.2 ml/day) than for N. americanus.
• Worm migrate to another site leaving small bleeding points
• Worm secretions possess anticoagulant activity → bleeding from sites continue for sometimes.
• These leads to iron deficiency anaemia of microcytic, hypochromic type
• Degree of anaemia depends on: number of worms, body iron store, dietary iron
• Development of low grade fever, epigastric pain, dyspepsia, vomiting and diarrhoea.
• Stool: reddish to black
• Symptoms and signs of anaemia present.
Laboratory Diagnosis
Direct Methods:
• Stool examination: to find the adult worm or characteristic hookworm eggs
• Stool concentration: required to detect light infections
• Larva- seen if stool is kept at room temperature after 24 hours (not preserved)
• May resemble Strongyloides larvae
•Adult female hookworm- produce 2500 to 5000 eggs/day.
- Stool egg count: indicates number of adult hookworms present
• Indicates severity of infection
- Duodenal contents- reveals eggs or adult worms.
Indirect methods:
• Blood examination: reveals microcytic, hypochromic anaemia and eosinophilia
• Stool exam: shows occult blood and Charcot-Leyden crystals
Stool culture:
• Eggs hatch out and develop into filariform larva (L3) stage
• Takes place in 5-7 days
Culture techniques used:
• Harada Mori filter paper tube method
• Petridish (slant culture) technique - Baermann funnel technique - Charcoal culture method - Agar plate
technique (more sensitive) Other findings: hypochromic microcytic anaemia Chest x-ray- show patchy
infiltration of lungs
Necator americanus
• Has similar life cycle, pathogenesis and lab diagnosis like for A. duodenale.
• Adult worm- slightly smaller than Ancylostoma
• Eggs of Ancylostoma and Necator are similar and hence can be differentiated by morphological study of
adult worms and larvae

4. Epidemiology
• Western world- Africa and America
• In India – all except in Punjab, Uttar Pradesh
Treatment
• Mebendazole- 100 mg twice daily for 3 days
• Albendazole- 400 mg single dose
• Pyrantal pamoate – 11 mg/kg for 3 days
• Mild iron-deficiency anaemia- oral iron
• Severe infections with protein loss and malabsorption: nutritional support and oral or parenteral iron
replacement
Prevention
• Personal care:
- improved personal hygiene
- proper disposal of faeces
- improved nutrition with dietary iron
- treatment of infected persons
• Prophylaxis: experimental animal vaccines: using larval or adult stage antigen.
• Human trials: targeting Ancylostoma secreted proteins (ASP).