Parasitology

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Parasitology
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Introduction
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• Parasitology-
• It is the science that deals with organisms
  that live on or within other organisms (Hosts).
• Mainly in this course branch we study the
  parasites which live on the expense of man.

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• The relationship between two living organisms
  may be one of the following-

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• ? Mutualism-
• Mutual benefits is derived from the
  association of these two organisms
• Benefit Benefit

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• ?Symbiosis
• Mutual benefit , and the two organisms can not
  live independently (physiological relationship).
• Benefit Benefit

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• ?Commensalisms-
• One partner benefits (commensal) while the
  other (host) is unaffected. It may be
  called a non-pathogenic parasite.
• Benefit No harm ,No benefit

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• ?Parasitism-
• One organism (parasite) lives at the expense of
  the other (host) which usually suffer from the
  association. It is called a pathogenic parasite.
• Benefit Harm

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Parasitism
Host
Parasite
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Types of Parasites
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• Ectoparasite-
• Live outside the body of the host
  (infestation). e.g. Lice
• Endoparasite-
• Live inside the host (infection).
• e.g. most of human parasite

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• Facultative Parasite-
• Capable of leading both a free-living and a
  parasitic existence (live parasitically or none
  parasitically).
• Obligate Parasite-
• Completely dependent upon its host and can not
  lead a free life.

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• Temporary Parasite-
• Parasitic only during part of its life cycle.
• Permanent Parasite-
• Live parasitically during the whole life cycle.

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• Incidental Parasite-
• Can establish itself in a host in which it
  does not ordinary live
  (occur in abnormal host).
• Pseudoparasite-
• A certificate mistaken as a parasite.

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• Specific Parasite-
• Occurs in one particular host.
• Pathogenic Parasite-
• Causing injury to the host.

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• Coprozoic Parasite- copro faeces
• Parasite passes the alimentary canal without
  infection or contaminant faeces after release.

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Types of Hosts
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• Definitive Host (final or terminal)-
• Harbours the adult or mature parasite.
• In which parasite can reproduce sexually if it
  applicable.

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Definitive Host
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• Main Host-
• In which the parasite occur more frequently
  and reach maturity.
• Secondary Host-
• In which the parasite occur less frequently
  and growth is retarded.

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• Accidental Host-
• In which its occurrence and development is
  very difficult.

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• Intermediate Host-
• Harbours the immature stage of the parasite
  (larval stage) that reproduce asexually into
  infective stage.
• Reservoir Host-
• Animal that harbours the same species of
  parasites as man and constitute a source of
  infection to him.

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Factors Affecting Prevalence Geographical
Distribution of the Parasites
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1. Availability of suitable hosts and their habits.
2. Immune status of the hosts.
3. Easy entry exit of the parasite to
   and from the host.
4. Regional habits.
5. Socio-economical status.

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• Education
• knowledge about parasites reduce the
  infections rates
• Environmental sanitation
• water, food, waste disposal,..
• Suitability of the environmental and climatic
  conditions.

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• Control of intermediate hosts, treatment of
  infected cases.ect.
• Nature of life cycle e.g. parasites with simple
  life cycles have more distribution than with
  complicated cycles.

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General Modes of Parasites Transmission
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1. Congenital (through placenta) e.g.
   malaria
2. Direct Contact. e.g. arthropods, Leshmania,
   Tichomonas Entamoeba gingivalis .
3. Indirect contact (in contaminated objects).
   e.g. amoebic cyst, helminthes egg as of H. nana
   , Taenia , Entrobius.

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• In food as most parasites are intestinal and
  their infective stage reach food either
• In flesh e.g. T. saginata T. solium.
• In contaminated water e.g. vegetable with
  protozoa cyst helminthes egg.
• Contamination by insects
  e.g. mechanically by housefly.
• Contamination by food handler.

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• In water drinking contaminated water with
  protozoa cyst or helminthes egg or using water
  containing the intermediate host, infective stage
  e.g. Schistosomiasis.
• Contaminated soil e.g. Ancylostoma.
• Animals e.g. dog worm (dog), Toxoplasmosis
  (cat)

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• Arthropods
• - Transmission occurs either-
• Mechanically e.g. faecal cyst eggs to food by
  house fly.
• Biologically e.g. malaria filariasis
  ( by mosquitoes), sleeping sickness (by
  Tsetse fly) Leishmaniasis
  (by sand fly)

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• Praziquantel is very safe, taken as a single or
  divided dose according to the worm type.
• Dose is calculated according to the patient
  weight.
• Praziquantel is swallowed, not chewed as it is
  very bitter in taste.