人體寄生蟲學課件：Filaria (絲 蟲)

1、 Filaria (絲 蟲)Introduction The adult is slender just like the thread.Special: tissue-dwelling (not in digestive tract), transmitted by blood-sucking insecta.Filariasis (絲蟲病) one of the five major parasitic diseases in Chinaone of the six major tropic diseases defined by WHOThere are 8 species of fil

2、ariae parasitizing human. Wuchereria bancrofti (班氏吳策線蟲，班氏絲蟲) Brugia malayi (馬來布魯線蟲，馬來絲蟲) 1. adultsamewhitesmooththread-like, female 510 cm, male 2.54 cmmouth on the top, with papillae (乳突) around ituterus with eggs and larvae. Ovoviviparity (卵胎生)I. Morphology2. Microfilaria (微絲蚴)slender, the head bl

3、unt, the tail sharpsheath (鞘膜)body nuclei (體核) caudal nuclei (尾核)cephalic space (頭間隙)nerve ring, at the anterior 1/5 part of the bodyBancroftian microfilaria: body nuclei equal in sized, clearly, defined, countable without caudal nucleus.anterior and posterior part of bancroftian microfilaria Microf

4、ilaria of B. malayi: the body nuclei is unequal sized, coalescing,uncountable. The cephalic space is longer with two caudal nuclei.Microfilaria of B. malayiW. bancroftiB. malayiappearancesoftstiffsizelarger2442967 msmaller1772306 mcephalic space(length : width)shorter1:1longer2:1 body nucleiline up

5、in ordercountableoverlapdifficult to distinguishcaudal nucleinoyes (two)3. Filariform larva (絲狀蚴)slenderthread-like, for W. bancrofti 1.6 mm, for B. malayi 1.3 mmintact digestive tractactiveII. Life CycleII. Life Cycle1. Biohelminth (生物源性蠕蟲)2. Intermediate host: mosquito3. Definite host: human4. Inf

6、ective stage: filariform larva5. Infective route: bitten by mosquito6. Site of inhabitation: lymphatic tissue7. Pathogenic stage: adult and larva1. Adults live in a coiled mass in lymphatic system of humans - generally in the lower parts of the body. W. bancrofti : superficial and deep lymphatic sys

7、tem B. malayi : only in superficial lymphatic system2. Females produce thousands of microfilariae that are released into the lymph and move into peripheral blood.3. Microfilariae are ingested when night-biting mosquito takes blood meal.4. Microfilariae migrate to the mosquito muscles and molt to sau

8、sage-shaped larva.5. L3 migrate to the mouth parts of the mosquito and enter human skin when the mosquito bites.L3 is infective stage to human.6. L3 enter small lymphatic vessels and move to the large lymphatic vessels - molt 2x to become adults adults take 3 mon1 year to mature and produce microfil

9、ariae.7. Life span: for adults 410 years for microfilaria 23 months Nocturnal periodicity (夜現(xiàn)周期性)During the day time, the microfilariae residue in capillaries of lung. Then at night time, the microfilariae appear in the peripheral blood. The number of microfilariae in the peripheral blood is low dur

10、ing day time and increases at night.W. bancrofti : 10 p.m. to 2 a.m. B. malayi : 8 p.m. to 4 a.m. Why? human: rhythm, vagus nerve (迷走神經(jīng)), capillaries, intake of oxygen, etc. microfilaria Microfilariae of Wuchereria bancroftiIII. PathogenesisFilariform larva, adult and microfilaria are pathogenic.Inf

11、luencing factor:speciesintensitysiteimmunitysecondary infection1. Acute stage:allergic reactionlymphangitis (淋巴管炎), lymphadenitis (淋巴結炎)orchitis (睪丸炎) and inflammation of spermatic cord (精索) are only found in W. bancroftifilarial fever (絲蟲熱).Adults occur in the lymphatic vesselserysipelas-like derma

12、titis (丹毒樣皮炎)red swelling of the skinpressing painburning sensationerysipelas-like diseases (流火)a red lineadterminal (離心的)2. Chronic stage:（1）Elephantiasis (象皮腫)：most frequent signs of late filariasisoften occur in lower limb and scrotum (陰囊)pitting edema (凹陷性水腫) to non-pitting edemasecondary infect

13、ionmicrofilaria usually absent in the peripheral blood.Elephantiasis due to Brugia malayi. Pitting does not occur in this stage (solid edema). Elephantiasis due to Brugia malayi, accompanied by severe dermatitis and secondary bacterial infection.elephantiasis of breasts and upper limbelephantiasis o

14、f the vulva (外陰)elephantiasis of the scrotum (陰囊)（2）Hydrocele of testis (睪丸鞘膜積液)lymph nodes in spermatic cord and testisonly occur when infected by W. bancrofti（3）Chyluria (乳糜尿)preaortic lymph nodes (主動脈前淋巴結) and major lymph nodes of intestine (腸干淋巴結)only occur when infected by W. bancroftichyluria3

15、. Microfilaremia (微絲蚴血癥): carrier4. Tropical pulmonary eosinophilia (熱帶肺嗜酸粒細胞增多癥, inapparent filariasis)：microfilaria in lung and lymph nodeseosinophilia(嗜酸性粒細胞增多), low-grade fever, cough in night, etc.IV. Diagnosissymptoms, signs and history of living in endemic areas-indicativeThe final diagnosis

16、depends on the etiological examination-microfilariae.First choice: thick blood smear (厚血膜法)take blood at night during 9 p.m. to 2 a.m.fresh blood smear (新鮮血滴法)mass screeningmillipore membrane filtration (微孔濾膜法)concentrationimmunologic testV. Epidemiology1. Distribution: W. bancrofti is world-wide pr

17、evalent especially in Asia and Africa. B. malayi is prevalent in east and south Asia. In China, W. bancrofti distributes in 16 provinces on the south of Yellow River, while B. malayi presents in 13 provinces on the south of Yellow River.B. malayi is absent in Shandong, Hainan and Taiwan.W. bancrofti

18、B. malayi2. Source of infectionthe patient and the carriers with microfilariae in their blood.3. Vectorfor W. bancrofti: Culex pipiens pallens (淡色庫蚊) C. fatiga (致倦庫蚊)for B. malayi: Anopheles sinensis (中華按蚊) Anopheles anthropophagus (嗜人按蚊)4. Susceptible population: all people5. Reservoir hostW. bancr

19、ofti: no reservoir hostB. malayi: cat, monkey, pangolin (穿山甲), etc. VI. Treatment and Prevention1. First choice drug is diethylcarbamazine (DEC, 海群生).It can kill the microfilariae and adults of filariae. The standard dose is 6 mg/kg, given after each meal, over a period of 10-14 days. Initially lowe

20、r dose (1-3 mg/kg) once a day should be started in order to decrease side effects of the drug in cases of heavy parasitic load. Side effects of the drug include fever, headache and muscle pains, vomiting, weakness; usually result from rapid destruction of microfilariae and adult worms, especially in

21、 heavily infected individuals.DEC table salt (3:1000) are used in endemic areas. People take this salt over 6 months, result in an elimination or great reduction of microfilariae in the blood stream.ivermectin (伊維菌素), furapyrimidone (呋喃嘧酮)2. Symptomatic therapy (對癥治療)Pressure bandages on enlarged li

22、mbs forces lymph out.Remove the giant elephantiasis of the scrotum, chest and limbs if muscle involvement is minimal.For chyluria, kidney pelvis douching therapy (腎盂沖洗), surgery.Prevention & controlRegular Screening Mass treatmentMosquito control. Eradicate mosquito breeding places and control mosqu

23、itoes. It is important to protect people from mosquito bite. Classification by the parasitic sites:1) live in lymphatic system： Wuchereria bancrofti（班氏吳策線蟲, 班氏絲蟲） Brugia malayi（馬來布魯線蟲, 馬來絲蟲） Brugia timori （帝汶絲蟲）2) Live subcutaneously： Loa loa（羅阿絲蟲） Onchocerca volvulus（ 盤尾絲蟲） Dipetalonema streptocerc

24、a（ 鏈尾絲蟲） 3) live in body cavity： Dipetalonema perstans ( ?，F(xiàn)絲蟲) Mansonella ozzardi（歐氏絲蟲） The common filarial parasites of humandistributionvectorParasitic sitepathogenesisWuchereria bancroftiWorldwidemosquitolymphatic tissuelymphatic damageBrugia malayiAsian mosquitolymphatic tissuelymphatic damageBr

25、ugia timoriAfricamosquitolymphatic tissuelymphatic damageOnchocerca volvulusAfricasandfly (蚋)subcutaneousriver blindnessLoa LoaAfricagadfly (虻)subcutaneoussubcutaneous lumpDipetalonella perstansAfricaMidge (蠓)subcutaneousnonpathogenicDipetalonema streptocercaMiddle and south AmericaMidge (蠓)thoracic

26、 cavity abdominal cavitynonpathogenicMansonella ozzardiMiddle and south AmericaMidge (蠓)abdominal cavitynonpathogenicTrichinella spiralis(旋毛形線蟲)Department of ParasitologyYang qingIntroductionLife cycle is special.The adult and the larva live in the same host but it has to change a host to complete t

27、he life cycle.Trichinosis (旋毛蟲病) zoonosis (人畜共患病)Human get infection resulting from eating raw meat.I. Morphology1. Adultjust like the white threadsmallfemal: 34 mm, male: 1.41.6 mm in lengthpharyngeal tube is long with stichosome (桿狀體) on the back of the posterior partstichosome (桿狀體): about 50 sti

28、chocytes (桿細胞), bead-like, single layer, secret agents for digestion and with strong antigenicityBoth the male and female adults have one set of reproductive organ.ovoviviparity (卵胎生)2. Larvaaverage 1246 m (new-born)parasitizes in skeletal muscle cells (1mm in length)cyst, 0.25-0.50.21-0.42mm in siz

29、e, two layers of cyst wall, usually contains 12 larvae. muscle pellet method (肌肉壓片法)muscle sectioning method (肌肉切片法)II. Life cycleII. Life cycle 1. Infective stage: larvae in cysts 2. Site of inhabitation: adults in small intestine (mainly in duodenum and jejunum) larvae in striated muscle 3. Route

30、of infection: by mouth 4. Life span of the female: 1-2 months 5. Final host and intermediate host: human 6. Reservoir host: pigs, cats, dogs, mice, horse, etc.larvae in raw meat- duodenum- larvae free from the cysts- death adults- goes deep into the mucosa-larvae- vessles-liver-right heart-lung-left

31、 heart-encystation in skeletal muscles all over the bodyswallowed by man digestive juicepenetrate into intestinal wall, develop and molt 4 timesreturn to the intestinal lumenfalling with mucosaIII. PathogenesisThe process of the pathogenesis is divided into 3 stages:1. Invading stage (about 1 week):

32、 also called intestinal stage.The excysted larvae invade the intestinal mucosa where they grow into adults.This process causes intestinal bleeding, edema, ulcers.The patients: abdominal pain, nausea (惡心), anorexia (厭食), vomiting, diarrhea and fever.2. Larva migrating stage (2 weeks-2 months): also called muscle stage.The newborn larvae in the intestinal mucosa penetrate into the circulation system and are carried to all parts of the body. Larval migration hurts vessels and skeletal muscle cells causing local and systemic reactions.The patient: myositis (肌炎) and vasculitis (血管炎). muscula