Introduction to Medical Parasitology History, Definitions by 83xvc88F


      to Medical Parasitology
        History, Definitions
   Classification and Taxonomy
         Human Parasites
Doç.Dr.Hrisi Bahar

• Parasitology – science about
  parasitic animals and relationships
  with their hosts.
• Para + situ + logos = conversation
  about those living nearby us
  = parasitology.

The first written records of what
are almost certainly parasitic
infections come from a period of
Egyptian medicine from 3000 to
400 BC, particularly the Ebers
papyrus of 1500 BC discovered
at Thebes.
A.lumbricoides eggs have been found in
human coprolites from Peru dating from
2277 BC.
Larval nematodes,possibly hook
worms, have been found in fecal samples
dated to about 200 BC from the Colorado
 In 1910, Marc Armand Ruffer found
S.haematobium eggs in two Egyptian
mummies dating from the,1250 to 1000
A parasite, is an organism that lives on
or inside another organism to the
detriment of the host organism.

The parasite grows, feeds, or uses
shelter of the host organism (including the
host itself) contributing negatively to the
• Parasitism:
 A symbiotic relationship in which the
 symbiont (parasite) benefits at the expense
 of the host by living either within the host
 (endoparasite) or outside the host
        Types of parasitism

Obligate parasites:All or most of their life
 cycle are parasitic.

Temporary parasites:parasitic for limited
 period for either feeding or reproduction.
Facultative parasites:organisms are not
 parasitic but can live parasitic for a limited
Accidental parasites:normally free living
 organisms can survive within a host when
 they are accidentally taken.
    What is a Parasite Host?

The host is the organism that the parasite
lives in.

           *A definitive host
        * An intermediate host
           *A paratenic host
            *A reservoir host
A definitive host is an organism that the
adult, or sexually reproductive stage of
the parasite lives in.

  Ex: When a human has an adult beef
  tapeworm in the intestine producing
   eggs,he or she is a “definitive host”
• An intermediate host is an organism
 that hosts an immature parasitic stage, or
 a stage that reproduces asexually

   Ex:Human are “intermediate hosts” to
     malariae parasites which multiply
      in human liver and blood cells.
• Reservoir hosts, with respect to human
 parasites, are hosts that are infected with a
 parasite and keep it alive even if the parasite is
 wiped out in humans.
 “Reservoir hosts can spread the parasite and reintroduce it to
  human populations”.
●A paratenic host is an organism that is
 infected with a parasite and can pass it on
 to another host, but in which the parasite
 does not develop further.

A biological relationship in which (usually)
two species live in close proximity to each
other and interact regularly in such a way
as to benefit one or both of the organisms.
*Symbiosis may exist between two or more
individuals of the same species as well as
between two or more individuals
representing two different species
The three principal varieties
      of symbiosis are

       * parasitism.
Mutualism is any relationship between two species of
organisms that benefits both species

A symbiotic relationship in which one organism, the
commensal,benefits without causing any detriment to
the other organism which is the host.

A symbiotic relationship in which one organism, the
parasite,benefit at the expense of the other
organism,which is the host.
Other Parasitology Definitions

*A cyst is a stage of many protozoan
 parasites that survives well in the
 environment. Cysts of human
 parasites are infective to humans.
*A trophozoite is a moving, feeding,
and multiplying stage of protozoan
life cycles. There are not male and
female trophozoites: they multiply
Other Parasitology Definitions

• Infective (=invasive) stage The stage
  of the parasite that invades the host .
• Vector:An Arthropod which is carrying
  and transferring parasites from one host
  to an other
   (Egg-larval stages-adult parasite-eggs)
 Other Parasitology Definitions

• Reservoir= Non-human “host” where the
  parasite can live.This term is only applied
  when the parasite can infect humans .
• Life Cycle= Stages of development of a
Essential features of the

*Parasite is smaller then the host
*Parasite has a shorter life span than
 it’s host
*Parasite has a greater reproductive
 potential than it’s host
Classification of parasites
  Zoological Classification
             Living organisms

   Without cell         With celular
   construction         construction

    Procaryotic cell        Eucaryotic cell
    (= monera)         (=protista /single cell)

       RICKETSIA                  PROTOZOA
         BACTERIA                (=metazoa)
   Ecological Classification

Endoparasite:a parasite that inhabits the
   internal organs or tissues of an animal
                or plant

 Ectoparasite:any parasite that lives on
     the outer surface of an animal.
Different location of parasites
into the host body
• Living in digestive system - coelozoic
  parasites (tapeworms)

• Living in tissues – histozoic parasites

●Living in blood – hemoparasites (Malaria etc.).
Methods of invasion and escape

 - Via vectors
 - Oral
- Penetration from the skin

•   Sputum
•   Via vectors
•   Faeces or urine
Pathologic effects of parasites

• Physical trauma (skin,mucosa)
• Migration
• Nutrition
• Toxins
• Immunosupression
Diagnosis of Parasitic Infections:

• 1. Clinical diagnosis
• 2. Laboratory diagnosis
Methods for study and
clinical analysis

• Parasitological analysis:
  tissue samples, excrements, surgical
  methods (biopsy)…
● Radiological (Rontgenoscopy Tomography ...)
• Serodiagnosis (Immunodiagnostics. ELISA test etc)
Major Groups of Parasites

•   -- Single-celled eukaryotes
•   – Malaria, Giardia, Trichomonas vaginalis
•   HELMINTS (The Worms)
•   – Multicellular animals
•   – Flukes, Tapeworms, Roundworms
•   – Multicellular animals
•   – Live outside the host
•   – Ticks, Lice, Fleas
Treatment of Parasitic Infections:

• 1. Medical and surgical
• 2. Chemotherapy
• 3. Adequate nutrition
Prevention and Control:

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

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