Trematodes of Small Animals Section One Introduction Chapter Nine Trematodes of Small Animals Section One Introduction

Structure, Functions and Basic Life Cycles of Trematodes 吸虫的结构、功能及基本生活史 Trmatodes of veterinary significance are within the Order Digenea (复殖目) The Structure of Digenetic Trematodes (复殖吸虫的结构)

The adult digenetic trematodes (复殖吸虫) are commonly called ‘flukes (吸虫)’, and occur primarily in the bile ducts (胆管), alimentary tract (消化道) and vascular system (血管系统) Most flukes are flattened dorsoventrally (大多数吸虫背腹扁平)

The oral sucker at the anterior end surrounds the mouth and the ventral sucker is on the ventral surface. The body surface is a tegument (体壁, 体被) which is absorptive and is often covered with spines (棘). The muscles lie immediately below the tegument. There is no body cavity (无体腔) and the organs are packed in a parenchyma (实质)

生殖孔 咽 子宫 雄茎囊 输精管 卵模 卵黄管 睾丸 卵黄腺 盲肠

The Excretory System 排泄系统 The excretory system consists of a large number of ciliated flame cells (有纤毛的焰细胞), which impel waste metabolic products along a system of tubules (小管系统) to the exterior (外界).

The Nervous System神经系统 The nervous system is simple, consisting of a pair of longitudinal trunks (一对纵向神经干) connecting anteriorly with two ganglia (神经节). (Pp. 29 of the Chinese edition)

The trematodes are usually hermaphrodite (雌雄同体) and both cross- and self-fertilization (异体及自体受精) may occur

《小动物寄生虫病学》期中作业题 2004级动物医学专业(小动物疾病防治方向) 姓名： 学号： 1. 简述动物寄生虫病的诊断方法 (70分)。 2. 试述动物寄生虫病的防制原则 (30分)。 11月10日前发致: xingquanzh@scau.edu.cn 13380055552 85283730

The Life Cycle of Digenetic Trematodes (复殖吸虫的生活史) Needs one to two intermediate hosts: The first one: snails (螺); the second one: fish or arthropods (鱼或节肢动物)

Stages of Life Cycle (生活史各期) 卵 (egg)、毛蚴(miracidium)、胞蚴(sporocyst), 雷蚴 (redia), 尾蚴 (cercaria), 囊蚴 (metacercaria)、成虫 (adult) In the final host: 卵 (egg)、成虫 (adult)

In the environment: egg, 毛蚴(miracidium)、尾蚴 (cercaria)、囊蚴 (metacercaria) In the first intermediate host: 胞蚴(sporocyst), 雷蚴 (redia) In the second intermediate host: 尾蚴 (cercaria)、囊蚴 (metacercaria)

Classification of Trematodes (吸虫的分类) Monogenea (单殖目) Aspidogastrea (盾腹目) Digenea (复殖目)

Digenea (复殖目) Family Schistosomatidae (分体科) Family Opisthorchiidae (后睾科) Family Echinostomatidae (棘口科) Family Paragonimidae (片形科)

Section Two Trematodes of the Liver 一、中华枝睾吸虫病(Clonorchiasis) 俗称肝吸虫病，是由后睾科枝睾属的中华枝睾吸虫（Clonorchis sinensis）寄生于犬、猫、猪、鼬、貂等动物及人胆管内所引起的一种吸虫病。 可使肝脏肿大并导致其他肝病变，是一种重要的人畜共患寄生虫病，呈地方性流行，在东南亚国家常见。

（一）Morphology of the trematode 本虫外形似葵花子、扁平、透明，前端稍尖，后端较钝，体表光滑

（二）Life Cycle Requires two intermediate hosts, the first being water snails (淡水螺：纹沼螺，长角涵螺及赤豆螺 ) and the second a wide variety of fish and shrimp (虾), in which the metacercariae are encysted. The final hosts are fish-eating mammals in which they inhabit the bile ducts.

（三）流行病学 普遍流行于日本、韩国、朝鲜、越南、印度及菲律宾等地。主要分布于东亚和东南亚地区，全世界近3,500万人感染。 我国目前感染人数为约1,500万，分布于25个省市 ，其中，广东、广西和海南为重疫区。

猫、狗活动范围广、嗜食生鱼使感染率高达70％80％。 我国淡水产品中的华枝睾吸虫囊蚴的带虫率在60％左右（上海河虾的阳性率曾为71.4％），而且囊蚴极耐干燥及盐腌。

（四）致病作用 虫体寄生于动物的胆管和胆囊内，因机械性刺激，引起胆管和胆囊发炎，管壁增厚，导致消化功能紊乱。 虫体分泌毒素，引起贫血、消瘦和水肿。大量寄生时，虫体阻塞胆管，使胆汁分泌障碍，胆汁在体内集聚形成黄疸现象。

肝脏切面的华支睾吸虫

虫体长期寄生后，刺激肝脏胆管，可使肝脏结缔组织增生，肝细胞变性、萎缩，毛细胆管栓塞， 引起肝硬化，可并发胆囊炎、胆管炎、胆汁性肝硬化以及胆管上皮癌或原发性肝癌

（五）病理变化 猫和狗的主要病变在肝和胆。胆囊肿大，胆管变粗，胆汁浓稠，呈草绿色。 胆管和胆囊内有许多虫体和虫卵。肝表面结缔组织增生，有时引起肝硬化或脂肪变性。除腹腔外，还伴有全身组织和其它体腔积液。

（六）症状 患病猫、犬临床症状多呈慢性经过，临床上可见到动物精神沉郁，病初食欲逐渐减少甚至厌食。 继之呕吐、腹泻、脱水，可视黏膜及皮肤发黄，尿液呈桔黄色，肝区触诊疼痛。 严重感染时长期顽固性下痢，最后出现贫血、消瘦、腹水，多并发其它疾病而死亡。

Diagnosis 1. Clinical signs: 若在流行地区，猫狗常吃生鱼虾，如临床上出现消化不良和下痢等症状，即可怀疑为本病， 2. 粪便中检到虫卵即可确诊。检查方法以浮卵法为佳，离心浮卵法检出率最高。 3. 免疫学方法：IHA and ELISA

Egg of Clonorchis sinesis

Treatment Praziquantel，丙酸哌嗪，Albendazole，六氯对二甲苯，硫双二氯酚，硝氯酚

Control 在流行地区的猪、犬和猫均须进行全面的检查和驱虫。 在疫区禁止以生的或未煮熟的鱼、虾喂养动物。 抓好动物的粪便管理，防止粪便污染水塘。禁止在鱼塘边盖猪舍或厕所。消灭第一中间宿主淡水螺，宜采用捕捉或掩埋的方法、或化学杀螺的方法。

二、后睾吸虫病 后睾吸虫病是由后睾科（Opisthorchiidae）后睾属（Opisthorchis）猫后睾吸虫（Opisthorchis felineus）和麝猫后睾吸虫（O. viverrini）寄生于犬、猫、狐等动物的肝胆管中引起的，偶见于胰管和小肠，多呈地方性流行，对犬猫危害较大。

（一）病原形态 猫后睾吸虫虫体形状似华枝睾吸虫，但略小。 麝猫后睾吸虫成虫和虫卵的形态与华枝睾吸虫相似。 So, may need to differentiate these three species

（二）生活史 Similar to that of Clonorchis sinensis First intermediate host: 李氏豆螺（Bithynia leachii） Second intermediate host: fish of various species

（三）流行病学 猫后睾吸虫的终宿主非常广泛，除犬、猫外、狐、獾、貂、水獭、海豹、狮、猪及人等均可感染，成为保虫宿主。 虫卵在水中存活时间较长，平均温度为19℃时可存活70天以上。

（三）流行病学 第一中间宿主淡水螺的分布较广泛，几乎各种池塘均可发现。第二中间宿主淡水鱼有数十种。 本病流行广泛。有的地区猫的感染率可高达100％，犬的感染率为90％，感染强度可达5000多条。

（四）致病作用和症状 （五）诊断 Similar to that of infection with Clonorchis sinensis

（六）Treatment and control Similar to that of infection with Clonorchis sinensis

Section Three Trematodes of the intestines (肠吸虫病(棘口吸虫病) 犬猫肠吸虫病是由棘口科外隙属（Echinochasmu）和棘口属（Echinostoma）中的多种吸虫寄生于犬、猫的肠道内所引起的。 该病在我国江苏、浙江、福建、广东、广西、云南、四川以及天津等地广泛流行，对犬、猫造成一定危害。

All have head and body spines (棘)! 犬外隙吸虫（Episthmium canium): small, 1-1.5 mm) 日本棘隙吸虫（Echinochasmus japonicus): small, 0.66-1.04mm) 园圃棘口吸虫（Echinostoma hortense): large, 8-9.2mm) All have head and body spines (棘)!

Life cycles, epidemiology, pathogenesis, diagnosis, treatment and control are similar to that of other trematodes

Section Four Trematodes of the Lungs 一、卫氏并殖吸虫病 卫氏并殖吸虫病是由卫氏并殖吸虫（Paragonimus weseermani）寄生于肺脏所引起的一种重要的人兽共患寄生虫病。主要感染犬、猫、人。

（一）Morphology of the Pathogens 成虫体肥厚，新鲜虫体呈红褐色，半透明，类似半瓣黄豆状。虫体长712mm，宽46mm，厚3.55mm。体表具有小棘。

（二）Life Cycle 发育过程需要两个中间宿主。第一中间宿主为淡水螺类(川卷螺)，第二中间宿主为淡水蟹或蝲蛄（又名螯虾)。 囊蚴被吃入终宿主体内后，经消化液作用，在小肠内童虫脱囊而出。游离的童虫可穿过肠壁进入腹腔，徘徊于各内脏之间或侵入组织，尤其是肝脏。童虫经过13周窜扰后，再穿过横膈经胸腔而入肺脏。发育为成虫，并成熟产卵。

Life cycle

（三）Epidemiology 传染源是病人和保虫宿主。 卫氏并殖吸虫在我国分布广泛，分布于23个省、市、自治区，以我国的辽宁、吉林、黑龙江、浙江、安徽、福建、河南及四川的流行较为严重。 传染源是病人和保虫宿主。 肺吸虫的第一中间宿主川卷螺类，第二中间宿主甲壳动物淡水蟹类或蝲蛄类常共同栖息于同一自然环境中，有利于生活史的完成。

居民有吃生或半生溪蟹或蝲蛄的习惯，是人体感染的主要因素。

（四）Pathogenesis and pathological changes 主要是由于童虫或成虫在脏器及组织内的移行窜扰、寄居破坏及虫体的代谢产物刺激等因素引起。 成虫在肺部寄生引起组织形成囊状空洞。病理变化的发展过程，大致可分为脓肿期、囊肿期和纤维疤痕期。 因肺吸虫时常停留或移动，故以上三期病变可同时见于同一脏器内，除最常寄生的肺部外，还有脑部等。

（五）Clinical Signs 一般发病缓慢，症状出现最早的在感染后数天至一个月内，多数在36个月不等。 患猫和犬表现精神不佳，咳嗽，早晨较剧烈，初为干咳，以后有痰液，痰多呈白色黏稠状并带有腥味。 铁锈色或棕褐色痰为本病的特征性变化。

（六）Diagnosis 根据流行病学资料，结合是否在本病的流行地区生吃或半熟食石蟹或蝲蛄的历史，结合临床症状和实验室检查等作出诊断。 1．痰液或粪便虫卵检查 2．血清学方法诊断

Treatment and control Similar to that of infection with Clonorchis sinensis

二、斯氏狸殖吸虫病 斯氏狸殖吸虫（Pagumogonimus skrjabini），其幼虫主要寄生于皮下，引起皮下结节的特征病变，又称皮下型并殖吸虫病。 本虫50年代后期，国内首先在四川地区发现，继而又先后在江西、贵州、云南、湖南、湖北、福建、河南、浙江、广西、广东、甘肃等省陆续发现。

成虫虫体狭长，前宽后窄，两端较尖。虫体长11.018.5mm

本虫的生活史与卫氏并殖吸虫相类似。所不同者是本虫的保虫宿主为自然感染的果子狸、犬、猫、豹等。 人为本虫的非正常宿主，人体感染后绝大多数停留在童虫期，少见发育成熟并产卵。

已证实的第一中间宿主有泥泞拟钉螺、微小拟钉螺、中国小豆螺、建瓯拟小豆螺等。 第二中间宿主有锯齿华溪蟹、雅安华溪蟹、河南华溪蟹和僧帽石蟹等。 多种动物，如棘腹蛙、鸟、鸭、鼠等可作为斯氏狸殖吸虫的转续宿主。

Diagnosis: 皮下整块活体组织检查是本病的主要诊断方法 Treatment and Control: 同卫氏并殖吸虫病。

Section Five Trematodes of the Circulation System

血吸虫病患者

毛泽东七律二首　送瘟神　 1958.07.01 绿水青山枉自多，华佗无奈小虫何！千村薜荔人遗矢，万户萧疏鬼唱歌。坐地日行八万里，巡天遥看一千河。牛郎欲问瘟神事，一样悲欢逐逝波。 春风杨柳万千条，六亿神州尽舜尧。红雨随心翻作浪，青山着意化为桥。天连五岭银锄落，地动三河铁臂摇。借问瘟君欲何往，纸船明烛照天烧。

Family Schistosomatidae (分体吸虫科) This family is primarily parasitic in the blood vessels of the alimentary tract and bladder

Hosts: Schistosoma (分体属、血吸虫属) All domestic mammals and humans. Mainly important in cattle and buffalo.

Predilection Site: Intermediate hosts: Usually mesenteric veins (肠系膜静脉); one species occurs in nasal veins Intermediate hosts: Water snails. 湖北钉螺 (Oncomelania hupensis) for S. japonicum

Species and distribution: Major: Schistosoma bovis Ruminants in Africa, Middle East, Asia, southern Europe S. mattheei (梅氏) Ruminants and occasionally man in Africa S. japonicum Man and most domestic animals in the Far East

Minor: S. leiperi Cattle in Africa S. spindale Ruminants, horses and pigs in Asia and the Far East S. incognitum (不明) Pigs and dogs in India and Pakistan S. mansoni (曼氏) Man and wild animals in Africa, South America and the Middle East S. (syn. Orientobilharzia) turkestanica Ruminants in Asia S. nasalis Ruminants and horses in India and Pakistan.

IDENTIFICATION Gross: The sexes are separate, the male is broad and flat and about 2.0cm long. The male carrys the female in the hollow of its inwardly curved body (gynaecophoric canal, 抱雌沟). This characteristic and the vascular predilection site are sufficient for generic identification.

Microscopic: The eggs are 100-500 µm long, spindle-shaped (纺锤体形) and have a lateral or terminal spine (棘). There is no operculum (盖).

Female Schistosoma in the gynaecophoric canal

LIFE CYCLE Females (in the mesenteric vein) produce eggs Eggs with the unhatched miracidia are passed in the faeces The eggs hatch in minutes in water and the miracidia penetrate the snails

Development to the cercaria in the snails (around 5 weeks, without redial and metacercarial phase) Penetration of the final host by the motile cercariae via skin or drinking water Cercariae lose their forked tails and transform to schistosomula (童虫) or young flukes

To the systemic circulation through the heart and lungs Via blood stream To the systemic circulation through the heart and lungs They locate in the portal veins (门静脉) in the liver and become sexually mature before migrating to their final site, the mesenteric veins. The prepatent period is 6-7 weeks.

Pathogensis 1. 机械性损伤：尾蚴钻入宿主皮肤时皮炎，童虫移行的损伤---血管炎 2. 免疫病理反应: 虫卵沉积于肝脏、肠壁等宿主组织可诱导形成抗原-抗体复合物炎症、溃疡形成瘢痕组织钙化肝硬化、腹水

Pathogenesis (continued) 3. 吸血及毒素(代谢产物)作用: 导致宿主精神沉郁、贫血 4. 异位损害 (ectopic lesion): such as adults or eggs in the lungs, or in the brain, these could cause lesions (脑病、肺病症状)

CLINICAL SIGNS These are fever, diarrhoea, sometimes blood stained and containing mucus, anorexia (厌食), thirst (渴感), anaemia (贫血) and emaciation (消瘦). Severely infected cattle and buffalo can die quickly

EPIDEMIOLOGY Schistosoma spp. are totally dependent upon water as a medium for infection of both the intermediate and final host. Percutaneous infection (经皮肤感染) may occur where livestock are obliged to wade in water.

A. The examination of miracidia DIAGNOSIS 1. Clinico-pathological picture of persistent diarrhoea, often blood stained and containing mucus, wasting and anaemia, coupled with a history of access to natural water sources. 2. Parasitological examination: A. The examination of miracidia

C. Postmortem examination: to confirm suspected infection B. The demonstration of the characteristic eggs in the faeces or in preparations scratched from the rectum C. Postmortem examination: to confirm suspected infection 3. Immunological methods: ELISA, Dot-ELISA, IHA 4. PCR-based methods: specific PCR assay

Control Measures 1. Treatment of infected animals: A. Praziquantel (吡喹酮) which is used in the treatment of human schistosomosis is also effective in animals. B. Niridazole (硝唑咪) and trichlorfon (敌百虫),

Control Measures 2. Prevention of infection: A. Killing of snails: together with the development and modernization of agriculture; chemical killing of snails.

B. Management of animal and human faeces: 人有厕所；人畜粪便入厕并发酵或建沼气池 C. Prevention of reinfection of human and animals: avoid contact with cercaria! Safe drinking water, no wading in possibly infected water, 结合灭螺实行轮牧(Rotational Grazing)