Human parasitology

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Human Parasitology
Shandong University Department of Parasitology He
Shenyi (??? ) MD, Ph.D. Professor
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Introduction to Human Parasitology

• Concept of Human Parasitology
• The Scope of Human Parasitology
• Terms of Parasitology
• Parasites Harms to Man
• Human Immunity against Parasites
• Characteristics of parasitic diseases

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Human parasitology

• Human parasitology is the study of those
  organisms which parasitise humans.  According to
  the very broad definition of parasitology,
  parasites should include the viruses, bacteria,
  fungi, protozoa and metazoa (multi-celled
  organisms) which infect their host species. 
  However, for historical reasons the first three
  have been incorporated into the discipline of
  Microbiology. 

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2. The Scope of Human Parasitology

• 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.

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• Class Lobosea
• Class Zoomastigophorea
• Class Sporozoa
• Class Ciliophora

Medical Protozoology

• Human Parasitology

• Class Nematoda
• Class Trematoda
• Class Cestoda
• Class Metacanthocephala

Medical Helminthology

• Class Insecta
• Class Arachnida
• Class Crustacea
• Class Chilopoda

Medical Arthropodology
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Class Lobosea
Entamoeba histolytica Non-pathogenic amoeba
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Class Zoomastigophorea

• Leishmania sp

Trichomonas vaginalis
Giardia
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Class Sporozoa

• Plasmodium spp

Toxopasma gondii Cryptosporidium Pneumocycstis
carinii
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Class Ciliophora

• Balantidium coli

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Class Nematoda

• Ascaris lumbricoides

Trichuris trichiura Hookworm Enterobius
vermicularis Filaria Trichinella spiralis
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Nematoda
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Class Trematoda

• Clonorchis sinensis

Fasciolopsis buski Paragonimus westermani
Schistosoma japonicum
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Trematoda
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Class Cestoda

• Taenia solium

Taenia saginata Echinococcus granulosus
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Cestoda
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Class Metacanthocephala
Macracanthorhynchus

hirudinaceus
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Class Insecta

• Anopheles sinensis

Lucilia sericata
Lice Sandflies , Fleas
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Class Arachnida
Ticks Mites

• Sarcopes scabiei

follicle mite
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Class Crustacea

• Cambaroides
• Potamon  

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Class Chilopoda
centipede
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4. Terms of Parasitology

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Symbiosis

• (1)Symbiosis(????)Two different organisms live
  together and interact, in this association one
  partner lives in or on another ones body.
  including 3 typesMutualism, Commensalism,
  Parasitism.

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Symbiosis

• (2)Mutualism(????)is a permanent association
  between two different organisms that life apart
  is impossible, two partners benefit each other,
  such as termites and flagellates.
• The mutuals are metabolically dependent on one
  another one cannot survive in the absence of the
  other.

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Symbiosis

• (3) Commensalism(???????)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(????)is the association of two
  different organisms, in which one partner is
  benefited while the other is injured, such as
  Ascaris lumbricoides and man.

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Parasite

• (5) Parasite(???) 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.

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Parasite

• endoparasite
• ectoparasite
• temporary parasite
• permanent parasite
• obligatory parasite
• facultative parasite
• accidental parasite
• opportunistic parasite

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Endoparasite
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Ectoparasite
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Host

• (6) Host(??) In parasitism, it supplies the
  parasite with nourishment and shelter, it is the
  injured partner.
• (7) Carrier(???) A person who harbours parasite
  has no clinical symptoms, is an important source
  of infection in epidemiology.

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• (8) Definitive (final) host(???)harbours adult or
  sexually reproductive stage of a parasite.
• (9) Intermediate host(????)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.

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• (10) Reservoir hosts(????)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.

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Zoonosis

• (11) Zoonosis(?????)refers to animals diseases
  which can be transmitted to man. (These animals
  infected with parasites are called reservoir
  hosts.)

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• (12) Paratenic host or transport host(????)is an
  abnormal host in which some parasitic larvae can
  survive but cant develop into adults. If the
  larvae have a chance to enter their appropriate
  hosts, they can continue to develop into adults
  there.

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• (13)  Larva migrans(?????)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.

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Life cycle

• (14) Life cycle(???) is the process of a
  parasites growth, development and reproduction,
  which proceeds in one or more different hosts
  depending on the species of parasites.
• (15)Infective Stage(???)is a stage when a
  parasite can invade human body and live in it .

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Life cycle

• (16) Infective Route(????)is the specific
  entrance through which the parasite invades the
  human body.
• (17) Infective Mode(????) 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.

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Life cycle

• (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.

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• (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.

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• (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.

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Evolution of Parasitism

• endoparasite Free living
  
• ectoparasite
  Commensalism(????)
• temporary parasite Symbiosis
  Mutualism(????)
• permanent parasite
  Parasitism
• obligatory parasite
  carrier
• facultative parasite
  parasite Host
• accidental parasite
  Patient
• opportunistic parasite
  
• Final host Intermediate host Reservoir
  host Paratenic host
• 
  Zoonosis Larva migrans

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4. Parasites Harms to Man

• Mechanical effects of parasites on host
  tissues and organs e. g. , biliary ascariasis
  and larva migrans.
• Depriving nourishment from hosts e.g.
  hookworms suck blood.
• Toxic effect e. g., mosquitoes, spiders
  and ticks introduce venom when they insert their
  mouth parts into the skin.
• Immuno-pathological lesion e.g. schistosoma
  liver cirrhosis when hydatid fluid is released
  from the rupture of a hydatid cyst anaphylaxis
  often results.

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5. Human Immunity against Parasites

• Its intensity and specificity are usually at a
  lower level than those produced by bacteria and
  viruses. It refers to Non-sterilizing immunity
  (Premunition????Concomitant immunity????). The
  host may be protected from superinfection????as
  long as the parasites remain in the body. This
  situation is known as premunition(????). This may
  be of great importance in endemic areas in
  limiting the severity of infection with
  Plasmodium, Schistosome , hookworms and other
  parasites.

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(WHO) - Priority Diseases

• 1. Schistosomiasis
• 2. Malaria
• 3. Filariasis
• 4. Trypanosomiasis
• 5. Leishmaniasis
• 6. Leprosy (replaced by HIV/AIDS)

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Why were they selected?

• Schistosomiasis - 200,000,000 infected
• 500,000-1,000,000 deaths/year
• Malaria - 500,000,000 infected
• 2,500,000 deaths/year
• Filariasis - 250,000,000 infected
• Trypanosomiasis - 25,000,000 infected
• 65,000 deaths/year
• Leishmaniasis - 1,200,000 infected
• Leprosy - 1,300,000 infected
• Approximately 25 of world's population infected
  by one of these.

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General Characteristics

• 1. Chronic diseases
• 2. No effective vaccine
• 3. No practical chemotherapy
• 4. Affect young
• 5. Affect underprivileged
• 6. Vector-borne

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Geographic Distribution Factors (Endemicity)

• 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

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Presence of Diseases in a Population
(Prevalence)

• Factors required
• 1. Source
• infected persons
• carriers
• animals

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Presence of Diseases in a Population
(Prevalence)

• 2. Mode of transmission
• direct
• indirect
• vectors
• 3. Susceptible host
• immunity

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• Three key links of disease transmission
• 1.Source of infection 2. Route of transmission
  3. Susceptible people
• excrement
  mouth
• secretion food, water, finger
  skin or wound
• blood direct or indirect contact
  mucosa
• focus of
  placenta
• infection blood transfusion, injection,
  
• intermediate host,
  
• insects sucking blood,
• congenital ,
• touch soil, water, grass

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Diagnosis of Parasitic Infections

• 1. Clinical diagnosis
• 2. Laboratory diagnosis

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Treatment of Parasitic Infections

• 1. Medical and surgical
• 2. Chemotherapy
• 3. Adequate nutrition

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Prevention and Control

• 1. Reduction in sources
• 2. Education
• 3. Destruction and/or control of reservoir hosts
  and vector