Text book of Human Parasitology Edited by Wu Zhongdao(吴忠道)、 Zheng Xiaoyin(郑小英) chizogor Section I INTRodUCTION TO PARASITOLOGY
Text Book of Human Parasitology Edited by Wu Zhongdao(吴忠道)、Zheng Xiaoyin(郑小英) Section I INTRODUCTION TO PARASITOLOGY
Parasitology(寄生虫学), the study of parasites(寄生虫) and their relationships to their hosts(TE=E), is one of the most fascinating areas of the biology. While it is entirely proper to classify many bacteria(细菌) and fungi(真菌) and all viruses as parasites, parasitology has traditionally been limited to parasitic protozoa(原虫), helminthes(蠕虫), and arthropods(节 肢动物), as well as those species of arthropods that serve as vectors(媒介) for parasites. It follows, then, that parasitology encompasses elements of protozoology (Rs), helminthology (蠕虫学), and medical arthropodology(医学节肢动物学) Human parasitology, an important part of parasitology, study the medical parasites including their morphology(形态学, life cycle(生活史), the relationship with host and environment.The objectives are to study the way or the measurement of parasitic diseases control IMPORTANCE OF PARASITOLOGY Why do students need to learn the course now? In part time, parasitic infections or parasitic diseases were the most common diseases in the world. Therefore, parasitology played important ole on the medicine and public health, none neglect the important of parasitology. with the nearly 杀虫剂),an antiparasitic agents, it was for a time widely believed that the infectious diseases would for all practical purposes disappear from the clinical scene. Someone has asked the question, why do medical students still need to learn parasitology? Befor let ep of parasitic diseases in th world. According to the who(世界卫生组织)2001 year report parasitic diseases is still an important human diseases. In the world, 210 million people reside in the endemic areas of alaria(E#), 10 million cases with malaria occur every year; 20 million infected individuals was estimated in the world So TDR/WHO has proclaimed that 10 major unconquered human tropical diseases(热带病), African trypanosomiasis(非洲锥虫), Dengue(登革 热), Leishmaniasis(利什曼病), Malaria(疟疾), Schistosomiasis(血吸虫病), Tuberculosis (结核病), Chagas disease(夏格病又称美洲锥虫病), Leprosy(麻风), Lymphatic filariasis (淋巴丝虫病), Onchocerciasis(盘尾丝虫病). Among them7 diseases are parasitic in the traditional sense. In addition, DDT and other insecticides(s fill) not only have failed to eliminate the vectors of malaria, schistosomiasis, and other parasitic diseases but have themselves brought on problems too well-known to require mention here. The development of resistance to the synthetic antimalarials has been an ominous occurrence in recent years. The increased mobility of large segments of the population, and popularity of the tropics and subtropics as vacation areas, exposes them to a largely undiminished threat of parasitic infection, and the speed of transportation ensures that many return to their native shores before their infections become patent For these reasons it remains necessary that all physicians have some familiarity with the parasitic diseases. no matter ho Modifications of the environment maybe have brought about major increases in parasitic diseases, flooding of vast areas has resulted in new habitats for the snail hosts of schistosomiasis Global warming is suggested as a possible reason for the eventual spread of diseases now seen primarily in the tropics to more temperate climes. An important development of recent years has been the appearance of the human immunodeficiency virus(HIV) and its sequel, the immunodeficiency syndrome(AIDS), which results in greatly increased prevalence and severity of a number of parasitic, viral, and bacterial diseases. As immunosuppression becomes more
1 Parasitology（寄生虫学）, the study of parasites（寄生虫） and their relationships to their hosts（宿主）, is one of the most fascinating areas of the biology. While it is entirely proper to classify many bacteria（细菌） and fungi（真菌） and all viruses as parasites, parasitology has traditionally been limited to parasitic protozoa（原虫）, helminthes（蠕虫）, and arthropods（节 肢动物）, as well as those species of arthropods that serve as vectors（媒介）for parasites. It follows, then, that parasitology encompasses elements of protozoology（原虫学）, helminthology （蠕虫学）, and medical arthropodology（医学节肢动物学）. Human parasitology, an important part of parasitology, study the medical parasites including their morphology(形态学), life cycle（生活史）, the relationship with host and environment. The objectives are to study the way or the measurement of parasitic diseases control. IMPORTANCE OF PARASITOLOGY Why do students need to learn the course now? In part time, parasitic infections or parasitic diseases were the most common diseases in the world. Therefore, parasitology played important role on the medicine and public health, none neglect the important of parasitology. With the nearly simultaneous development of antibiotic drugs, synthetic pesticides（杀虫剂）, and various antiparasitic agents, it was for a time widely believed that the infectious diseases would for all practical purposes disappear from the clinical scene. Someone has asked the question, why do medical students still need to learn parasitology? Before answer the question, let me review the epidemic situation of parasitic diseases in the world. According to the WHO（世界卫生组织） 2001 year report, parasitic diseases is still an important human diseases. In the world, 210 million people reside in the endemic areas of malaria（疟疾）, 10 million cases with malaria occur every year; 20 million infected individuals was estimated in the world. So TDR/WHO has proclaimed that 10 major unconquered human tropical diseases（热带病）, African trypanosomiasis（非洲锥虫）, Dengue（登革 热）, Leishmaniasis（利什曼病）, Malaria（疟疾）, Schistosomiasis（血吸虫病）, Tuberculosis （结核病）, Chagas disease（夏格病又称美洲锥虫病）, Leprosy（麻风）, Lymphatic filariasis （淋巴丝虫病）, Onchocerciasis（盘尾丝虫病）. Among them 7 diseases are parasitic in the traditional sense. In addition, DDT and other insecticides（杀虫剂） not only have failed to eliminate the vectors of malaria, schistosomiasis, and other parasitic diseases but have themselves brought on problems too well-known to require mention here. The development of resistance to the synthetic antimalarials has been an ominous occurrence in recent years. The increased mobility of large segments of the population, and popularity of the tropics and subtropics as vacation areas, exposes them to a largely undiminished threat of parasitic infection, and the speed of transportation ensures that many return to their native shores before their infections become patent. For these reasons it remains necessary that all physicians have some familiarity with the parasitic diseases, no matter how “exotic”. Modifications of the environment maybe have brought about major increases in parasitic diseases, flooding of vast areas has resulted in new habitats for the snail hosts of schistosomiasis. Global warming is suggested as a possible reason for the eventual spread of diseases now seen primarily in the tropics to more temperate climes. An important development of recent years has been the appearance of the human immunodeficiency virus(HIV) and its sequel, the acquired immunodeficiency syndrome(AIDS), which results in greatly increased prevalence and severity of a number of parasitic, viral, and bacterial diseases. As immunosuppression becomes more
widespread, not simply because of AIDS, but also as necessitated by organ transplantation, the result of cancer chemotherapy, or the indiscriminate release of toxic chemicals and carcinogens into environment, heretofore unknown or extremely rare infections are being reported from human These are the reason why the course on Human or Medical Parasitology has been keeping Table I-I Current disease portfolio( from WHO report 2001) Disease burden Deaths DALYs*(thousands) (thousands) tegory Male Female Total Male Female 1,585 1,013 trypanosomiasis Leishmaniasis 1,810 1.067 Malaria 40,2131923720,9761,080 Chagas disease Leprosy 2223333 *DALY: disability- adjusted life years((失能调整生命年) In our country, various parasites have long been recognized as one of the important endemic diseases for many years. In the early 1950s the estimated number of people suffered from schistosomiasis totaled cases 10 million, and that from malaria and filariasis, 30 million each Since the founding of the People's Republic, the Chinese government has paid great attention to investigation and control of parasites, with particular emphasis on the five major ones,i.e schistosomiasis, malaria, filariasis, hookworm diseases and kala azar. Through 50 years'endeavor outstanding achievements have obtained Nevertheless, schisto somiasis is still prevalence in lake-marsh and mountain regions along Changjiang river; at the present, falciparum malaria(恶性疟疾) has not been under effective control in several southern provinces due to the emergence of multi-drug resistar ecological characteristics of the vector mosquito, Anopheles dirus(大劣按蚊) population migration. Besides, a nationwide survey conducted in 1988-1992 disclosed a striking number of parasite-infected population, and a high proportion of polyparasitism(多虫寄生)as well, e.g., overall prevalence of parasites was 59.67%(62.632-0 339%), and more than 700 million cases of infected individuals was estimated in China Although soil-transmitted (EEt) parasites infection have been reduced significantly with improvement of food-transmitted frFt) parasite infection, such as infection of clonorchis, have been become a new public health problem for dietary habits So it is considered that parasitic infection /or parasitic diseases are still one of the important problems in public health in our country. As a candidate for doctor, to learn some knowledge of parasitology is necessary GENERAL CONSIDERATION Medical(human) Parasitology consists of medical protozoology, medical helminthology
2 widespread, not simply because of AIDS, but also as necessitated by organ transplantation, the result of cancer chemotherapy, or the indiscriminate release of toxic chemicals and carcinogens into environment, heretofore unknown or extremely rare infections are being reported from human. These are the reason why the course on Human or Medical Parasitology has been keeping TableⅠ-Ⅰ-1Current disease portfolio(from WHO report 2001) TDR disease category Disease burden DALYs* (thousands) Deaths (thousands) Total Male Female Total Male Female African trypanosomiasis 1 1,585 1,013 572 50 32 18 Dengue 1 433 286 147 12 8 4 Leishmaniasis 1 1,810 1,067 744 41 23 18 Malaria 2 40,213 19,237 20,976 1,080 522 558 Schistosomiasis 2 1,713 1,037 676 11 8 3 Tuberculosis 2 35,792 21,829 13,962 1,660 1,048 613 Chagas disease 3 680 360 320 21 12 9 Leprosy 3 141 76 65 2 2 1 Lymphatic filariasis 3 5,549 4,245 1,304 0 0 0 Onchocerciasis 3 951 549 402 0 0 0 * DALY：disability-adjusted life years(失能调整生命年) In our country, various parasites have long been recognized as one of the important endemic diseases for many years. In the early 1950s, the estimated number of people suffered from schistosomiasis totaled cases 10 million, and that from malaria and filariasis, 30 million each. Since the founding of the People’s Republic , the Chinese government has paid great attention to investigation and control of parasites, with particular emphasis on the five major ones, i.e. schistosomiasis, malaria, filariasis, hookworm diseases and kala azar. Through 50 years’ endeavor, outstanding achievements have obtained. Nevertheless, schistosomiasis is still prevalence in lake-marsh and mountain regions along Changjiang River; at the present, falciparum malaria（恶性疟疾） has not been under effective control in several southern provinces due to the emergence of multi-drug resistant strain and ecological characteristics of the vector mosquito, Anopheles dirus（大劣按蚊）, as well as population migration. Besides, a nationwide survey conducted in 1988-1992 disclosed a striking number of parasite-infected population, and a high proportion of polyparasitism（多虫寄生） as well, e.g., overall prevalence of parasites was 59.67%(62.632±0.339%), and more than 700 million cases of infected individuals was estimated in China Although soil-transmitted（土源性） parasites infection have been reduced significantly with improvement of living conditions, food-transmitted（食源性）parasite infection, such as infection of clonorchis, have been become a new public health problem for dietary habits. So it is considered that parasitic infection /or parasitic diseases are still one of the important problems in public health in our country. As a candidate for doctor, to learn some knowledge of parasitology is necessary. GENERAL CONSIDERATION Medical (human) Parasitology consists of medical protozoology, medical helminthology
and medical arthropodology Symbiosis(#+E) Symbiosis means"living together of both members of species. Any organism that spends a portion or all its life intimately associated with another living organism of a different species is known as a symbiont( or symbiote ), and the relationship is designated as symbiosis. The term symbiosis, as used here, does not imply mutual or unilateral physiologic dependency; rather, it is used in its original sense(living together )without any reference to benefit "or"damage"to the symbionts. There are at least three categories of symbiosis whose are commonly recognized: commensalisms, mutualism and parasitism Commensalism(#tf) It was from Latin for"eating at same table" denotes an association which is beneficial to one partner and at least not disadvantageous to the other The two partners can survive independently. Mutualism(互利共生) Mutualism is an association in which the mutual ist and the host depend on each other physiologically. It is seen where such associations are beneficial to both orga Parasitism(RHE) Parasitism is onother type of symbiotic relationship between two organisms: a parasite(寄生虫), usually the smaller of the two, and a host(宿主), upon which the parasite is physiologically dependent. The relationship may be permanent, as in the case of worms found in the vertebrate intestine as with female mosquitoes. some leeches, and ticks, which feed intermittently on host blood. In other words, it is a symbiotic relationship in which one animal, the host, is to some degree injured through the activities of the Parasite(REs) Its biological definition is an animal or plant which lives in or upon another organism(technically called its host)and draws its nutriment directly from it By this definition all infectious agents, viruses, bacteria, fungi, protozoa, and helminths are parasites, but traditionally protozoa, helnimths and medical arthropod(节肢动物), so called parasites,are tudied in medical or human Parasitology. Therefore,, the textbooks of parasitology today deal only with protozoa, helminthes and some arthropod The parasites broadly are of two types: endoparasite(体内寄生虫) and Ectoparasite(体外 REs). The parasite which lives within the host is called the endoparasite(e. g, leishmania) Invasion by the parasite is called infection. Usually, the endoparasites cause most human diseases The endoparasites include 3 types, such as obligate parasite, facultative parasite and accidental parasite. Obligatove parasites(专性寄生虫) are physiologically dependent upon their hosts and usually cannot survive if kept isolated from them(eg, Toxoplasma gondi 5 s). Facultative parasites(兼性寄生虫), on the other hand, are essentially free-living organisms that are capable of becoming parasitic if placed in a situation conductive to such a mode. An example of facultative parasite is Strongyloides stercoralis(粪类圆线虫). Accidental parasites(偶然寄生 sh), the parasite which attacks an unusual host. Ectoparasite, the parasite which lives on the outer surface or in the superficial tissues of the host(e.g, lice). The infection by these parasites is called infestation(侵扰) Host Host is defined as an organism which harbours the parasite and provides the nourishment and shelter. These hosts, in comparison to their parasites are relatively larger in size The hosts may be of the following types: definitive host, intermediate host, reservoir host and paratenic host etc. 1)Definitive host(AHE E) The hosts which harbour the adult parasites(e. g, taenia
3 and medical arthropodology. Symbiosis（共生） Symbiosis means “living together of both members of species. Any organism that spends a portion or all its life intimately associated with another living organism of a different species is known as a symbiont( or symbiote), and the relationship is designated as symbiosis. The term symbiosis, as used here, does not imply mutual or unilateral physiologic dependency;rather, it is used in its original sense(living together)without any reference to “benefit” or “damage” to the symbionts. There are at least three categories of symbiosis whose are commonly recognized: commensalisms, mutualism and parasitism. Commensalism（共栖） It was from Latin for “eating at same table”, denotes an association which is beneficial to one partner and at least not disadvantageous to the other. The two partners can survive independently. Mutualism（互利共生） Mutualism is an association in which the mutualist and the host depend on each other physiologically. It is seen where such associations are beneficial to both organisms(partners). Parasitism（寄生） Parasitism is onother type of symbiotic relationship between two organisms: a parasite（寄生虫）, usually the smaller of the two, and a host（宿主）, upon which the parasite is physiologically dependent. The relationship may be permanent ,as in the case of tapeworms found in the vertebrate intestine, or temporary, as with female mosquitoes, some leeches, and ticks, which feed intermittently on host blood. In other words, it is a symbiotic relationship in which one animal, the host, is to some degree injured through the activities of the other animal, the parasite. Parasite（寄生虫） Its biological definition is an animal or plant which lives in or upon another organism(technically called its host) and draws its nutriment directly from it. By this definition all infectious agents, viruses, bacteria, fungi, protozoa, and helminths are parasites, but traditionally protozoa , helnimths and medical arthropod（节肢动物）, so called parasites, are studied in medical or human Parasitology. Therefore,, the textbooks of parasitology today deal only with protozoa, helminthes and some arthropod. The parasites broadly are of two types: endoparasite（体内寄生虫） and Ectoparasite（体外 寄生虫）. The parasite which lives within the host is called the endoparasite(e.g, leishmania). Invasion by the parasite is called infection. Usually, the endoparasites cause most human diseases. The endoparasites include 3 types, such as obligate parasite, facultative parasite and accidental parasite.Obligatove parasites(专性寄生虫) are physiologically dependent upon their hosts and usually cannot survive if kept isolated from them(e.g., Toxoplasma gondii 弓形虫). Facultative parasites(兼性寄生虫)，on the other hand, are essentially free-living organisms that are capable of becoming parasitic if placed in a situation conductive to such a mode. An example of a facultative parasite is Strongyloides stercoralis（粪类圆线虫）. Accidental parasites（偶然寄生 虫）, the parasite which attacks an unusual host. Ectoparasite, the parasite which lives on the outer surface or in the superficial tissues of the host(e.g., lice). The infection by these parasites is called infestation(侵扰). Host Host is defined as an organism which harbours the parasite and provides the nourishment and shelter. These hosts, in comparison to their parasites are relatively larger in size. The hosts may be of the following types: definitive host, intermediate host, reservoir host and paratenic host etc. 1) Definitive host（终宿主） The hosts which harbour the adult parasites(e.g., Taenia
saginata causing intestinal taeniasis), most highly developed form of the parasite(e.g Trypanosoma cruci causing African sleeping sickness) or where the parasite replicates sexually(e. g, Paragonimus westermani) are called the definitive hosts. The definitive hosts may be human or non-human living things 2) Intermediate host(中间终主) The hosts which harbour the larval stages of parasite development or the asexual forms of the parasite are called intermediate host. Some times two different hosts may be required to complete different larval stages. These are known as the first and second intermediate hosts respectively(e. g snails t] are the first intermediate hosts and fresh water fish are the second intermediate hosts for Clonorchis sinensi AfRs s 3) Reservoir host(保虫宿主) The animal which harbours the parasites and serves as an important source of infection to other susceptible hosts are known as reservoir host(e.g,water buffalo is the reservoir host for schistosomiasis血吸虫病) 4) Paratenic host or transport host(转续宿主) The larva of some parasites can invade a non-normal host, but can not develop, and only keep the larva stage. If the larva enter a normal definitive host, it can continue to develop into adult worm. The non-normal host is called paratenic lost or transport host. It functions as a transport or carrier host TAXONOMY(分类学) ature(命名法) Nature”1758), each parasite has two names: a Genus(属名) and a Species name(种名). These names are derived either from (1)Greek or Lati n wor (2) Names of their discoverers (3) Geographical area where found (4)Hosts in which parasites are found, or (5)Habitat of the parasite The correct scientific name of the parasite consists of the genus and species to which belong, the name of the designator and the year in which it was discovered(e.g, Angiostrongylus cantonensis管圆线虫Chen,1935) Dougherty,1946) The animal parasites of human and most vertebrates are contained in five or more major ubdivisions or phyla (IT) Phylum Sarcomastigophora(肉鞭毛虫门). This phylum is divided into two subphyla:the Mastigophora or flagellates(鞭毛虫纲), and the Sarcodina or amebae(肉足纲) Phylum Apicomplexa(JiAl]) Members of this phylum are tissue parasites. Apicomplexa have a complex life cycle with alternating sexual and asexual generations. Phylum Microspore(微孢子门) Members of the Microspora are minute intracellular parasites of many kinds of vertebrates and invertebrates, and they differ significantly in structure from the Apicomplexa. Microsporidia rarely cause diseases in immunocompetent persons, but many do so with greater frequency in immunosuppressed persons Phylum Ciliophora(纤毛虫纲) The ciliates include a variety of free- living and symbiotic species. The only ciliate parasite of human is Balantidium coli, found in the intestinal tract. Although rare, it is important, as it may produce severe intestinal symptoms Phylum Platyhelminthes(扁形动物门) The Platyhelminthes, or flatworms,are multicellular animals characterized by a flat bilaterally symmetric body. Most flatworms are
4 saginata causing intestinal taeniasis), most highly developed form of the parasite(e.g., Trypanosoma cruzi causing African sleeping sickness) or where the parasite replicates sexually(e.g., Paragonimus westermani) are called the definitive hosts. The definitive hosts may be human or non-human living things. 2) Intermediate host（中间终主） The hosts which harbour the larval stages of parasite development or the asexual forms of the parasite are called intermediate host. Some times two different hosts may be required to complete different larval stages. These are known as the first and second intermediate hosts respectively(e.g., snails 钉螺 are the first intermediate hosts and fresh water fish are the second intermediate hosts for Clonorchis sinensi 肝吸虫 s). 3) Reservoir host（保虫宿主） The animal which harbours the parasites and serves as an important source of infection to other susceptible hosts are known as reservoir host(e.g., water buffalo is the reservoir host for schistosomiasis 血吸虫病). 4) Paratenic host or transport host（转续宿主） The larva of some parasites can invade a non-normal host, but can not develop, and only keep the larva stage. If the larva enter a normal definitive host, it can continue to develop into adult worm. The non-normal host is called paratenic host or transport host. It functions as a transport or carrier host. TAXONOMY（分类学） According to the biomial nomenclature（命名法） as suggested by Linnaeus(“Systema Nature” 1758),each parasite has two names: a Genus(属名) and a Species name（种名）. These names are derived either from ⑴ Greek or Latin words ⑵ Names of their discoverers ⑶ Geographical area where found ⑷ Hosts in which parasites are found, or ⑸ Habitat of the parasite The correct scientific name of the parasite consists of the genus and species to which it belong, the name of the designator and the year in which it was discovered(e.g., Angiostrongylus cantonensis 管圆线虫(Chen, 1935) Dougherty, 1946). The animal parasites of human and most vertebrates are contained in five or more major subdivisions or phyla（门）. Phylum Sarcomastigophora(肉鞭毛虫门). This phylum is divided into two subphyla: the Mastigophora or flagellates(鞭毛虫纲), and the Sarcodina or amebae（肉足纲）. Phylum Apicomplexa(顶复门) Members of this phylum are tissue parasites..Apicomplexa have a complex life cycle with alternating sexual and asexual generations. Phylum Microspora(微孢子门) Members of the Microspora are minute intracellular parasites of many kinds of vertebrates and invertebrates, and they differ significantly in structure from the Apicomplexa. Microsporidia rarely cause diseases in immunocompetent persons, but many do so with greater frequency in immunosuppressed persons. Phylum Ciliophora(纤毛虫纲) The ciliates include a variety of free-living and symbiotic species. The only ciliate parasite of human is Balantidium coli, found in the intestinal tract. Although rare, it is important, as it may produce severe intestinal symptoms. Phylum Platyhelminthes( 扁 形 动物 门) The Platyhelminthes, or flatworms, are multicellular animals characterized by a flat, bilaterally symmetric body. Most flatworms are