Introduction pdf - د. صادق

Parasitology

Prof.Dr . Sadiq Al- Shaikh . Lec : 1

Introduction

Parasitology

: The branch of Biology which deals with the study of parasites .

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The parasites

: An organism which lives in or on the extent ( host ) of another

organism .

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The host

: The organism which harbours the parasite .

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Parasitism :

Is an association between 2 organisms in which one of them get the benefit

From the other ( the host ) and harming it , in different condition .

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Symbioses :

Is an association between 2 organisms in which they remain symbiotic all

the life , and each one of them get the benefit from the other , and no one

of them can live without the help of the other .

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commensalism :

Is an association between 2 organisms in which one of them gets

the benefit from the other without harming him .

Ex : Entamoeba coli .

Types of hosts :

1\ Definitive hosts ( final host ) :

The host which harbours the adult stage or the sexual stage of parasite .

Ex : man in case of Taenia .

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2 \ intermediate host :

The host which harbours the larval stage or the sexual stage of a parasite .

Ex : Snail in case of Bilharzia .

القوقع

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3 \ Reservoir host : المضيف الخازن

The host which harbours the parasite and considered the source of human infection as :

Dog in case of kala – azar ( ) الحمى السوداءwhich is caused by the parasite ( Leishmania

donovani ) .

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4\ Accident host :

The host which harbours the parasite which is not normally found .

Ex : the Toxo cara ( dog nematode ) ) (الديدان الخيطيةin man .

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5 \ Temporary host :

The host which harbours the parasite for a short time .

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6\ natural host :

The host which is easly infected with the parasite .

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7 \ The vector :

) ( الناقل

Is an organism which belongs to the arthropods ) ( المفصلياتor insects ) تارشحلا (

Which transmit the parasite , bacteria , and viruses from one host to another .

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Types of parasites :

1\ Endo parasites :

The parasite which lives inside the body of the host .

Ex : Entamoeba histolytica .

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2\ Ectoparasites :

The parasite which lives on the body of the host .

Ex : Lice ) . ( القمل

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3 \ Temporary parasite :

The organism which remains in parasitic state for a short time .

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4 \ Permenant parasite :

The organism which remains in parasitic state for whole its life .

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5 \ Facultatative parasite :

The parasite which can exist in parasitic or free living state .

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6 \ Obligatory parasite :

The parasite which cannot live only in a parasitic state .

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7 / Accidental parasite :

The parasite which infects an unusual host .

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8 / Coprozoic parasite : طفيلي برازي

the parasite which pass in the alimentary canal of the host without infecting it .

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9 / pseudo parasite :

In a stool examination the artifacts mistaken the parasites .

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10 / Aberrant parasite or wondering parasite :

The parasite which infects tissue or organ which is not normally found .

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Binomial nomenclature :

التس

مية الثنائية

Every organism ( parasite , bacteria and viruses ) is written by two names :

The 1

is genus name which starts by capital letter and the species name which starts by

small letter followed by the name of scientist who discovered the organism followed by
the year of discovery .

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Ascaris lambricoides, Linnaeus . 1758 .

Leishmania tropica , Borovsky 1898 .

Mycobacterium tuberculum , Kokh . 1882.

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Infection :

Is the establishment of parasite inside the body .

Infestation :

Is the establishment of parasite on the body in the skin .

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The science of parasitology includes the study of 3 important phyla :

1- Phylum protozoa : شعبة االبتدائيات

Science study protozoa logy .

2- Phylum helminthes : شعبة الديدان

Science study helminthology .

3- Phylum arthropoda :

Science study medical Entomology .

الحشرات الطبية

The parasite are classified according to the following system :

Phylum , class , order , family , genus ,and species .

Parasitology

Prof.Dr . Sadiq Al- Shaikh . Lec : 2

Protozoalogy : Is the science which studies the protozoa .

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protozoa : Are unicellular animals which can perform all the activities of life .

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The phylum protozoa is divided into 4 subphyla :

1- Subphylum sarcodina ( Rhizopoda ) : protozoa which moves by pseudopodia

these include all Amoebae .

2- Subphylum mastigophora

( حامل

) األوساط

: protozoa which moves by flagella

these include the flagellate .

3- Subphylum ciliate : protozoa which moves by cilia . these include paramecium .

4- Subphylum sporoza : protozoa without locomatic organells and they form

spores in one stage of life cycle .

The amoebae : most amoebae are free living and few are parasitic on man and
animals .

Ex : Entameaba histolica , Losh , 1875 .

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Intestinal parasite of man which cause intestinal and extra intestinal amoebiosis

The parasite localized in secum and large intestine it’s found in free stage .

1- The Trophozoite

Is vegative or active form of parasite .

The cytoplasm is divided into 2

parts :-

a- The ectoplasm is transparent and hyaline which filled the pseudopodium and form

1/3 of the size of cell .

b- The endoplasm is granular which form 2/3 of the size of the cell and certain nucleus

and ingested RBCs.

The nucleus contain central karyosome and evenly distributed kromatin granules .

On the inner site of nuclear membrane . the size ranges from 15 – 40 micro in diameter .

The Trophozoite found in the region of colon and in the tissue in extra intestinal
amoebiosis .

2- The precyst :

            This found in the lumen of the colon . The Trophozoite become
surrounded by blund pseudopodia and glycogen vaclue   or mass . some times
present in the precyst  , after development precyst thes form in the luman of the
colon .

3- The cyst :

Is usually rounded measuring from 10 – 25 micron .

Contain either one , two or four nuelei with central karyosame .in the cytoplasm there
are one or more chromatoidal bars with rounded ends . the cyst forms in the lumen of the
colon .

The size of the cyst depend on the parasite race .

if less than 10 micron we call it Entamaeba hartmanni .

if more than 10 m we call it E . histolytica which is the pathogemic one .

There is another race Entameaba dispar . this amoeba and E . hartmanni is rarely
pathogenic .

Life cycle

Man gets infection by ingestion contaminated food or drink with the cyst of parasite . the
cyst pass through the stomach and small intestine ingested by digested juice in the secum
and the colon where the medium is alkaline existation occur and form each four nucleated
cyst eight small amoebullae form with active movement and invate the mucous membrane
of the colon and by secretion of protolytic enzyme ( histolysin ) which disolve the mucous
membrane and muscularis mucosa forming in the intestinal lesion .

The lesion are distributed all over the colon at the end of the colon the cyst form and pass
out the body with feces and if the sanitary conditions

(

ظروف

) صحية

is not good

contamination of food especially vegetables either by human contention or flies and the
cyst can survive in humid weather for 10 days and by this time can infiect other healthy
person .

Pathogenicity virulence

It is the capacity of the parasite to produce lesion or lesion in the host .

There are 3 theories which explains the Pathogenicity of E . histolytica .

1- It is the state that E . histolytica are 2 types :

Virulence

or pathogenic which produce lesion in the host .

A virulent which cannot produce lesion .

2- It is the state that all strains of E . histolytica are virulent and appearance of the

symptoms in the host depend on the immunity of the host .

3- It is the state that the amoeba strain are A virulent for production of lesion .

It requires some Bacteria to become Pathogenic .