Introduction to Parasitology

Introduction to Parasitology

—  The study of parasites is called parasitology.

—  Parasites:

-         eukaryotic, uni or multicellular organisms and most of them are motile.

-         takes its nourishment and other needs from a host.

—  Characteristics of parasites

•          Undergo simple to complex life cycle.

•          Often involve two hosts.

•          Alternates sexual and asexual reproduction.

•          Some are motile by flagella, cilia.

•           Performs all functions – reproduction, digestion, respiration & excretion.

—  (b) Parasitism

   The parasite derives benefit from the host and always causes injury to the host, however mild may be (Eg: Genus Plasmodium species causing malaria).

  The benefited partner in parasitism is the “Parasite”.

—  Obligate Parasite - This parasite is completely dependent on the host during a segment or all of its life cycle, e.g. Plasmodium spp.

—  Facultative parasite – an organism that exhibits both parasitic and non-parasitic modes of living and hence does not absolutely depend on the parasitic way of life, but is capable of adapting to it if placed on a host. E.g. Naegleria fowleri

—  Accidental parasite – when a parasite attacks an unnatural host and survives. E.g. Hymenolepis diminuta (rat tapeworm).

—  Aberrant parasite - is one that wanders in to an organ in which it is not usually found. E.g. Entamoeba histolytica in the liver or lung of humans.

   

—    (b) Ectoparasite:-

     

  The Parasite lives on the outer surface or in the superficial tissue of the host. Eg., Lice, ticks, mites etc.

   Vector transmitting pathogenic microorgani

 (b) Intermediate host:- 

     Harbors the larval or asexual stage of the parasite. (Eg: malarial parasites of man)