人体寄生虫学：2-线虫概述及钩虫

1、线虫概述及钩虫INTRODUCTION TO NEMATODE AND HOOKWORM线虫概述 线虫成虫形态特征 线虫生活史特征 钩虫 形态/生活史 致病/诊断 防治原则讲 授 内 容 熟悉线虫的结构和形态特点； 掌握与钩虫致病和/或诊断有关的成虫、虫卵形态特点、生活史要点； 熟悉钩虫的致病及实验诊断； 了解钩虫的流行及防治原则。学 习 要 求自 学 内 容似蚓蛔线虫 （考试范围）毛首鞭形线虫（考试范围）蠕形住肠线虫（考试范围）旋毛形线虫 （考试范围）结膜吸吮线虫（非考试范围）丝虫 （非考试范围） 线状圆柱形，雌雄异体，雌大雄小，雄虫尾端卷曲或膨大，雌虫尾端尖直或钝圆。 多无固着器官。 消化

2、器官较完整，具有口、咽、食道、肠及肛门。 雄虫生殖器官呈单管型，雌虫多呈双管型。 具有原（假）体腔，体壁由外向内依次为角质层、皮下层及肌层。线虫成虫的形态特征线状圆柱形，雌雄异体，雌大雄小，雄虫尾端卷曲或膨大，雌虫尾端尖直或钝圆。线虫多无固着器官（吸虫有口/腹吸盘，绦虫有吸盘和/或小钩）雄虫生殖器官呈单管型，雌虫多呈双管型线 虫 生 活 史 特 征线虫生活史中有虫卵、幼虫和成虫三期，由幼虫发育为成虫需蜕皮四次。 线虫多为土源性蠕虫（不需中间宿主），少数为生物源性蠕虫（需中间宿主）。根据寄生部位可将线虫分为肠道（消化道）线虫与组织内线虫。 钩 虫 HookwormsINTRODUCTIONThe

3、 term hookworm refers to two organisms, Ancylostoma duodenale (A. duodenale 十二指肠钩口线虫，十二指肠钩虫) and Necator americanus (N. americanus 美州板口线虫，美洲钩虫). Some differences between two adult hookworms. The egg, larvae and life cycle are very similar.Distinct geographic distribution.N. americanus is found in No

4、rth and South america, China, India, and Africa.A. duodenale is seen in the Mediterranean basin, the Middle East, northern American, India, China, and Japan.Morphology Adult Adults of both species are pinkish-white. The females average females measure about 9 to 12mm in length. Males are typical sma

5、ller, ranging from 5 to 10mm. The males are equipped with a prominent posterior copulatory bursa （交合伞）. The heads of both species are often curved dorsally, giving these worms the hooked appearance . Their common name, hookworm, is derive from their morphological characteristic.鉴别点 十二指肠钩虫 美洲钩虫体形 头尾均

6、背曲，呈“C”型 头背曲，尾腹曲，呈“S”型The mouth capsule（口囊） of N. Americanus contains a pair of cutting plates（板齿）. The mouth capsule of A. duodenale contains two pairs of hooked teeth（钩齿）. 鉴别点 十二指肠钩虫 美洲钩虫口囊 腹侧前缘有两对钩齿 腹侧前缘有一对板齿 背肋 （Dorsal ray） 远端分叉，二分三歧 基部分叉，二分二歧 交合刺 (Copulatory spicule) 二刺平行伸出，末端永不相交 二刺平行伸出，末端形成小钩

7、鉴别点寄生人体的两种钩虫成虫鉴别 鉴别点 十二指肠钩虫 美洲钩虫大小(mm) 8130.40.6 7110.30.4体形 头尾均背曲，呈“C”型 头背曲，尾腹曲，呈“S”型口囊 腹侧前缘有两对钩齿 腹侧前缘有一对板齿背肋 远端分叉，二分三歧 基部分叉，二分二歧 交合刺 两根末端分开，不相交 一根末端呈倒钩，与另一根合并雌虫尾刺 有 无Morphology - Egg Ovoid in shape and average 60um in length, 40um in width. A thin, clear and colorless egg-shell. The eggs are in th

8、e early cleavage stage when passed in the stool. They have a clear space between the developing embryo （胚胎期幼虫）and the thin eggshell（卵壳）. Life cycleDevelopment of eggs in soilInfective stageFilariform（丝状蚴）For 1w in moist, warm soilDevelopment of hookworm in human bodyFilariforms（丝状蚴） penetrate skinMi

9、grate via bloodstream Heart Lung Alveoli of lungs （肺泡） Bronchi(支气管) Trachea(气管) pharynx(咽) (Swallowed)Larvae mature and mate in intestineEggs in fecesCharacteristics of life cycleHuman is the only host (direct life-cycle).The location of adult: Small intestine.Infective stage: Filariform （丝状蚴）.Nutri

10、tion: Blood.The infecting style （感染方式） : Skin （avenues of invasion）.Larvae migration in body: Heart , lung (circulatory system); alveoli, bronchi, trachea, pharynx (respiratory system); esophagus, stomach, small intestine (digestive system).The parasitizing style (寄生方式): Attaching and biting to the

11、mucosa （咬附或钩附）。PathogenesisThe host immune response (larvae).Effects of larval migration (larvae).Mechanical effects of the adults (necrosis of the intestinal within the adult worm mouth).Anemia.AnemiaBlood loss by direct ingestion of blood by the worms. Continued blood loss from the original attach

12、ment site (the worm secreted anticoagulant，抗凝素).Iron deficiency caused the lower hemopoiesis.Clinical features Both migrating larvae and adult worms of hookworms can cause pathological changes and symptoms.Damage of larval penetration of skinDamage of migrating larvaeDamage of adult wormsDamage of l

13、arval penetration of skinThe larval penetration of skin causes dermatitis（皮炎）.A small lesion with an itching (痒) and burning sensations (烧灼感) produced at the site of penetration.Scratching (刮痕) usually leads to infection by bacteria.Damage of migrating larvaeBronchial asthma（支气管哮喘）Transient eosinoph

14、ilia Angioneurotic edema（血管神经性水肿）Pneumonitis（肺炎）Bronchospasm（支气管痉挛）a dry or productive cough, wheezing , fever.Damage of adult worms If the worm burden is small, infections with worms may be asymptomatic. Clinical manifestations may result from a heavier worm load（虫荷） in the intestinal lumen. (It is

15、 similar to damage of migrating larvae )Gastrointestinal symptoms（消化道症状）Iron deficiency anemia（缺铁性贫血） Gastrointestinal symptomsFatigue（乏力）, nausea（恶心）, vomiting（呕吐）, abdominal pain, diarrhea（腹泻） with black to red stools, weakness（虚弱）, and pallor（苍白）.Hookworm, section of a worm attached to the mucosa

16、 Iron deficiency anemiaIn chronic infection, the main symptom is iron deficiency anemia (microcytic小细胞的, hypochromic低色素的) with pallor, edema of the face and feet, listlessness（萎靡）, and hemoglobin levels of 5 g/dl or less.There may be cardiomegaly（心脏肥大） and both mental and physical retardation（发育迟缓）.Laboratory DiagnosisMicroscopic identification of eggs collected in stool is the method of choice. The eggs are best seen in the direct smear（粪便直接涂片） or brine floatation（生理盐水浮聚法）.The larvae may be cultivated by fecal cultu