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NematodeThe intestinal nematodesAscarisHook wormsPin wormWhip wormThe blood- and tissue dwelling nematodesThe filariaTrichinella
Ascaris
Ascaris lumbricoides
IntroductionThe first representative and the most common intestinal parasiteCosmopolitan in distributionRural > urbanChildren > adults
MorphologyAdultLooks like an earthwormFemale (20-35 cm); Male (12-30 cm)3 lips which carry minute teeth
A pair of female and male worms of A. lumbricoides. Notice the vulvar waist(arrow)of the female worm and the coiled end of the male worm.
A scanning electron micrograph of Ascaris showing the three prominent lips
EggFertilized eggUnfertilized egg
Albuminous layerEgg shellOvum A. lumbricoides, fertilized egg (6050 micrometer)
A. lumbricoides, fertilized egg
A. lumbricoides unfertilized egg
The life cycle of A. lumbricoides
Living siteAdults in small intestineDiagnostic stageUndeveloped eggs in fecesInfective stageEggs embryonate in soil by 2-3 wksMethod of infectionInfective eggs are ingestedMigrationLarvae migrate though the lungsHOSTMAN
SymptomatologyLarvaPneumonitisAsthma attacksLoefflers syndrome
AdultThe presence of few worms may be asymptomatic (85%)The most common symptoms are vague abdominal painLarge numbers of worms may cause malnutrition and present signs and symptoms of obstruction
Migration of adult worms may cause signs and symptoms of perforation, peritonitis, appendicitis or extrahepatic biliary obstruction.
A.lumbricoides in common bile duct
Cross section of a liver specimen contains many adult worms of A.lumbricoides obstructing the intrahepatic and extrahepatic bile ducts.
Ascarid chronic pancreatitis
A large mass of Ascaris lumbricoides that was passed from the intestinal tract. The ruler at the bottom of the image is 4 cm (about 1.5 inches) in length.
An autopsy specimen shows intestinal obstruction by many adult worms of A.lumbricoides. Notice the markedly distended intestinal loop, the thin intestinal wall with hemorrhage and worms protruding from the perforated wound.
Peritonitis caused by intestinal perforation due to Ascaris Resected bowel and the adult female from the peritoneal cavity
DiagnosisMicroscopic identification eggs in the stool a direct wet mount examination of the specimen (200,000 eggs/female/day)Macroscopic identification of adults passed in stool or through the mouth or nose
Epidemiology Worldwide distribution, throughout the temperate and tropical areas1,000,000,000 people in the world40% population in Africa and Asia600,000,000 in China (1992)
TreatmentAlbendazole a single oral dose of 400 mgMebenazole 100 mg orally twice daily for 3 days
PreventionAvoid contacting soil that may be contaminated with human fecesDo not defecate outdoorsDispose of diapers properly
Wash hands with soap and water before handling foodWhen traveling to areas where sanitation and hygiene are poor, avoid water or food that may be contaminatedWash, peel or cook all raw vegetables and fruits before eating
Hook worms
Ancylostoma duodenaleNecator americanus
PinwormEnterobius vermicularis
Whip wormTrichuris trichiura
Adult worms of Ancylostoma duodenale
Adult worms of Necator americanus
MorphologyAdultCylindrical with the head bent sharply backwardsMales are smaller than the females and possess a bursa at their posterior end
Scanning electron micrograph of the oral opening of Ancylostoma duodenale, another species of human hookworm. Note the presence of four cutting "teeth," two on each side.
Adult mouthpart of Necator americanusNote : The large buccal capsule is open dorsally with one pair of cutting plate teeth.
Bursa of hookworms Lift A. duodenale; Right N. americanus
A.dN.aSizeLargerSmallerShapeCSBuccal capsule4 hooklets2 platesBursaRound BroaderDorsal ray Tridigitate at the terminusBidigitate at the baseSpiculesSeparatedFused at terminalMucron PresentAbsence
Enterobius vermicularis adult female0.8-1.3cm.in length , spindle-shaped with a long thin sharply tail. The greater part of the body is occupied by the uterus filled with eggs.
Trichuris trichiura adults.
Egg (indistinguishable between the 2 species)Median size (like the ascaris egg)EllipticalTransparentThin shell4-cell stage when discharge
Enterobius vermicularis egg. Note the thick shell and characteristic shape; approximate length = 55 m.
Egg< Ascaris eggNon-symmetrical ellipse; D shapedTransparentThick transparent shellTadpole-like embryo when discharged
Trichuris vulpis egg
Life CycleHost -manNo intermediate host : Egg Larva (free-living) Larvae migrate from skin to the lungs :Egg takes 6 hours to be infective stage : Similar to Ascaris but no pulmonary migration . There are reservoir hosts.
Parasitic site: : small intestinal : upper small intestine; Duodenum, jejunum : colon Gravid female adult deposits its eggs on the anus and perianal skin. : ileo-caecal region
Infection stage : infective egg : infective larva : infective egg ( Egg takes 6 hours to be infective stage) infective mode: Anus-Hand-MouthAuto-infection/Cross-infection : infective egg
Pathogenic stage: : adult worm /larva :adult worm Digestive disturbances /Allotriophagy Microcytic hypochromic anemia (sucking, oozing, discharging) A.d. 0.15-0.4ml/d; N.a. 0.02-0.1ml/d larva:Dermatitis ground itch Pneumonitis and Bronchitis
Pathogenic stage: :adult worm Anal itching (migration of gravid females) Ectopic infection Digestive disturbances :adult worm Digestive disturbances Anemia
Trichuris trichiura in the large intestine. Many worms are present, each with its anterior end embedded in the intestinal mucosa, resulting in the erythema.
Etiologic dignosis: :fecal direct smear :Brine floatation Larva cultivation Egg counting(to estimate infection intensity) : Collect eggs from perianal region by anal swab on the cellophane tape. Search adult female in the perianal region when the child is sleeping. : Brine floatation
Prevention and Control:Distribution Cosmopolitan 0.4 billion humans are infected in ChinaNatural factorsSoil contaminationNight soil as fertilizerSuitable climate dry-land vegetable- raising & mine
Prevention and ControlReadily endemic in children concentrated unitsShould put the prevention in firstMebendazole (100mg repeated after 2 weeks) Principles same as for ascaris
Drug: Albendazole 400mg/d // Mebendazole 100mg/ 2/d 3 (600mg repeated after 2 weeks)
*http://www.dpd.cdc.gov/dpdx/HTML/Search_Choices.htm*http://www.biosci.ohio-state.edu/~parasite/ascaris.html*http://www.biosci.ohio-state.edu/~parasite/ascaris.html*http://www.biosci.ohio-state.edu/~parasite/ascaris.html*http://www.dpd.cdc.gov/dpdx/HTML/Search_Choices.htm*http://www.biosci.ohio-state.edu/~parasite/ascaris.html*http://www.life.sci.qut.edu.au/LIFESCI/darben/figs/nematode/intnema/aduodmf.jpg*http://www.life.sci.qut.edu.au/LIFESCI/darben/figs/nematode/intnema/aduodmf.jpg*http://wwhttp://www.biosci.ohio-state.edu/~parasite/hookworm_adults.html*http://www.medicine.cmu.ac.th/dept/parasite/official/nematode/framene.htm*http://www.medicine.cmu.ac.th/dept/parasite/official/nematode/framene.htm0.8-1.3 cm.in length , spindle-shaped with a long pointed posterior end. Anterior part has dorsoventral bladder-like expansions of cuticula (cervical alae). Rhabditiform esophagus. The greater part of the body is occupied by the uterus filled with eggs.
*http://www.biosci.ohio-state.edu/~parasite/trichuris.html*http://www.biosci.ohio-state.edu/~parasite/enterobius.html
*http://www.biosci.ohio-state.edu/~parasite/trichuris.html*http://www.dpd.cdc.gov/dpdx/HTML/ImageLibrary/Hookworm_il.htmThe third stage larva initiates the infection by penetrating the shin and passing into the blood circulation,. Through the blood it is carried to the right heart and then to pulmonary blood vessels. It soon breaks out of the pulmonary blood vessels into the alveoli. It then crawls up the trachea and is is swallowed with saliva to re-enter the intestinal tract.*http://www.biosci.ohio-state.edu/~parasite/trichuris.htmlErythema /erithi:ma/