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/