Medical Parasitology --Introduction Department of Medical Parasitology

Introduction to Medical Parasitology Definition of medical parasitology Significances of medical parasitology Conceptions related to medical parasitology Relationships between parasites and hosts Basic factors of transmission of parasitic diseases Preventive measures of parasitic diseases

Introduction to Medical Parasitology Definition of medical parasitology Significances of medical parasitology Conceptions related to medical parasitology Relationships between parasites and hosts Basic factors of transmission of parasitic diseases Preventive measures of parasitic diseases

What is Parasitology? A parasite is an organism that live on or within another organism called the host. Parasitology is a science of studying parasitism and a discipline dealing with the biology of parasites (including its morphology, embryology, physiology, biochemistry and nutrition, etc.), ecology of parasitism with emphasis on parasite- host and parasite-environment interactions.

Since the parasites studied in this discipline involve parasitic protozoa, parasitic helminthes, certain lesser groups of worms, parasitic arthropods, and the vectors of parasites, that is, parasitology is largely an amalgamation of protozoology, helminthology, entomology and acarology. Parasitology has also been subdivided into medical or human parasitology, veterinary parasitology, fish parasitology and plant nematology. What is Parasitology?

What is Medical Parasitology? Medical parasitology or human parasitology is restricted to studying those parasites that are living in or on the body of humans and with aspects of the host-parasite relationship having medical significance. In other words, medical parasitology is the subject which deals with the parasites that infect man, the diseases caused by them, clinical picture and the response generated by man against them.

Pathogenic Biology In modern biomedicine, medical parasitology and medical microbiology, which are integrated into pathogenic biology, are in the same scope of pathogenic organisms. Pathogenic biology which focuses on the biological causes to human infectious diseases (biological etiology), is usually comprised in preventive medicine and is also considered as the foundation of clinical infectious or communicable diseases and public health.

Pathogenic Biology Pathogenic biology involves the biological features of pathogenic organisms, the relationships between pathogenic parasites and hosts and their environment, the pathogenic factors and the related pathogenesis, the laboratory diagnosis, the transmission and prevalence, and the prevention and control of these diseases infected with pathogenic organisms. Microbiology--- Pathogen (Microbe) : viruses, bacteria, and fungi. Parasitology--- Pathogen (Parasites) : protozoa, helminthes, and arthropods.

Medical Parasitology Parasites Parasitic diseases Morphology Life Cycle Pathogenesis Diagnosis TreatmentTransmissionPrevention

Medical protozoology Medical helminthology Medical arthropodology Medical parasitology i.e. Medical entomology

Preclinical Public Health & Clinical Biology Medicine Preventive Medicine Medicine Pathogenic Biology Medical Parasitology & Medical Microbiology Medical Parasitology in Medicine Microbiology

Overseas Medical Education In USA, UK, and other countries, medical microbiology includes medical microbiology and parasitology. Medical parasitology is not a independent curriculum. Curriculum Reform in China Before 1997, two independent curricula Since 1997, a compulsive curriculum---- Pathogenic biology. However, in our school, microbiology and parasitology are two independent curricula in medical education.

Biology,Biochemistry,Anatomy, Histology,Physiology,Immunology Medical Parasitology Public Health & Clinical Preventive Medicine Medicine Medical Parasitology in Medical Education

Curriculum Plan Lectures ---- introduce main parasites and related parasitic diseases Experimental observations ---- observe the morphologic characteristics of parasites by microscopy or naked eye Final examination

1. Wang Shiping & Ye Shiying. Textbook of Medical Microbiology and Parasitology (1st Edition) ， Gerald D Schmidt & Larry S Roberts. Foundation of Parasitology (3rd Edition) ， 8th ed, David T John, et al. Medical Parasitology (9th Edition) ， CDC Division of Parasitic diseases: 5. DPDx: Recommended References

Early written records 3000 to 400 BC, the first written records of parasitic infections come from Egyptian medicine, particularly the Ebers papyrus of 1500 BC discovered at Thebes. Intestinal roundworms and tapeworms. 800 to 300 BC, writings of Greek physicians such as Hippocrates. Worms from fishes, domesticated animals, and humans to 300 BC, writings of physicians from China to 200 BC, from India. 700 BC to 400 AD, from Rome. Latter part of the first millennium, from the Arab Empire. Arabic physician Avicenna (AD 980 to 1037), wrote important medical works that contain a great deal of information about diseases clearly caused by parasites. He recognized not only Ascaris, Enterobius, and tapeworms but also the guinea worm, Dracunculus medinensis. History of Human Parasitology

Modern times Manson in 1879 filariasis Laveran in 1880 malaria parasite Ross in 1897 malaria life cycle Bruce in and Chagas in 1908 trypanosomiasis Leishman and Donovan in leishmaniasis …… 1879 (Ringer), 1880 (Manson) : Paragonimus westermani 1875 (McConnell) : Clonorchis sinensis 1905 (Logan) : Schistosoma japonicum in China …… History of Human Parasitology

In England Manson became Medical Advisor to the Colonial Office and in this capacity persuaded the then Secretary of State for the Colonies, Joseph Chamberlain, of the need for providing facilities in Britain for educating doctors in tropical diseases. One consequence of his influence was the creation of School of Tropical Medicine in both Liverpool and London in 1898 Patrick Manson( ) “Father of modern tropical medicine” The first President (and Ronald Ross Vice-President) of the Society of Tropical Medicine and Hygiene (1907) The first to discover (1877–79) that an insect (mosquito) can be host to a developing parasite (the worm Filaria bancrofti) that is the cause of filariasis

Alphonse Laveran 1907 Nobel Laureate in Medicine in recognition of his work on the role played by protozoa in causing diseases Ronald Ross 1902 Nobel Laureate in Medicine for his work on malaria, by which he has shown how it enters the organism and thereby has laid the foundation for successful research on this disease and methods of combating it

(Dr. Fuqing Yan ）： Local epidemic investigations on schistosomiasis and malaria around Changsha （ Dr. Fuqing Yan ） : Investigation and control researches on hookworm infection at Pingxiang county （ Beijing Xie-He medical college ）： Department of Parasitic biology 1928 （ Dr. Shilv Hong ）： Hangzhou institute of tropical disease, the first academic organization in China on parasitology 1932: Department of parasitology, Central experimental academy on hygiene Thereafter: Shanghai medical college, Lingnan university, Xiangya school of medicine, Western China medical school, Qilu university…… Human Parasitology in China

Classification of parasites Protozoa Parasites Helminthes Arthropods Nematodes Trematodes Cestodes (Endoparasite) (Ectoparasite) (Unicellular) (Multicellular )

RBC Protozoa Plasmodium

Trematodes cercariae Schistosome

Paragonimus westermani (Lung fluke)

Tapeworm Cestodes

Nematode Ascaris lumbricoides

Hookworm

Medical Medical arthropods Fly Mosquito Sandfly Flea Louse Hard tickSoft tick

229 species in total Nematodes species Trematodes species Cestodes species Protozoa species Others species Common human parasites -- around 80 species Human parasites in China

----According to parasitic sites *Intestinal tract parasites ： 30+ species Ascaris lumbricoides （ round worm ） Trichuris trichiura （ whip worm ） Enterobius vermicularis （ pinworm ） Hookworm Fasciolopsis buski （ intestine fluke ） Taenia solium Entamoeba histolytica, etc. Classification in clinic

----According to parasitic sites Classification in clinic *Other tract parasites ： 10+ species esophagus : Uongylonema pulchrum trachea : Mammomonogamus biliary tract : Liver fluke urogenital tract : Trichomonas vaginalis, etc. * Blood vessel parasites ： 5+ species Schistosome, Filarial worms, Angiostrongylus cantonensis, etc.

----According to parasitic sites Classification in clinic *Tissue parasites ： 20+ species brain : Angiostrongylus cantonensis eye : Thelazia callipaeda lung : Lung fluke kidney : Dioctophyma renale skin: Sarcoptes scabiei, etc. ……

----According to parasitic sites Classification in clinic * Intracellular parasites ： 7+ species Plasmodium Leishmania Toxoplasma gondii Trichina spiralis, etc. * Ectoparasite / Vectors ： 60+ species Louce, Flea, Mosquito, Fly, Sand fly, Tabanid fly, Tick, gamasid mite, etc.

International travel Contamination of water supply Immigrants from endemic areas Popularity of household pets Increasing popularity of exotic regional foods Use of antibiotics and immuno-suppressive drugs Spread of AIDS Undercooked meats and raw fish Ingestion of improperly washed fruits, vegetables Where and how we can get parasites

Introduction to Medical Parasitology Definition of medical parasitology Significances of medical parasitology Conceptions related to medical parasitology Relationships between parasites and hosts Basic factors of transmission of parasitic diseases Preventive measures of parasitic diseases

1. Common ailment and frequently encountered disease Why should we study Parasitology? Hainan Guangxi Fujian Sichuan Guizhou Zhejiang Jiangxi Hunan Guangdong Heilongjiang % The first survey on parasitic infection completed in 1992 indicated the total infection rate of human parasites in China was 62.63%, number of infections was about more than 700 million, geohelminthes infection for the most

Why should we study Parasitology? Through comprehensive prevention and control in China, total worms infection rate in 2004 dropped from 55.27% to 21.4%. Estimated total number of infections of roundworm, hookworm, whipworm dropped from 536 million in 1990, to about 129 million people (76% reduction ). But in central and southern China, soil -borne nematode infection rate was still as high as 20.1 % to 56.2% 1. Common ailment and frequently encountered disease

In 1947, N. Stoll estimated the total number of infections of roundworm, whipworm and hookworm were 644 million (30%) ， 355 million (16%) ， 457 million(21%), respectively. Fifty years later, in 1997, the numbers were 1273million (24%) ， 902million (17%) and 1277million (24%), respectively. The prevalence of intestinal nematodes did not change, and there was a significant increase in the actual number of infections, almost in developing countries.

Why should we study Parasitology? 2. Severe consequence of parasitic infection Parasitic infection result in the decline of work ability and quality of life, teratogenesis, disability, death, and carcinogenesis induction

Damage to vital organs Brain Eye Lung Liver Heart Eye Why should we study Parasitology?

Schistosomiasis mesenteric veins via hepatic portal system ascites

Damage to the skin or muscle

Affect the growth, development/teratogenesis

Why should we study Parasitology? 3. WHO/TDR focuses on infectious diseases Accoding to WHO statistics, parasites are the cause of more human deaths than anything else apart from HIV/AIDS and tuberculosis(TB), one living person in ten suffers from one or more of eight major tropical diseases: malaria, schistosomiasis, lymphatic filariasis, onchocerciasis, leprosy, sleeping sickness,Chagas disease,and leishmaniasis >,

The main target diseases of WHO communicable disease programs Malaria Schistosomiasis and intestinal parasitic infections Filariasis (lymphatic filariasis, onchocerciasis) Leishmaniasis Trypanosomiasis (sleeping sickness, Chagas disease) Dracunculiasis Leprosy Tuberculosis Poliomyelitis, AIDS,Dengue fever, etc.

Threatened Endemic countries Deaths dalys(Burden of disease) population (million) (thousand) (million) Malaria Schistosomiasis Trypanosomes Filaria Ascaris Trichuris Hookworm Dalys: Disability adjuststed life years --Reflect the extent of parasitic diseases on the health damage “Top ten” of human parasites, based on WHO estimated

Tropical diseases are still neglected by scientific community and medical education, and are still relatively isolated from the mainstream of modern biomedicine in the western world, as well as in the developing world, including China, but they remain one of major health problems in the world and particularly, still rank exceedingly high in most of developing countries Still neglected ! Neglected Tropical Diseases (NTD)

Burden of disease due to NTDs World Health Report Lymphatic Filariasis 5,654,000 Soil-transmitted helminthiasis 4,706,000 Kala-azar 2,357,000 Trachoma 2,329,000 Schistosomiasis 1,760,000 African Sleeping Sickness 1,598,000 Onchocerciasis 987,000 Chagas Disease 649,000 Leprosy 177,000 Buruli Ulcer <100,000 Guinea-worm <100,000 Total Neglected Disease 20,217,000 HIV-AIDS 84,429,000 Malaria 42,280,000 Revised estimates (The Lancet) Hookworm disease 22.1 million Ascariasis 10.5 million Trichuriasis 6.4 million Lymphatic Filariasis 5.8 million Schistosomiasis 4.5 million Trachoma 2.3 million Leishmaniasis 2.1 million Trypanosomiasis 1.5 million Chagas Disease 0.7 million Onchocerciasis 0.5 million Leprosy 0.2 million Dracunculiasis <0.1 million Total 56.6 million

Diseases （ patients ） Malaria 30 million Schistosomiasis million 0.39 million Filariasis million basically eradicated in 1994 (0.1 million ， 1999 ） Leishmaniasis 0.53 million basically eradicated in Hookworm disease 190 million (infection rate 70%) 39.3 million （ 2004 ） Hydatid disease: 0.6 million, Ascariasis: 86 million, Hookworm disease: million, Trichuriasis: 29million (2004) Clonorchiasis:12.5 million (2005) Why should we study Parasitology? 4. “Top five” parasitic diseases in China

Introduction to Medical Parasitology Definition of medical parasitology Significances of medical parasitology Conceptions related to medical parasitology Relationships between parasites and hosts Basic factors of transmission of parasitic diseases Preventive measures of parasitic diseases

Conceptions related to medical parasitology Symbiosis Parasite and type of parasites Host and common type of host Life cycle and type of life cycle

Symbiosis The relationship between two living things (animals). Two living things live together and involve protection or other advantages to one or both partner. Commensalism Mutualism Parasitism*

Commensalism Both partners are able to lead independent lives, but one may gain advantage from the association when they are together and least not damage to the other A female pea crab in the mantle cavity of its mussel host. The crab does not damage the mussel and uses its shell purely for protection Mussel

Mutualism An association which is beneficial to both living things A selection of ciliates from the rumen of cattle or sheep. The rumen contains enormous numbers of ciliates that break down cellulose in the feed

Parasitism An association which is beneficial to one partner and harmful to the other partner. The former that is beneficial to is called parasite, the latter that is harmful to is called host. e.g., Human / Hookworm

Protozoa Parasites Helminthes Arthropods Nematodes Trematodes Cestodes (Endoparasite) (Ectoparasite) (Unicellular) (Multicellular ) Parasite and the type of parasites Parasite: an animal that is dependent on another animal (host) for its survival

Other classification Parasites may be classified according to different ways: Obligate parasite: a parasite which cannot survive in any other manner, e.g., filaria Facultative parasite: an organism which may exist in a free-living state and which if opportunity presents itself may become parasitic, e.g., Strongyloides stercoralis

Endoparasite and ectoparasite A parasite which lives in or on the body of the host is called endoparasite (protozoa and helminthes) or ectoparasite (arthropods)

Host and type of host Intermediate host : the host harboring the larvae or asexual stage of parasite Final host (definitive host) : the host harboring adult or sexual stage of parasite Host : an organism that harbors the parasite usually larger than the parasite

Host and type of host Reservoir host : animals harboring the same species of parasites as man, e.g., schistosome/human, buffalo Potential sources of human infection Paratenic host (transport host) : a host which acts as a transporting agent for the parasite and in which, the parasite, usually a larval stage, dose not undergo any further development but if they could go into a final host by accident it would continue to develop till sexual maturity, e.g., Paragonimus Westermani /human, wild boar

Life cycle and type of life cycle The direct type : only one host (final host, no intermediate host). e.g., Ascaris lumbricoides, Hookworm, and Enterobius vermicularis The indirect type : life cycle with more than one host (intermediate host and final host). e.g., plasmodium, lymphatic filaria Life cycle : the whole biological course of growth, development and reproduction of a parasite

Introduction to Medical Parasitology Definition of medical parasitology Significances of medical parasitology Conceptions related to medical parasitology Relationships between parasites and hosts Basic factors of transmission of parasitic diseases Preventive measures of parasitic diseases

Relationship between parasite and host injure to Parasites harbour in Host (animal or human) immune responses Effects of the parasites on the host Effects of the host on the parasites

Effects of parasites on the host Depriving the host of essential substance Hookworm Suck blood Anemia Mechanical damage of parasites on the host Ascaris Perforate/Obstruction Toxic Entamoeba histolytica Proteolytic enzyme Necrosis Inflammation and hypersensitivity Parasite antigen Immune system e.g., Anaphylaxis Immune response Allergy/ Hypersensitivity

Uptake of nutrition Pathogens utilize nutrition from host environment for their development and reproduction. Helminthes (nematodes or flukes --- have a gut and mouth) feed upon the surrounding tissues, body fluids or even host cell debris. Tapeworms (no gut or mouth) reply on the host’s daily intake by their body wall absorbing for their own food.

Mechanical damage of parasites Entering the cells: some protozoa must live in certain cells and reproduce. Finally result in the rupture of the host cells. Migration or penetration through tissue or organ Blockage and pressure: the intestinal lumen can be blocked by worms. Hydatid cyst in liver may reach volumes of 1-2 litres, it can cause severe damage to organ.

Toxic and hypersensitivity Toxin: many parasites can introduce or secret toxin and cause damage to host. Hypersensitivity: the metabolites, secretion, excretion or other products of parasites or dead worms may act as foreign antigen, to stimulate the immune system of host to produce immune response or hypersensitivity. Hypersensitivity is harmful to host, which may lead to severe or even fatal reaction.

Sudden rupture of hydatid cysts with release of large amounts of fluid could result in severe allergic reaction, sometimes lead to shock or death of patients

Effects of the host on the parasites Innate immunity Acquired immunity The host can produce certain degree resistance to parasites in human body or re- infection. The resistance (Immunity) is not very strong. In general, It does not wipe out parasites completely, but may limit the number of parasites and establishes balance with parasites

Innate immunity Barrier : prevent parasites to invade in certain degree. skin/mucous, membrance/placenta Acid in skin or stomach can cause damage of the parasites Phagocytosis of phagocyte Non-specific/effective against a wide range of parasitic infection/controlled by genetical factors. But not very strong

Acquired immunity Mechanism : cellular and humoral immunity Sterilizing immunity : wipe out the parasites completely, meanwhile get a long-term specific resistance to re-infection. Rare! Non-sterilizing immunity : wipe out most of the parasites, but not completely. Common! No parasite, no immunity

Introduction to Medical Parasitology Definition of medical parasitology Significances of medical parasitology Conceptions related to medical parasitology Relationships between parasites and hosts Basic factors of transmission of parasitic diseases Preventive measures of parasitic diseases

Basic factors of transmission of parasitic diseases Parasitic diseases Infectious diseases Transmission The source of the infection The routes of transmission The susceptible host The combined effect of those factors determine the dispersal and the prevalence of the parasites at a given time and place and regulate the incidence of the parasitic diseases in certain local population.

Source of the infection Patient : persons who have parasites in their body and show clinical symptoms Carrier : persons who have parasites in their body, not show symptoms Reservoir host : animals that harbor the same species of parasites as man, the parasites in animals sometimes can be transmitted into human

Routes of transmission Congenital transmission : from mother to infant, e.g., toxoplasmosis Contact transmission : direct contact or indirect contact with patients or infected animals, e.g., Trichomonas vaginalis Food transmission : the infectious stage of parasites contaminated food / the meat of the intermediate hosts containing infectious stage of parasites, e.g., Clonorchiasis

Water transmission : drink or contact the water contaminated the infectious stage of parasites, e.g., schistosome, Entamoeba histolytica Soil transmission : soil contaminated by feces containing the certain stage of parasites which can develop into infective stage, e.g., Ascaris lumbricoides, hookworm Arthropod transmission : vectors of certain parasitic diseases, e.g., plasmodium Routes of transmission

Susceptible host In general, people is the susceptible host (Why?). The parasite reaching a susceptible host must gain entrance and set up a favorable residence in order to complete its life cycle and cause the transmission of parasitic diseases.

Avenues of invasion Digestive tract : most common avenue of entrance. (food/ water transmission) Skin : infective larvae perforate skin and reach to body and establish infection. (soil/ water/ contact transmission) Blood : bloodsucking insects containing infective parasites bite the skin and inject parasites into human blood. (arthropod transmission)

Prevention measures of parasitic diseases Controlling the source of the infection: treatment of the patients, carriers and reservoir hosts Blocking the routes of transmission: managing feces and water resource, controlling or eliminating vectors and intermediate hosts Protecting the susceptible hosts: paying attention to health education/ personal hygiene, changing bad working/ eating habit, etc.