医学寄生虫学：卫氏并殖吸虫

1、卫氏并殖吸虫 Paragonimus westermaniBrief introductionCause of paragonimiasis, in carnivores, First known in 1878Subacute to chronic inflammatory disease of the lung.Paragonimiasis : zoonosisMorphologyAdult worm（1）Thick, reddish brown and ovoid (2) 10mm5mm 4mm (3) oral and ventral suckers : equal in size (

2、4) two testes , present side-by-side at the posterior fourth of the body. (5) ovary: 5-6 lobes uterus (6) vitelline follicles卵黄腺 Live adultMorphologyEgg100m55m golden brownasymmetrically ovoida thick and asymmetric shell with a distinct operculum. 1 ovum (卵细胞 ) more than 10 vitelline cells(卵黄细胞) Lif

3、e cycle Adult （Lungs of humans or animals） EggsMiracidiumSporocyst Redia (two generations)Cercaria Meta- cercariaCrustaceans including crabs, cray-fishes (溪蟹、蝲蛄)淡水螺A Cross-section of Paragonimus Sp in LungsMelania (川卷螺）Fresh water snail: Semisulcospira libertina（放逸短沟蜷） 蜷科(Thiaridae) and 黑贝科(Pleuroce

4、ridae)The first intermediate hostThe second intermediate host Fresh water Crab Fresh water crayfish=crawdad (Cambaroides spp)溪蟹Human Carnivores: dog, cat, tiger, leopardDefinitive hostMetacercariae 囊蚴Spherical , 300400 m, Two layers of transparent walls.Key points of life cycleSite of inhabitation:

5、lungs Infective stage: metacercariaInfective mode: ingestion of crabs and crayfish with metacercariaeIntermediate hosts: 1st int. host : Melania snail(川卷螺); 2nd int. host: crab and crayfish(溪蟹、蝲蛄)Reservoir hosts: tiger, lion, wolf, fox, dog, leopard, cat Paratenic host: boar(wild pig)Life span: 4-5

6、yearsPathogenesis Acute infection: induced by larval invasion and migration ( intestine, liver and lung)Chronic infection: abscess, cyst, fibro-scar1.Abscess stage脓肿期2.Cystic stage囊肿期3.Fibrous scar stage纤维疤痕期Allergic reaction: fever, urticaria (荨麻疹), IgEPathogenesisEncapsulated cyst in lungCross sec

7、tion of lung from patient infected with P. westermani囊肿期Migration 肠 -腹腔-胸腔-肺腹壁-皮下-肠系膜（肝）纵膈-破裂孔-脑Manifestations of paragonimiasisAsymptomatic paragonimiasisThorax lung paragonimiasis: 胸肺型 resemble pulmonary tuberculosis(结核)Cerebral paragonimiasis:脑脊髓型 resembles cerebral cysticercosis(脑囊虫病). epilepsy(

8、癫痫), hemiplegia(偏瘫), monoplegia(单瘫),aphasia(失语), visual disturbanceAbdominal paragonimiasis:腹型abdominal pain，diarrhea or dysentery with blood, mucus and eggs in feces. Subcutaneous paragonimiasis:皮下包块型 wandering and painless subcutaneous nodules. Thorax lung paragonimiasis 胸肺型low fever, loss of appe

9、tite, night sweating, chest pain, loss of weight, chronic cough and rusty-brown sputum Cerebral paragonimiasis 脑脊髓型headachefeverNauseavisual disturbances convulsive seizuresHand distortioncystsSubcutaneous paragonimiasis皮下包块型DiagnosisHistoryParasitological examination : sputum & feces Immunodiagnost

10、ic test: IDT皮内试验 ELISA for special antibodies dot-ELISA X-ray /CT Eosinophilia 80Far East, Africa and South AmericaWorld wide distribution Epidemiologycrayfish endemic area蝲蛄流行区crab endemic area溪蟹流行区EpidemiologyIn China :23 provinces and autonomous regions.EpidemiologyDefinitive hosts: humans; Reser

11、voir host： tiger, dog, cat Paratenic host: boar(wild pig)Zoonosis（人兽共患病）First intermediate hosts; Second intermediate hostsRoutes of infection : 1) raw crab or crayfish containing metacercariae 2)meat of a paratenic host containing immature flukes3) water containing metacercariae囊蚴 or cercariae尾蚴Res

12、ervoir hostsome endemic: dogs, catssome endemic: wild animalsDrunk crabMontanic rivuletEpidemiologyPrevention and controlHealth education : eating habitsUse of molluscacides灭螺剂Chemotherapy Praziquantel：75mg/(kg/d) 2天Bithionol(硫双二氯酚） Pagumogonimus skrjabini 斯氏狸殖吸虫Cutaneous paragonimiasisLife cycle re

13、sembles that of P. westermaniDefinitive hosts: Paguma(果子狸), cats, dogs etcHuman: non-normal hostMost of larvae cant develop to mature wormMigration of larvae cause pathological changesImmunological test & biopsyP. weatermaniP. SkrjabiniDHHUMAN and animalswild animals1stIHSemisulvospira libertinaTric

14、ula humida (拟钉螺）2ndIHCrabscrayfishescertain crabs (石蟹）PathogenesisLung/Cerebral/liver paragonimiasis,Subcutaneous or visceral larva migransDiagnosiseggs,immunological detection; biopsyimmunological detection; biopsyP. westermaniC. sinesis F. buskiDefinitive hosthumanhumanhumanReservoir hostTiger, dog .Dog, catpigParatenic hostBoarnonoeggSputum/feces Feces FecesMiracidium Water Snail Water