Human Parasitology. Shandong University Department of Parasitology He Shenyi （何深一 ） MD, Ph.D. Professor. Introduction to Human Parasitology. Concept of Human Parasitology The Scope of Human Parasitology Terms of Parasitology Parasites’ Harms to Man Human Immunity against Parasites
Department of Parasitology
He Shenyi （何深一 ）
MD, Ph.D. Professor
Parasitology claims those protozoa (single celled animals), helminths (worms) and arthropods whose existence depends on the availability of host animals It is also possible to argue about whether certain insects and mites are "temporary parasites" or "micro-predators", insects as a group belong to the discipline of Entomology, while ticks and mites are the concern of Acarology. The insects that are of most interest in human parasitology are those that are vectors of several parasitic infections.
Toxopasma gondii Cryptosporidium
Taenia saginata Echinococcus granulosus
Sandflies , Fleas
(1)Symbiosis（共同生活）Two different organisms live together and interact, in this association one partner lives in or on another one’s body. including 3 types:Mutualism, Commensalism, Parasitism.
(3)Commensalism（片利共生或共栖）is the association of two different organisms, in which one partner is benefited while the other neither benefited nor injured, such as E. coli and man.
(4) Parasitism（寄生关系）is the association of two different organisms, in which one partner is benefited while the other is injured, such as Ascaris lumbricoides and man.
(5) Parasite（寄生虫） In parasitism, it is the benefited partner. It is an animal organism which lives in or on the host in order to obtain nourishment and shelter from the host as well as does harms to the host.
(6) Host（宿主） In parasitism, it supplies the parasite with nourishment and shelter, it is the injured partner.
(7) Carrier（带虫者） A person who harbours parasite has no clinical symptoms, is an important source of infection in epidemiology.
(8) Definitive (final) host（终宿主）harbours adult or sexually reproductive stage of a parasite.
(9) Intermediate host（中间宿主）harbours larval or asexually reprodctive stage of a parasite, according to priority they are classified into first intermediate host, second intermediate host, third intermediate host.
(10) Reservoir hosts（保虫宿主）are the vertebrate hosts which harbour the same species of parasite at same stage as a human host. They are an important source of infection in epidemiology.
(11) Zoonosis（人兽共患病）refers to animal’s diseases which can be transmitted to man. (These animals infected with parasites are called reservoir hosts.)
(12) Paratenic host or transport host（转续宿主）is an abnormal host in which some parasitic larvae can survive but can’t develop into adults. If the larvae have a chance to enter their appropriate hosts, they can continue to develop into adults there.
(13)Larva migrans（幼虫移行症）means that the larvae living in their abnormal hosts in which they can not grow into adults but can wander everywhere and cause the local and systemic pathological lesions of the hosts.
(14)Life cycle（生活史） is the process of a parasite’s growth, development and reproduction, which proceeds in one or more different hosts depending on the species of parasites.
(15)Infective Stage（感染期）is a stage when a parasite can invade human body and live in it .
(16)Infective Route（感染途径）is the specific entrance through which the parasite invades the human body.
(17)Infective Mode（感染方式） means how the parasite invades human body, such as the cercariae of the blood fluke actively penetrate the skin of a swimming man and the infective ascaris eggs are swallowed by man.
(18) Alternation of Generation:
In life cycles of some parasites, there are the regular alternations of sexual and asexual reproductions , this phenomenon is called alternation of generation, such as the life cycle of Plasmodium vivax.
(19) Mechanical Transmission: Arthropods play a role of the transportation of pathogens, which is not indispensable for the disease transmission, such as flies carry typhoid bacilli, ascarid eggs and amoebic cysts.
(20) Biological Transmission: Pathogens have to spend a part of their life cycle in the vector arthropods in which they multiply or develop into the infective stage and then invade the human body under the help of the arthropod, such as Anopheles mosquitoes transmit malaria.
endoparasite Free living
temporary parasite Symbiosis Mutualism（互利共生）
permanent parasite Parasitism
obligatory parasite carrier
facultative parasite parasite Host
accidental parasite Patient
Final host Intermediate host Reservoir host Paratenic host
Zoonosis Larva migrans
6. Leprosy (replaced by HIV/AIDS)
Schistosomiasis - 200,000,000 infected
Malaria - 500,000,000 infected
Filariasis - 250,000,000 infected
Trypanosomiasis - 25,000,000 infected
Leishmaniasis - 1,200,000 infected
Leprosy - 1,300,000 infected
Approximately 25% of world's population infected by one of these.
1. Chronic diseases
2. No effective vaccine
3. No practical chemotherapy
4. Affect young
5. Affect underprivileged
1. Presence of a suitable host
2. Habits of the host
3. Escape from the host
4. Favorable conditions outside of host
5. Economic and social conditions
2. Mode of transmission
3. Susceptible host
1.Source of infection 2. Route of transmission 3. Susceptible people
secretion food, water, finger skin or wound
blood direct or indirect contact mucosa
focus of placenta
infection blood transfusion, injection,
insects sucking blood,
touch soil, water, grass
1. Clinical diagnosis
2. Laboratory diagnosis
1. Medical and surgical
3. Adequate nutrition
1. Reduction in sources
3. Destruction and/or control of reservoir hosts and vector