Hook worm

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parasitology- ancylostoma duodenalale,necator americanus

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Hook worm

  1. 1. Hookworm Durga Satheesh
  2. 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. 3. ANCYLOSTOMA DUODENALEMORPHOLOGYo Stout, Cylindroidalo Pale pink or greyish white but appear reddish brown due to ingested bloodo Body is curved, dorsal concave, ventral convexo Ant. end is constricted and bent dorsallyo Mouth is directed dorsally
  4. 4. A prominent buccal capsule, reinforced with chitin like substance – carriestwo pairs of hook like teeth ventrally, dental plate with amedian cleft dorsally
  5. 5. o Male worm 8-11mm long, 0.4mm thicko Posterior end of male is expanded into a copulatory bursa supported by fleshy rayso Rays help in differentiating between specieso rectum and genital canal open into Cloaca in the bursao 2 long retractile bristle like copulatory spicules, tips of which project from the bursa
  6. 6. o Female worm  Larger, 10-13mm long, 0.6mm thick, hind end conoid, subterminal anus situated ventrallyo Vulva opens ventrally, at the junction of middle and posterior thirds of the bodyo Vagina leads to 2 intricately coiled ovarian tubeso During copulation, copulatory bursa attaches to the vulva Y shaped appearance
  7. 7. o Eggs are oval or elliptical, 60 x 40 µm, colourless, not bile stained, with a thin transparent hyaline shell membraneo Egg contains unsegmented ovumo During its passage down intestine, ovum developso contain 4-8 blastomeres when passed in faeceso Clear space between segmented ovum & egg shell.eggs float in sat. NaClo 25,000-30,000 eggs a day and 18-54 million during its life time
  8. 8. LIFE CYCLEo Humans are the only natural hosto Adult worm lives in small intestine of infected persons- jejunumo Eggs passed in faeces-not infectiveo Embryo develops inside eggs when deposited in soilo In about 2 days, Rhabditiform larva hatches out, 250µm longo Grows in size by feeding bacteria and organic matter and it moults twice on 3rd and 5th days after hatchingo Third stage- filariform larva- infective formo 500-600µm long with a sharp pointed tail, it is non feeding formo Live in soil for 5 weeks –heads waving in air
  9. 9. o When a person walks barefooted, they penetrate the skin-enter subcutaneous tissueo Skin b/w toes, dorsum of foot, medial aspect of sole are common sites of entryo In subcutaneous tissue larvae enter the venules and reaches right heart and lungso Break out of capillaries to reach alveoli- migrate up the respiratory tract to the epiglottiso They crawl over epiglottis to pharynx and are swallowed
  10. 10. o In jejunum, they moult and develop a temporary buccal capsule-get attaches to guto Feed and grow in size, undergo 4th and final moulting, develop buccal capsule and grow into adultso From time of infection, it takes 6 wks for the worm to become sexually matureo Rarely infection occurs through buccal routeo Transmammary and transplacental transmission has been reported
  11. 11. LIFE CYCLE OF ANCYLOSTOMA
  12. 12. NECATOR AMERICANUSMORPHOLOGYo Adult worms are slightly smaller than A.duodenaleo Male 7-9 mm long and 0.3mm thicko Female 9-11mm long and 0.4mm thicko Anterior end is bent in the opposite direction of general curvature of bodyo They have a smaller buccal capsule with two pairs of semilunar cutting plates
  13. 13. o Copulatory bursa is long and wideo Copulatory spicules are fused at the ends to form a barbed tipo In the female vulva is placed in the middle of the bodyo Eggs are identical with those of A.duodenaleo Life cycle is also similar. Life span is much longer about 4-20 yrso 2-7 yrs in A duodenale
  14. 14. necator
  15. 15. 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 DORSALLYCOPULATOR THE DORSAL RAY IS SINGLE HAS A PAIRED DORSAL RAY WITH A SPLIT END Y BURSACOPULATOR SEPERATE FUSED AT TIP Y SPICULES
  16. 16. PATHOGENESIS AND CLINICAL FEATURESo When filariform larva enters the skin, they cause severe local itchingo Erythematous papular rash may developo Scratching and secondary bacterial infection may followo This condition is called Ground itch, occurs when large number of larvae penetrate the skin, more common with necatoro Larvae sometimes cause creeping eruption- more common in animal hookworms
  17. 17. • Larvae migrate between stratum germinativum & S. corneumserpi genous vesicular lesion
  18. 18. o When larvae enters the alveoli, they may cause minute local haemorrhages.o Clinical pneumonitis develops only in massive infectionso Important manifestations of ancylostomiasis is in the intestineo Worms attach to gut mucosa by their buccal capsuleso Suck a portion of intestinal villi, utilise gut epithelial cells and plasma for their foodo The worm sucks in blood, which passes out undigested through its intestineso Adult ancylostome can suck about 0.2ml blood and necator sucks 0.03ml per dayo The worms frequently leave one site and attaches to another site
  19. 19. o Bleeding from the site continue for sometime due to the anticoagulant activity of the secretions of the wormo Blood loss over a period of time leads to microcytic hypochromic iron deficiency anaemiao Degree of anaemia is directly proportional to worm burdeno Worm loads upto 100 worms cause no symptoms,500-1000 or more cause significant blood loss and anaemiao 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
  20. 20. o In hookworm disease, intestinal absorption of iron is normal so oral administration of iron can correct anemiao 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 stageo Anaemia leads to lassitude and dullness, hypoprotenemia etco Severe hookworm anemia leads to cardiac failure
  21. 21. DIAGNOSISo Demonstration of eggs in faeces by direct microscopy or by concentration methodso Rhabditiform larvae may present in samples which are examined 24 hrs or more after collection TREATMENTo MEBENDAZOLEo PYRANTEL PAMOATEo THIABENDAZOLE is less effectiveo BEPHENIUM HYDROXYNAPHTHOATE is active against Ancylostoma but not against Necator
  22. 22. EPIDEMIOLOGY AND PREVENTIONo Conditions required for maintenance of endemic hookworm infection are2. Presence of infected persons3. Dispersal of eggs in soil4. Appropriate environmental factors facilitating development of eggs5. Opportunity for the larvae to infect people through exposed skin surfaceo These conditions prevail throughout the year-in tropics but in subtropics it exist only seasonally-in warmer monthso Prevention of SOIL POLLUTION WITH FAECES,USE OF FOOTWEAR,GLOVES,TREATMENT OF PATIENTS AND CARRIERS etc can limit the infection
  23. 23. THANK YOU

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