Hook worm
- 1. Hookworm Durga Satheesh
- 2. HISTORY AND DISTRIBUTION • ancient times-ebers papyrus • tropics and subtropics • Ancylostoma duodenale and Necator americanus are human parasites. • A.duodenale described by Dubini in 1843 in Italy. Life cycle described by Looss 1898 in Egypt • N.americanus identified by Stiles 1902 in USA • A.duodenale was distributed to north and N.americanus to the south in endemic zones • Ancylostoma was prevalent along Mediterranean coast of Europe and Africa,North India,China,Japan • Necator was prevalent in central and South America Central and south Africa, South India • Now it has a blurred geographical distribution
- 3. ANCYLOSTOMA DUODENALE MORPHOLOGY o Stout, Cylindroidal o Pale pink or greyish white but appear reddish brown due to ingested blood o Body is curved, dorsal concave, ventral convex o Ant. end is constricted and bent dorsally o Mouth is directed dorsally
- 4. A prominent buccal capsule, reinforced with chitin like substance – carries two pairs of hook like teeth ventrally, dental plate with a median cleft dorsally
- 5. o Male worm 8-11mm long, 0.4mm thick o Posterior end of male is expanded into a copulatory bursa supported by fleshy rays o Rays help in differentiating between species o rectum and genital canal open into Cloaca in the bursa o 2 long retractile bristle like copulatory spicules, tips of which project from the bursa
- 6. o Female worm Larger, 10-13mm long, 0.6mm thick, hind end conoid, subterminal anus situated ventrally o Vulva opens ventrally, at the junction of middle and posterior thirds of the body o Vagina leads to 2 intricately coiled ovarian tubes o During copulation, copulatory bursa attaches to the vulva Y shaped appearance
- 9. o Eggs are oval or elliptical, 60 x 40 µm, colourless, not bile stained, with a thin transparent hyaline shell membrane o Egg contains unsegmented ovum o During its passage down intestine, ovum develops o contain 4-8 blastomeres when passed in faeces o Clear space between segmented ovum & egg shell.eggs float in sat. NaCl o 25,000-30,000 eggs a day and 18-54 million during its life time
- 11. LIFE CYCLE o Humans are the only natural host o Adult worm lives in small intestine of infected persons- jejunum o Eggs passed in faeces-not infective o Embryo develops inside eggs when deposited in soil o In about 2 days, Rhabditiform larva hatches out, 250µm long o Grows in size by feeding bacteria and organic matter and it moults twice on 3rd and 5th days after hatching o Third stage- filariform larva- infective form o 500-600µm long with a sharp pointed tail, it is non feeding form o Live in soil for 5 weeks –heads waving in air
- 12. o When a person walks barefooted, they penetrate the skin-enter subcutaneous tissue o Skin b/w toes, dorsum of foot, medial aspect of sole are common sites of entry o In subcutaneous tissue larvae enter the venules and reaches right heart and lungs o Break out of capillaries to reach alveoli- migrate up the respiratory tract to the epiglottis o They crawl over epiglottis to pharynx and are swallowed
- 13. o In jejunum, they moult and develop a temporary buccal capsule-get attaches to gut o Feed and grow in size, undergo 4th and final moulting, develop buccal capsule and grow into adults o From time of infection, it takes 6 wks for the worm to become sexually mature o Rarely infection occurs through buccal route o Transmammary and transplacental transmission has been reported
- 14. LIFE CYCLE OF ANCYLOSTOMA
- 15. NECATOR AMERICANUS MORPHOLOGY o Adult worms are slightly smaller than A.duodenale o Male 7-9 mm long and 0.3mm thick o Female 9-11mm long and 0.4mm thick o Anterior end is bent in the opposite direction of general curvature of body o They have a smaller buccal capsule with two pairs of semilunar cutting plates
- 17. o Copulatory bursa is long and wide o Copulatory spicules are fused at the ends to form a barbed tip o In the female vulva is placed in the middle of the body o Eggs are identical with those of A.duodenale o Life cycle is also similar. Life span is much longer about 4-20 yrs o 2-7 yrs in A duodenale
- 18. necator
- 19. DISTINGUISHING FEATURES B/W ANCYLOSTOMA AND NECATOR ANCYLOSTOMA NECATOR ADULT ANTERIOR CURVATURE ANTERIOR CURVATURE IN UNIFORM WITH BODY OPPOSITE DIRECTION FEMALE CURVE VULVA OPENS AT JUNCTION OF OPENS A LITTLE IN FRONT OF THE MIDDLE AND POSTERIOR MIDDLE THIRD BUCCAL 2 PAIRS OF HOOK LIKE 2 PAIRS OF SEMILUNAR CUTTING TEETH VENTRALLY AND A PLATES INSTEAD OF TEETH CAPSULE DENTAL PLATE WITH MEDIAN CLEFT DORSALLY COPULATOR THE DORSAL RAY IS SINGLE HAS A PAIRED DORSAL RAY WITH A SPLIT END Y BURSA COPULATOR SEPERATE FUSED AT TIP Y SPICULES
- 20. PATHOGENESIS AND CLINICAL FEATURES o When filariform larva enters the skin, they cause severe local itching o Erythematous papular rash may develop o Scratching and secondary bacterial infection may follow o This condition is called Ground itch, occurs when large number of larvae penetrate the skin, more common with necator o Larvae sometimes cause creeping eruption- more common in animal hookworms
- 21. • Larvae migrate between stratum germinativum & S. corneumserpi genous vesicular lesion
- 22. o When larvae enters the alveoli, they may cause minute local haemorrhages. o Clinical pneumonitis develops only in massive infections o Important manifestations of ancylostomiasis is in the intestine o Worms attach to gut mucosa by their buccal capsules o Suck a portion of intestinal villi, utilise gut epithelial cells and plasma for their food o The worm sucks in blood, which passes out undigested through its intestines o Adult ancylostome can suck about 0.2ml blood and necator sucks 0.03ml per day o The worms frequently leave one site and attaches to another site
- 23. o Bleeding from the site continue for sometime due to the anticoagulant activity of the secretions of the worm o Blood loss over a period of time leads to microcytic hypochromic iron deficiency anaemia o Degree of anaemia is directly proportional to worm burden o Worm loads upto 100 worms cause no symptoms,500-1000 or more cause significant blood loss and anaemia o Egg count less than 5 eggs per mg of faeces cause no clinical disease,20 eggs or more significant anaemia, 50 or more massive infection
- 24. o In hookworm disease, intestinal absorption of iron is normal so oral administration of iron can correct anemia o Hookworm infection cause intestinal syndrome resembling peptic ulcer- with epigastric pain, dyspepsia and vomiting. o Reddish or black stool, diarrhoea may be seen in acute stage o Anaemia leads to lassitude and dullness, hypoprotenemia etc o Severe hookworm anemia leads to cardiac failure
- 25. DIAGNOSIS o Demonstration of eggs in faeces by direct microscopy or by concentration methods o Rhabditiform larvae may present in samples which are examined 24 hrs or more after collection TREATMENT o MEBENDAZOLE o PYRANTEL PAMOATE o THIABENDAZOLE is less effective o BEPHENIUM HYDROXYNAPHTHOATE is active against Ancylostoma but not against Necator
- 26. EPIDEMIOLOGY AND PREVENTION o Conditions required for maintenance of endemic hookworm infection are 2. Presence of infected persons 3. Dispersal of eggs in soil 4. Appropriate environmental factors facilitating development of eggs 5. Opportunity for the larvae to infect people through exposed skin surface o These conditions prevail throughout the year-in tropics but in subtropics it exist only seasonally-in warmer months o Prevention of SOIL POLLUTION WITH FAECES,USE OF FOOTWEAR,GLOVES,TREATMENT OF PATIENTS AND CARRIERS etc can limit the infection
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