10A. lumbricoides, fertilized egg A. lumbricoides, fertilized egg
11A. lumbricoides unfertilized egg A. lumbricoides unfertilized egg
12The life cycle of A. lumbricoides The life cycle of A. lumbricoides
13HOST MAN Living site Adults in small intestine Migration Larvae migrate though the lungsDiagnostic stageUndeveloped eggs in fecesMethod of infectionInfective eggs are ingestedInfective stageEggs embryonate in soil by 2-3 wks
18Cross section of a liver specimen contains many adult worms of A Cross section of a liver specimen contains many adult worms of A.lumbricoides obstructing the intrahepatic and extrahepatic bile ducts.
20A 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.
21An 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.
22Peritonitis caused by intestinal perforation due to Ascaris Resected bowel and the adult female from the peritoneal cavity
23DiagnosisMicroscopic 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
24EpidemiologyWorldwide distribution, throughout the temperate and tropical areas1,000,000,000 people in the world40% population in Africa and Asia600,000,000 in China (1992)
25Treatment Albendazole a single oral dose of 400 mg Mebenazole 100 mg orally twice daily for 3 days
26PreventionAvoid contacting soil that may be contaminated with human fecesDo not defecate outdoorsDispose of diapers properly
27Wash hands with soap and water before handling food When 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
32Adult worms of Ancylostoma duodenale Adult worms of Ancylostoma duodenale
33Adult worms of Necator americanus Adult worms of Necator americanus
34Morphology Adult Cylindrical with the head bent sharply backwards Males are smaller than the females and possess a bursa at their posterior end
35http://wwhttp://www. biosci. ohio-state. edu/~parasite/hookworm_adults 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.
36Adult mouthpart of Necator americanus Adult mouthpart of Necator americanusNote : The large buccal capsule is open dorsally with one pair of cutting plate teeth.
37Lift A. duodenale; Right N. americanus Bursa of hookwormsLift A. duodenale; Right N. americanus
38Tridigitate at the terminus A.dN.aSizeLargerSmallerShape“C”“S”Buccal capsule4 hooklets2 platesBursaRoundBroaderDorsal rayTridigitate at the terminusBidigitate at the baseSpiculesSeparatedFused at terminalMucronPresentAbsence
39Enterobius vermicularis adult female 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.Enterobius vermicularis adult femalecm.in length , spindle-shaped with a long thin sharply tail. The greater part of the body is occupied by the uterus filled with eggs.
46The 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.
47Life Cycle Host -man No intermediate host 钩虫: Egg Larva (free-living) Larvae migrate from skin to the lungs蛲虫:Egg takes 6 hours to be infective stage鞭虫: Similar to Ascaris but no pulmonary migration . There are reservoir hosts.
48Parasitic site: 蛔虫: small intestinal 钩虫: upper small intestine; Duodenum, jejunum蛲虫: colonGravid female adult deposits its eggs on the anus and perianal skin.鞭虫: ileo-caecal region
49蛲虫: infective egg ( Egg takes 6 hours to be infective stage) Infection stage蛔虫: infective egg钩虫: infective larva蛲虫: infective egg ( Egg takes 6 hours to be infective stage)infective mode: Anus-Hand-MouthAuto-infection/Cross-infection鞭虫: infective egg
52Erythema /eri’thi:ma/ 红斑Trichuris trichiura in the large intestine. Many worms are present, each with its anterior end embedded in the intestinal mucosa, resulting in the erythema.
53Etiologic dignosis: 蛔虫:fecal direct smear 钩虫:Brine floatation Larva cultivationEgg counting(to estimate infection intensity)蛲虫: Collect eggs from perianal region by anal swab on the cellophane tape. Search adult female in the perianal region when the child is sleeping.鞭虫: Brine floatation
54Prevention and Control 钩虫:DistributionCosmopolitan0.4 billion humans are infected in ChinaNatural factorsSoil contaminationNight soil as fertilizerSuitable climate dry-land vegetable- raising & mine
55Prevention and Control 蛲虫Readily endemic in children concentrated unitsShould put the prevention in firstMebendazole (100mg repeated after 2 weeks)鞭虫Principles same as for ascaris