病原生物学英文课件：Nematodes

1、Important Groups of Human Parasites,Helminthes Nematode Trematode Cestode,Protozoa Amoeba Flagellate Sporidium Ciliate,Arthropoda Mosquito Fly Tick Mite Bug Flea Lice,Helminthes（蠕虫）,Nematode（线虫）,Trematode （吸虫）,Cestode （绦虫）,Objectives,掌握蛔虫、钩虫、蛲虫、鞭虫的成虫和虫卵的形态特征。 掌握蛔虫、钩虫、蛲虫、鞭虫、丝虫、旋毛虫的生活史、致病性及其感染的诊断方法。 熟

2、悉丝虫微丝蚴和旋毛虫幼虫囊包的形态特征。 熟悉粪类圆线虫、广州管圆线虫的致病性与诊断方法。熟悉常见线虫的流行特点和防治原则。 了解常见线虫的分布特点。 了解粪类圆线虫、广州管圆线虫的形态特点。,Introduction of Nematodes,Generally cylindrical, tapered at both ends. Complete digestive tract with both oral and anal openings. Diecious: the sexes are separated; generally males are much smaller than

3、female worms. The majority of nematodes are free living; a dozen or more are parasites.,Nematodes,The intestinal nematodes Ascaris Hook worm Pin worm Whip worm Stronglyloides stercoralis,The blood- and tissue dwelling nematodes Filaria Trichinella worm Angiostrongylus cantonensis,Ascaris lumbricoide

4、s似蚓蛔线虫,Ascaris蛔虫,Species name,Genus name,Introduction,Giant roundworm The first representative and the most common intestinal parasite in humans Cosmopolitan in distribution, 25% humans are infected with this parasite. Has highest prevalence in area of poor sanitation and where human feces are used

5、as fertilizer. (Rural Urban; Children Adults),Morphology,Adult worms Looks like an earthworm Cylindrical shape, creamy white or pinkish in color Female, average 20-35 cm in length Male, average 12-30 cm and is more slender than female.,A pair of female and male worms of A. lumbricoides. Notice the v

6、ulvar 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”,Eggs Fertilized egg (受精卵） Unfertilized egg (未受精卵),Albuminous layer,Egg shell,Ovum,Rounded with the size 40-75 m in length. Has a thick shell with a

7、n albuminous layer Brownish in color (stained by bile) A big round ovum inside,Ascaris lumbricoides, fertilized egg,What does this egg look like?,A decorticated fertilized egg of A. lumbricoides,Ascaris lumbricoides, unfertilized egg,Elongated and larger than fertile eggs (up to 90 m in length) Egg

8、shell and albuminous layer are thinner Brownish in color (stained by bile) Yolk granules inside,Unfertilized and Fertilized Eggs of Ascaris Lumbricoides,Ascaris lumbricoides, infective egg,Larva,The Life cycle of Ascaris lumbricoides,Living site Adults in small intestine,Diagnostic stage Undeveloped

9、 eggs in feces,Infective stage Eggs embryonate in soil by 2-3 wks,Method of infection Infective eggs are ingested,Migration Larvae migrate though the lungs,HOST MAN,Larvae of Ascaris lumbricoides in lung,Ascaris lumbricoides adults in small intestine,Symptoms/Pathology,Adults The presence of few wor

10、ms may be asymptomatic (85%) Symptoms might include Vague abdominal pain Diarrhea Fever Nausea Stomach ache Vomiting weakness,Large numbers of worms may cause malnutrition (slower growing of a child or a teen) and signs and symptoms of obstruction,A large mass of Ascaris lumbricoides that was passed

11、 from the intestinal tract. The ruler at the bottom of the image is 4 cm (about 1.5 inches) in length.,Bowel obstruction caused by Ascaris lumbricoides,Migration of adult worms may cause signs and symptoms of perforation, peritonitis, appendicitis or extrahepatic biliary obstruction.,Ascaris lumbric

12、oides perforates the intestine.,Ascaris 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,Peritonitis caused by intestinal perforation due to Ascaris,Re

13、sected bowel and the adult female from the peritoneal cavity,Larva Pneumonitis Asthma attacks Loefflers syndrome The respiratory phase of ascariasis, marked by inflammation of the lungs and eosinophilia.,Diagnosis,Microscopic identification eggs in the stool. A direct wet mount examination of the sp

14、ecimen (240,000 eggs/female/day) Macroscopic identification of adults passed in stool or through the mouth or nose,Epidemiology,Worldwide distribution, throughout the temperate and tropical areas 1,000,000,000 people in the world 22% population in Africa and Asia 12.72%, 85,930,000 in China (2001-20

15、04),Treatment,Albendazole (阿苯哒唑)a single oral dose of 400 mg Mebenazole (甲苯哒唑)100 mg orally twice daily for 3 days,Prevention,Avoid contacting soil that may be contaminated with human feces Do not defecate outdoors Dispose of diapers properly Wash hands with soap and water before handling food When

16、traveling to areas where sanitation and hygiene are poor, avoid water or food that may be contaminated Wash, peel or cook all vegetables and fruits before eating,Trichuris trichiura毛首鞭形线虫,Whip worm鞭虫,Introduction,A soil transmitted nematode parasite Cause trichuriasis (鞭虫病) Infects over 800 million

17、people Found predominantly in tropical climates under condition of poor sanitation Trichuris and Ascaris are often coexistent One of the most successful parasites of mammals,Morphology,Adult worm Median size Thin anterior end and thick posterior potion (Whip) Egg Spindle shaped with two plug-like pr

18、ominence at two poles,Trichuris trichiura adults.,Trichuris trichiura egg. (yellowish brown, barrel - shaped with thick egg shell and mucoid plug at either end),Life Cycle,Similar to Ascaris but no pulmonary migration Developmental cycle shorter (1 month) Favorable site: ileo-caecal region Firmly in

19、serted into the mucosa (more difficult to be expelled),Pathogenesis,Adult Local inflammation Filariform larva,Intra-human development Infective larva penetrate skin Migration via lung 5-7 weeks mature Life span 5-7 years,Pathogenesis,Larva Dermatitis ground itch(skin penetration larvae) Pneumonitis

20、and Bronchitis(larval migration through the lung),Cutaneous larva migrans (CLM) of the Foot,Adult (Hookworm infection D shaped Transparent Thick transparent shell Tadpole-like embryo when discharged,Main points of life cycle,Direct type (geo-helminth) Inhabit: Colon Gravid female adult deposits its

21、eggs on the anus and perianal skin Egg takes 6 hours to be infective stage,Infective stage: Infective egg Mode: Anus-Hand-Mouth Auto-infection Cross-infection Intro-infection Life span:Female 2 months,Adult female worms are seen in the perianal region,Pathogenesis,Anal itching (migration of gravid f

22、emales) Digestive disturbances Ectopic infection Vaginitis Endometritis Salpingitis,Laboratory Diagnosis,Collect eggs from perianal region by anal swab or transparent cellophane tape (immediately after waking up). Search adult female in the perianal region when the child is sleeping (2-3 h after fal

23、ling asleep.,Prevention and Control,Readily endemic in children concentrated units Mebendazole (100mg repeated after 2 weeks) Should put the prevention in first Keep finger out of mouth and nose Keep fingernails short and do not bite them Wash hands after using the toilet and before eating Change cl

24、othing, towels, and sheets frequently, and wash them in hot wather,Cross-infection,Ova contaminate the environment,Inhalation of airborne,The Blood- and Tissue- Dwelling Nematodes,Filarial worm Trichina worm,Common Characteristics,Biohelminth Need intermediate host Location (residing site) Tissue an

25、d blood Ovoviviparous (larviparous) Adult female deposits larvae,The Filariae,2 types of filaria Lymphatic filaria Tissue filaria Subcutaneous tissue (O.volvulus, L.loa) Peritoneal cavity (D.perstans) All species are transmitted by insect vectors 8 species could infect human being,Most Important Spe

26、cies,Tissue filaria Onchocerca volvulus: river blindness Loa loa: subcutaneous swelling Lymphatic filaria W. Bancrofti B. Malayi,Wuchereria bancrofti班氏吴策线虫Brugia malayi马来布鲁线虫,Morphology,Adult Threadlike white worm W.b B.m,Microfilaria (Mf) Appears in host peripheral circulation during night Structure Sheath: thin and delicate; surrounds the embryo Embryo: cylindrical; bluntly rounded anteriorly; tapers to a point posteriorly Cephalic space Somatic nuclei Caudal nuclei,Differentiation of Mfs Between W.b and B.m,Microfilaria of Wuchereria ba