Hookworm

Hookworm is one of the most important small intestinal nematodes causing iron deficiency anemia. This PPT illustrates hookworms associated with human diseases, life cycle, pathogenesis, laboratory diagnosis, treatment and prevention of hookworm infection.

1. HOOKWORM Ms Mary Mwinga

2. 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 Spp: Ancylostoma duodenale Necator americanus

3. 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

4. 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

5. MORPHOLOGY Adult worm and egg Adult Worm: small, greyish white and cylindrical Anterior end- bent dorsally = hence name hookworm Oral aperture- directed towards dorsal surface Buccal capsule- has 6 teeth, 4 hook-like on the ventral surface and 2 knob-like on the dorsal surface. Male worm differs from female worm

6. Differences between Adult male and female A. duodenale Characteristic Male Female Size Smaller- 5 to 11 mm long x 0.4 mm wide larger /longer than male 9 to 13 mm long x 0.6 mm wide Posterior end Expanded in an umbrella like fashion Named as copulatory bursa Tapering and no expanded bursa Genital opening Posterior and opens with cloacae Present at junction of posterior and middle third of body

7. Copulatory bursa Present in male For attachment with female during copulation Consists of 3 lobes, one dorsal and two lateral lobes Each lobe: supported by chitinous rays= 13 3 at dorsal lobe and 10 at the two lateral lobes Dorsal ray is partially divided at tip Each division is tripartite Life span adult worm in human intestine: 3 to 4 years

8. EGG Oval shaped Size: 65 µm long x 40 µm wide Colourless- non-bile stained Surrounded by a thin transparent hyaline shell-membrane Contains a segmented ovum with four (4) blastomeres Clear space between egg shell and segmented ovum. 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

9. 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)

10. In soil : rhabditiform larva hatches from each egg (24-48 hours) size: 250 µm x 17 µm. moults twice on 3 rd and 5 th 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

11. 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 3 rd moulting

12. Settles in small intestines undergo 4 th 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

13. 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

14. 1. 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

15. 2. 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.

16. Human- infected by walking barefoot  contacting moist soil contaminated with animal faeces Creeping eruptions may occur occasionally by A. duodenale and N. americanus.

17. 3. 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

18. 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 sometime These leads to iron deficiency anaemia of microcytic, hypochromic type

19. 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.

20. 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)

21. 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.

22. Indirect methods Blood examination: reveals microcytic, hypochromic anaemia and eosinophilia Stool exam: shows occult blood and Charcot-Leyden crystals

23. 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

24. 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

25. ADULT WORMS ANCYLOSTOMA DUODENALE NECATOR AMERICANUS Size Large and thick Small and slender Buccal capsule Large and oval Contains 2 pairs of claw like teeth on the ventral surface and 1 pair of knob like teeth on the dorsal surface Small and round Contains 1 pair of chitinous plates on ventral surface and 1 pair of plates on the dorsal surface Anterior end Bends in the same direction as the body curvature Bends in the opposite direction as the body curvature Posterior end Posterior spine present in female worm No posterior spine Copulatory bursa Dorsal ray is single and bifurcated Each bifurcation again divides into three rays 13 rays Dorsal ray split form base Each bifurcation is again divided into two 12 rays Vulva Present behind the middle of the body Present in front of the middle of the body

26. BUCCAL CAPSULE

27. COPULATORY BURSA ANCYLOSTOMA DUODENALE NECATOR AMERICANUS

28. EPIDERMIOLOGY Western world- Africa and America In India – all except in Punjab, Uttar Pradesh

29. T reatment 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

30. 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).