寄生虫大题6页

1、Parasites harms on man (1)Depriving the host of nourishment: example, hookworms suck blood. (2)Mechanical effects of parasites on host tissues and organs: example, biliary ascariasis and larva migrans. (3)Toxic effect: Arthropods introduce toxin into the host skin, inducing the host local and system

2、ic reactions. Example, mosquitoes, spiders and ticks introduce venom when they insert their mouth parts into the skin. (4)Immuno-pathological lesion: example, schistosoma liver cirrhosis; when hydatid fluid is released from the rupture of a hydatid cyst anaphylaxis often results.2. Characteristics o

3、f Class Nematode (1)Body is non-segmented, elongate, and circular in cross-section. (2)Two sexes are separated. is larger with a straight tail and a double set of reproductive organs. is smaller with a curled tail and a single set of reproductive organs. (3)Digestive tract (system) is complete. (4)T

4、he body cavity is a protocoele(原体腔). (5)Life cycle: infective stage is embryonated egg or larva3. Egglarva (several stages)adolescentadult Factors favoring the ascarid spread (1)Simple life cycle. (2)Enormous egg production ( 240,000 eggs/ day/ female ). (3)These eggs are highly resistant to ordinar

5、y disinfectants( due to the ascroside). The eggs may remain viable for several years. (4)Social customs and living habits. (5)Disposal of feces is unsuitable.Enterobius vermicularis(pinworm)An clinical case The major symptom is anal itch, which is associated with the noctural migration of the gravid

6、 females from the anus and deposition of eggs in the perianal folds of the skin. Diagnosis: Cellophane tape technique is first choice. The examination should be made in the morning, before the patient has washed the anus or defecated.Drugs: Albendazole or mebendazole are very effective. Since life s

7、pan of pinworm is about one mouth, the major problem is re-infection. Repeated treatment may be necessary for a radical cure. 5. Life cycle of ascarid and whipworm Ascaris lumbricoides Trichuris trichiuraSite of inhabitationUpper part of small intestineIleocecum Infective stageEmbryonate eggsEmbryon

8、ate eggsRoute of infectionBy mouthBy mouthIntermediate hostNo No Egg output240000/day5000/dayLife spanAbout 1 yearAbout 35 yearsFeeding habitsIntestinal contentsBlood , Tissue fluidMigration Yes No Others Boring habits: going deep into the openings of other organs on the intestinal wallParasitizing

9、mode: the slender head goes deep into the intestinal mucosaHow do hookworms cause anemia It results from hookworms sucking blood and excessive blood loss. The excessive blood loss is due to the large worm burden; worms secreting several antiagglutinating materials (antiagglutinin, etc.), often chang

10、ing the place to suck blood and discharging undigested blood; the old injured sites of the intestinal wall continuing to bleed. The other reason for the anemia is that the patient can not get enough noutrition. Factors favoring the hookworm spread (1)simple life cycle. (2)pollution of the soil by fe

11、ces containing enormous hookworm eggs. (3)warm and moisture climate is favorable for the development of hookworm eggs and larvae. (4)human gets infection by skin contacting with the infective larvae in fertilized soil or on plants. The hookworm incidence of farmers is the highest.Life cycle of ascar

12、id and hookwormAscaris lumbricoides Hookworm Site of inhabitationUpper part of small intestineUpper part of small intestine Infective stageEmbryonate eggsL3/ filariform larvaRoute of infectionBy mouthBy skinIntermediate hostNo ( geohelminth )No ( geohelminth ) Final hostHuman Human Egg output240000/

13、day1000030000/Ad/day500010000/Na/dayLife spanAbout 1 yearAverage 3 yearsFeeding habitsIntestinal contentsBloodBlood-lung Migration Pass through the liver In lungs of host, larvae molt twice and stay in the lung for 10days Dont pass through the liver the larvae dont molt and stay in the lungs Nocturn

14、al periodicity and its clinical significance The microfilariae present in the peripheral blood during daytime is very low in density. The number of microfilariae gradually increase from evening to midnight. The phenomenon is called nocturnal periodicity. In diagnosis of filariae, first choice method

15、 is thick blood smear, taking blood during the night from 10 pm to 2 am. The confirmative diagnosis depends on the demonstration of the microfilariae in peripheral blood during the night from 10 pm to 2 am.Common Features about Trematoda (1)Most adult trematodes are dorso-ventral flattened, bilatera

16、lly symmetric, leaf-like or tongue-like covered with spines or tubercles. (2)Armed with an oral sucker and a ventral sucker. (3)The digestive tract is degenerate. The end of intestine is a cecum without anus. (4)The reproductive system is developed and hermaphroditic. (5)Eggs of most species have an

17、 operculum (lid) and /or a small spine (knob). The developed egg contains a miracidium. (6)They are biohelminths. Eggs continue to develop in fresh water. Their intermediate hosts are in water. 1st intermediate hosts are all snails; 2nd intermediate hosts varies from species. (7)Typical life cycle o

18、f the digenetic trematodes include sexual generation and asexual generation(Digenesis /Alternation of generations) (8) Life cycle model: sexual reproduction get into fresh water in the 1st int. hostAdult eggs miracidiae sporocysts asexual reproduction radiae cercariae metacercariae(the 2nd int. host

19、) (9)Infective stage is usually a metacercaria (10)They have their reservoir hosts. The fluke diseases are zoonoses.Epidemiological survey of Clonorchis sinensis (1) int. hosts (snail, fish, shrimp) (2) reservoir hosts (3) discovery of patients and carriers (4) habits of eating raw fish (5) mode of

20、raising fish (6) mode of stool disposalWhy Schistosoma japonicum is a special fluke (1)The adult worms look like nematodes, elongated cylindrical in shape. (2)Two sexes are separate (dioecism). (3)Egg without operculum, with a lateral spine. (4)Only one intermediate host required. (5)The infective s

21、tage is cercaria. (6)The infective route is by skin. (7)The eggs are main pathogenic stage. (8)Adults live in the blood vessels.13. Whats the clinical manifestations of Schistosomiasis in acute stage and terminal stage (1) Acute stage: The characteristics symptoms is dysentery. The patient may pass

22、stool with blood, pus and mucus 5-10 times per day, in which a large number of eggs can be found. Chill, fever, and malaise occur. (2)Terminal stage is characterized by portal vein hypertension syndrome. (common saying, abdomen distention looks like a big drum, emaciation looks like a fire wood). As

23、cites, emaciation, varicosity, splenomegaly and anemia are commonly found. The patients die of secondary infection, upper digestive tract bleeding, hepatic coma.Common features of Class Cestoda (1)Adult worm is flattened ribbon-like, without body cavity. (2)The body is composed of a head, neck and s

24、egmented strobile (链体). The head consists of attachment organs including suckers, rostellum (顶突) and hooklets or sucking grooves. The neck is the budding zone from which segments are formed. The strobile (a chain of segments) consists of immature, mature and pregnant proglottides. (3)They are hermap

25、hroditic. There is a set of female and male reproductive organs in every mature proglottides. (4)Digestive tract is absent. Nutrition is absorbed by villi of body surface. (5)They are biohelminths. Intermediate hosts are indispensable. (6)All adult worms parasitize digestive tracts of mammals. (7)Th

26、e developing stages in intermediate hosts are called metacestode (中绦期), such as cysticercus (囊尾蚴), hydatid cyst (棘球蚴), cysticercoid.Transmission, diagnosis and treatment of Taenia solium Transmission: by eating raw bean-pork Diagnosis:(1)Taeniasis: Confirmative diagnosis of taeniasis is made by find

27、ing gravid proglottides or egg in stool.Looking for gravid proglottids in stoolLooking for eggs in stool(direct fecal smear; brine floatation method) (2)Cysticercosis: Biopsy of subcutaneous nodulesX-ray , Computerized tomography (CT) and magnetic resonance (MR) are used for the diagnosis of brain t

28、ype. EQ oac(,3)Ophthalmoscope examination is used for ocular form.Treatment:(1)Chinese herb medicine:pumpkin seed, areca nut and MgSO4. (2)Praziquantel may be used.16. Person who has taeniasis and the people around him are easier to have cysticercosis, why? The principle of taeniasis treatment. (1)T

29、he eggs of T. Solium can infect human and develop to cysticercus, causing cysticercosis. But it cant develop to adult. People are infected by eggs through three pathways:endo-auto-infection exo-auto-infection EQ oac(,3)foreign infection (2)Principles: Pork taeniasis should be diagnosed and treated a

30、s early as possible and treated thoroughly. The recognition of a scolex in the patients stool after the application of taenifuge is important.Which is more harmful to man between pork tapeworm and beef tapeworm? Why? The lesion of T. Solium is more severe. (1)T. Saginata only causes taeniasis; T. So

31、lium causes taeniasis and three type of cysticercosis.(subcutaneous type, ocular type, brain type) (2)Both of them parasite in the intestine, causing injure to mucosa of intestine. But because of the rostellum and hooklets, T. Solium cause more severe injure to the mucosa.Pathogenic mechanism of pro

32、tozoa (1)Damage by proliferation of protozoa.e.g.Plasmidium vivax (2)Damage by of diffusion of protozoa.e.g.Entamoeba histolytica (3)Damage by toxin.e.g.Entamoeba histolytica. (4)Damage by opportunistic protozoa: The protozoan living in the human body in commensalisms make the host attack when his i

33、mmunity is lower or restrained, such as Pneumocystis and Toxoplasma gondii.Whats opportunistic protozoa, give an example.(Refer to )Female patient, 33 years old, peasant. She has passed the jam-like stool with a foul smell, 4-5 times daily, and fatigued for 7 days. She has a pain in the lift-low abd

34、omen, but her abdomen is soft and temperature 38C, pulse 90 times/m. (1)What kind of disease may the patient be ill with? Amoebic dysentery. (2)What kinds of laboratory examination and evidence can be used to confirm your diagnosis? 1)living trophozoite in unformed feces:direct fecal smear with NS.

35、One must pay attention to: EQ oac(,1)The container must be clean and free of acid or alkali. The feces should be examined soon after it has been passed. EQ oac(,3)Keep specimen warm in order to keep the trophozoites activity. EQ oac(,4)Select the bloody and mucous portion for examination. EQ oac(,5)

36、The stool examination must be done before taking medicine and pay attention to looking for Charcot-Leyden crystals. 2)Cyst: direct fecal smear with iodine stain. (3)What drugs should be used for the radical cure of the disease? Metronidazole (甲硝咪唑或灭滴灵) or tinidazole(替硝唑).21. Five major characteristi

37、cs of visceral leishmaniasis (1)Irregular fever for long period. (2)Hepato-splenomegaly and enlargement of lymph node. (3)Anemia. (4) Bleeding and infection. (5) Ratio of albumin to globulin is inverted.What are the route of infection, the principle and method of diagnosis and treatment of Trichomon

38、as vaginalis? Infective route: by sexual intercourse or some indirect ways Principle: find trophozoites In women:vaginal discharges In men: prostatic fluid or urine Method: direct smear or culturing methods Treatment: Both the patients and carriers should be treated. Metronidazole (灭滴灵) Tinidazole (

39、替硝唑)Explain clinical roles of stages of plasmodium vivax life cycle Exoerythrocytic stage: incubation period; treatment; relapseErythrocytic stage: typical attack(paroxysm); diagnosis; treatment; recrudescence Gametocyte stage: transmissionSporozoite stage(in mosquitoes): transmission; infective sta

40、geThe typical attack of malaria Typical attack: paroxysm (810 hrs). Each paroxysm shows a succession of three stages: (1)The cold stage (chill): the attack begins with a sudden shaking chill, lasting for 12 hrs. (2)The hot stage (fever) is generally over 39C, lasting 46 hrs. (3)The sweat stage: swea

41、ting brings down the fever. P. v, P. f and P. o: once 48 hrs; P. m: once 72 hrs The attack occurs because of the sudden liberation of merozoites, malarial pigment and RBC debris into the blood stream.Recrudescence and relapse of malaria Recrudescence occurs when the blood schizonticide doesnt elimin

42、ate all parasites from the blood stream, either because the dose was inadequate or because the parasite is resistant to the drug. Relapse occurs in P. vivax and P. ovale infections after the delayed development of liver stage parasites (bradysporozoite) that have not been treated adequately with a t

43、issue schizonticide. P. Falciparum and P. Malariae have only recrudescence, but P. v and P. o have both relapse and recrudescence. Remnant of parasites in RBC results in recrudescence. Bradysporozoites (or called hypnozoites) in liver cause relapse.Principles of treatment of malaria (1)Chloroquine(氯

44、喹) eliminates the erythrocytic parasites to stop malarial attackingcontrol of clinical symptoms (2)Primaquine(伯氨喹啉) eliminates the exo-erythrocytic parasites and the gametocytes to prevent malarial relapse and transmission. (3)Artemisinin (青蒿素) is most effective against the erythrocytic stage, so it

45、 is useful to the parasites with resistance to chloroquine.Infective routes of Toxoplasma gondii, which is the most important, why? (1)Congenital transmission(Transplacental transmission) (2)Postnatal transmission: by mouth, blood, skinCongenital transmission is the most important route of infection

46、. It usually take place in the course of acute but inapparent or undiagnosed maternal infection. The damage: 1)Fetus: abortion, dead birth, small brain and hydrocephalus (脑积水). Intense proliferation of tachyzoites in the brain damages large areas and may cause death. 2)Infants: hydrocephalus, cerebr

47、al calcified focus, retinal inflammation and handicapped mentally and/or physically.Characteristics of arthropods (1)Metamerism (2)Exoskeleton (3)Bilateral Symmetry (4)Jointed Appendages (5)Open Circulatory System (6)Ventral Nerve CordWhat are medical arthropods harms to man? (1)Direct harm:1)Annoya

48、nce-flies interfere with your work and rest. 2)Venom-stings of scorpions and spiders may even cause death. 3)Parasites-Fly larvae may cause myiasis; scabies and mange are caused by Sarcoptes scabiei. (2)Transmission of diseases: 1)Mechanical transmission. 2)Biological transmission: Pathogens spend a

49、 part of their life cycle in the arthropods. Propagative; Cyclopropagative; Cyclodevelopmental; TransovarianHow verify an arthropod which can biologically transmit a disease? (1)Propagative: arthropods act like culture media for the pathogens. E.g. Yersinia pestis multiply in fleas. (2)Cyclopropagat

50、ive: The pathogenic organisms undergo a developmental cycle in the arthropod with multiplication and change in form. E.g. Plasmodium in anopheline mosquitoes. (3)Cyclodevelopmental: The pathogenic organisms undergo a change in form without multiplication. E.g. Filaria in mosquitoes. (4)Transovarian:

51、 The first generation gets the infection and the second generation spreads the disease. E.g. Encephalitis B virus in mosquitoes.Diseases transmitted by mosquitoes (1)malaria: Anopheles (2)filariasis: many kinds of Anopheles and Culex (3)virus disease: 1)dengue: Aedes aegypti & Aedes albopictus 2)yel

52、low fever: Aedes 3)encephalitis: many kinds of Aedes and CulexDescribe mosquitoes breeding places and give examples (1)Big fresh water as rice fields, ponds: Anopheles sinensis (2)Small water bodies and containers as jars, earthware, tree hole: Aedes albopictus (3)Polluted waters as stagnant or dirt

53、y ponds: Culex pipiens pallens (4)Running water as stream: Anopheles minimus (5)Water body of jungle forest type as stone hole or spring in jungle: Anopheles dirusWhich medical arthropod is most harmful to man? Why?(Why do mosquitoes play the most important role in medical arthropods?) (1)Mosquitoes have many species and widely spread; have close relationship with human; have drug resistance; hard to control (2)Mosquitoes and diseases: 1)Annoyance pest: A mosquit