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1、 吸虫 Trematodes (Flukes)自学内容华支睾吸虫(考试范围)布氏姜片吸虫(考试范围) 卫氏并殖吸虫(考试范围)日本血吸虫(考试范围重点)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 (皮层) and an inner layer of muscle cells. The cuticle is cellular (syncytium,合体细胞).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 (输出管) / 1 vas deferens (输精管) The female reproductive system: 1 ovary / 1 oviduct (输卵管) / 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卫氏肺吸虫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(卵黄腺) are extensive in the lateral fields.Morphology - EggThey are yellow-brown, ovoid. 80118umX4860umA fertilized ovum and about tens yelk-cells
13、(卵黄细胞) 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 (脱囊) 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.在人体内发育 囊蚴 童虫 成虫(蟹/ 蛄) (小肠-腹腔) (肺) 童虫/成虫(rare) (皮下/肌肉/肝)生活史要点外界水体为山间溪流。 第一中间宿主是川卷螺;第二中间宿主是淡水溪蟹及蝲蛄。终末宿主是人,保虫宿主为犬科及猫科动物。人因食入含囊蚴而感染。寄生部位是肺,也可在皮下/脑等处。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-病理变化 以肺型为例 脓肿期:组织坏死/出血/炎性渗出物, 周围肉芽增生形成脓肿壁,但较薄。囊肿期:脓肿内有酱色粘稠的脓液,周围纤维组织增生形成囊肿。瘢痕期:虫体死亡/游走他处,囊肿与支气管相通,排出内容物/吸收,肉芽填充囊腔,发生纤维化,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(嗜酸性粒细胞增多). 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(萎缩), and papilledema )Sometimes, encysted worms may be found in the abdominal wall, lymph nodes, heart and so on.Introduction to some symptomsEpilepsy (癫痫) : A disorder of brain function chara
22、cterized by recurrent seizures(周期性发作) that have a sudden onset. At the set, the patient falls to ground unconscious with his muscles in a state of spasm.Paralysis (偏瘫) : 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 (视神经萎缩) : 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 (视神经乳头水肿) : Swelling of the first part of the optic nerve (the optic disc or optic papilla).临床分型及表现胸肺型:最多见,可有发热、胸痛、 痰、胸水等表现。脑型:危害较大,可有头痛、癫痫 瘫痪等表现。皮肤型:游走性皮下包块。腹型:有腹痛、腹泻等表现。亚临床型:无症状,但多项免疫学(+) Laboratory Diagnosis Diagnosis is based on microscopic demonstration of eggs in stool or sputum, but these are not present until 2 to 3 months
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