人體寄生蟲學(xué)：吸蟲

1、 吸蟲 Trematodes (Flukes)自學(xué)內(nèi)容華支睪吸蟲（考試范圍）布氏姜片吸蟲（考試范圍） 衛(wèi)氏并殖吸蟲（考試范圍）日本血吸蟲（考試范圍重點(diǎn)）Introduction to trematodesBelong to Phylum Platyhelminthes, (flatworms), Class trematoda.Trematodes (flukes), apart from schistosomes, all are hermaphroditic.Characteristics of Trematodes IThe hermaphroditic adults are flat

2、in ventral side and /or dorsal side.All adult contains an oral and a ventral sucker as holdfast organs.Flattened and leaf-shaped (Aside from the shistosomes) .Vary in length from a few millimeters to several centimeters. Characteristics of Trematodes IThe anterior sucker, the oral sucker, surrounds

3、the oral cavity, while the posterior sucker, ventral sucker is located on the ventral surface of the worm. Both attachment and locomotion.Oral suckerCharacteristics of Trematodes IIIncomplete digestive tract (oral sucker/ pharynx / esophagus / 2 cecum). Two cecum run parallel to each other, and end

4、blindly near the posterior extremity of the worm.Oral cavitypharynxesophaguscecum (gut)end of gutThe digestive system of flukeCharacteristics of Trematodes IIIThe body wall consists of two layers: cuticle （皮層） and an inner layer of muscle cells. The cuticle is cellular (syncytium，合體細(xì)胞).No body cavit

5、y. Characteristics of Trematodes IVMost of trematodes are hermaphroditic (important exceptions are the schistosomes), and some of them produce viable offspring by self-fertilizing, while others mainly by cross-fertilizing.Characteristics of Trematodes IVThe male reproductive system: 2 testes / 2 vas

6、 efferens （輸出管） / 1 vas deferens （輸精管） The female reproductive system: 1 ovary / 1 oviduct （輸卵管） / 1 seminal receptacle（受精囊）Oral suckerVentral suckerTestesOvaryUterusVas efferensCharacteristics of Trematodes VIndirect life-cycle1-2 intermediate host (the first intermediate host is snail)Reservior ho

7、stLarvae are hatched in waterApart form schistosomes (cercariae尾蚴), all infective stages are metacercariae (囊蚴). LarvaeMiracidium （毛蚴） : The first stage larva. They have cilia and swim about until they reach a snail. HatchWaterSporocyst （胞蚴） : The second stage larva. In the tissues of snail. It deve

8、lop into the next larval stage, redia （雷蚴） or daughter sporocysts. DevelopSnailsporocystRedia （雷蚴） : The third-stage larva. Redia develop in the body of snail and undergo a process of asexual reproduction, giving rise to many fourth-stage larvae, cercariae （尾蚴）.Develop(many)SnailCercaria （尾蚴） : The

9、final larval stage. It has tails but otherwise resemble the adults. They are released into water from the snail.Snail(many)WaterMetacercaria （囊蚴） : A mature form of the cercaria larvae of a fluke. Found in crayfish, fish, or crab (the second intermediate host).FishCrabThe important trematodesParagon

10、imus westermani (Lung flukes)Fasciolopsis buski (Intestinal flukes)Clonorchis sinensis (Liver flukes)Schistosoma japonicum mansoni Blood flukes haematobium衛(wèi)氏肺吸蟲Paragonimus westermaniIntroduction Worldwide in distribution.Human infections are confined mainly to oriental countries.Adult mainly harbor

11、in lung, sometimes also in brain, liver and abdominal wall.A number of animals can serve as reservoir host.Morphology - AdultAdult worms are 7.5-12mm long, 4-6mm width, 3.5-5mm thick.In life, they are reddish brown, like a semi-peanut.The oral and ventral suckers are equal, situated anteriorly and c

12、entrally respectively.The lobated testes are located posteriorly third of the body.The lobated ovary is found to the left of midline.The vitelline glandes（卵黃腺） are extensive in the lateral fields.Morphology - EggThey are yellow-brown, ovoid. 80118umX4860umA fertilized ovum and about tens yelk-cells

13、（卵黃細(xì)胞） in a thick shell.At the large end, the operculum is clearly visible.Life cycleThe first intermediate host: snail 川卷螺(melaniidae, Semisulcospira etc.).The second intermediate host: certain crayfish （蝲蛄） or freshwater crabs.Final host: human.Reservior host: carnivores (rat, dog, pig).Life cycle

14、Life cycleDevelopment in 1th intermediate host (snail)Eggs - the ciliated miracidia (water).Miracidium - sprocysts - redia - many cercariae (snail).Cercariae emerge from the snail and reach water.Development in the second intermediate host (crab or crayfish)Cercaria (invade the crayfish or crabs) -

15、mertacercaria.cercariaeDevelopment in final host (human)Humans are infected by ingesting uncooked crabs or crayfish containing metacercariae.The metacercariae excyst (脫囊) in the duodenum and penetrate the intestinal wall and go into the abdominal cavity.The larvae migrate around or through the diaph

16、ragm (膈肌) into the pleural cavity （胸腔） and lungs.The larvae mature to adults in the vicinity of the bronchi, where they discharge (release) eggs into the bronchial secretions (sputum).The eggs are coughed up and spat out or swallowed and passed in the stool.The larvae also migrate to other organs, s

17、uch as liver, kidney, brain etc.在人體內(nèi)發(fā)育 囊蚴 童蟲 成蟲（蟹/ 蛄） （小腸-腹腔） （肺） 童蟲/成蟲（rare） （皮下/肌肉/肝）生活史要點(diǎn)外界水體為山間溪流。 第一中間宿主是川卷螺；第二中間宿主是淡水溪蟹及蝲蛄。終末宿主是人，保蟲宿主為犬科及貓科動(dòng)物。人因食入含囊蚴而感染。寄生部位是肺，也可在皮下/腦等處。Pathogenesis and pathological changes The adult worms in the lung lead to an eosinophilic inflammatory reaction and the for

18、mation of 1-2cm fibrous capsule.The capsules surrounds and encloses parasites.The capsule swells and erodes into a bronchiole, resulting in expectoration (sputum) of the brownish eggs, blood, and an inflammatory exudates. A section of infected lung. There is a transect of adult in fibrous capsule .T

19、here are many fibrous capsule in lungs. Maybe there adults in it.致病 PATHOGENESIS-病理變化 以肺型為例 膿腫期：組織壞死/出血/炎性滲出物， 周圍肉芽增生形成膿腫壁，但較薄。囊腫期：膿腫內(nèi)有醬色粘稠的膿液，周圍纖維組織增生形成囊腫。瘢痕期：蟲體死亡/游走他處，囊腫與支氣管相通，排出內(nèi)容物/吸收，肉芽填充囊腔，發(fā)生纖維化，形成瘢痕。Clinical featuresThe acute phase (invasion and migration) may be marked by diarrhea, abdominal

20、 pain, fever, cough, urticaria, hepatosplenomegaly, pulmonary abnormalities, and eosinophilia（嗜酸性粒細(xì)胞增多）. During the chronic phase, pulmonary manifestations include cough, expectoration of discolored sputum, hemoptysis (咳血）.Extrapulmonary locations of the adult worms result in more severe manifestati

21、ons, especially when the brain is involved. (epilepsy, paralysis, homonymous hemianopsia(偏盲）, optic atrophy（萎縮）, and papilledema )Sometimes, encysted worms may be found in the abdominal wall, lymph nodes, heart and so on.Introduction to some symptomsEpilepsy （癲癇） : A disorder of brain function chara

22、cterized by recurrent seizures（周期性發(fā)作） that have a sudden onset. At the set, the patient falls to ground unconscious with his muscles in a state of spasm.Paralysis （偏癱） : Muscle weakness that varies in its extent, it severity, and the degree of spasticity (contraction) or flaccidity (weakness) accord

23、ing to the nature of the underlying disease and its distribution in brain, spinal cord, peripheral nerves, or muscles.Hemianopsia （偏盲） : Absence of half of the normal field of vision.Optic atrophy （視神經(jīng)萎縮） : Degeneration of the optic nerve. It may be secondary to disease within the eye or it may foll

24、ow damage to the nerve itself resulting from injury or inflammation.Papilledema （視神經(jīng)乳頭水腫） : Swelling of the first part of the optic nerve (the optic disc or optic papilla).臨床分型及表現(xiàn)胸肺型：最多見，可有發(fā)熱、胸痛、 痰、胸水等表現(xiàn)。腦型：危害較大，可有頭痛、癲癇 癱瘓等表現(xiàn)。皮膚型：游走性皮下包塊。腹型：有腹痛、腹瀉等表現(xiàn)。亞臨床型：無癥狀，但多項(xiàng)免疫學(xué)（+） Laboratory Diagnosis Diagnosis is based on microscopic demonstration of eggs in stool or sputum, but these are not present until 2 to 3 months