Protozoan disease

TOPIC :- PROTOZOAN PARASITES
• ENTAMOEBA HISTOLYTICA
• TRYPANOSOMA GAMBIENSE
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SYNOPSIS
1. INTRODUCTION
2. ENTAMOEBA HISTOLYTICA –
• Morphology
• Life cycle
• Pathogenicity
• Treatment
• Control
3. TRYPANOSOMA GAMBIENSE –
• Morphology
• Life cycle
• Pathogenicity
• Treatment
• Control
4. CONCLUSION
5. REFERENCES

1.INTRODUCTION
• PROTOZOA –
•Protozoa is an informal term for single celled eukaryotic ,
either free- living or parasitic, which feed on organic matter.
• Protozoa vary substantially in size and shape .
•Many protozoa alternate between a free living vegetative
from known as astrophozoite and a resting form called a cyst .
•Most protozoa have a single nucleus .
•Protozoa are heterotrophic microorganism .
•Many protozoal species move independently by one of three
types of loco motor organelles: flagella, cilia, and
pseudopodia .

2.ENTAMOEBA HISTOLYTICA
• GEOGRAPHICAL DISTRIBUTION - Worldwide .
More common in the tropics and subtropics than in the
temperate zone .
• HABITAT - Trophozoite of E. histolytica live in
the mucous and sub mucous layer of the large
intestine.

• MORPHOLOGY –
There are 3 phases in the life cycle of E. histolytica –
1) TROPHOZOITE ( Growing or feeding stage )-
Shape – not fixed
Size – range from 18-40 um
Cytoplasm- a clear translucent ectoplasm and a granular
endoplasm.
Red blood cells , occasionally leukocyte and tissue
debris are found inside the endoplasm.
Nucleus – shape is spherical
size is 4-6 um

2) PRE- CYSTIC STAGE -
Size – 10-20um
Shape- round or slightly ovoid with a blunt pseudopodium
projecting from the periphery.
Endoplasm is free of red blood cells and other food particles.
Nucleus structure is same as that of trophozoite .
3) CYSTIC – STAGE –
Size – the small race being 6-9 um and large race 12-15 um.
During encystment , the parasite become rounded and is
surrounded by a highly refractile membrane , called CYST wall.
Cytoplasm is clear and hyaline . In early stage of development
cytoplasm of cyst shows-
(a) Chromatid or Chromidial Bars
(b) Glycogen Mass

• LIFE – CYCLE –
It passes its life cycle only in 1 host-man.
Infective stage : mature quadrinucleate cyst passed in
feces of carrier and convalescent. The cyst can remain viable
under moist condition for 10 days .
Mode of transmission : man acquires infection by
swallowing food and water contaminated with cysts.
As the cyst wall is resistant to action of gastric juice , the
cyst enters the small intestine undamaged.

When the cyst reaches caecum and lower part of the
ileum ,due to the alkaline medium , the cyst wall
damaged by trypsin leading to excystation.
The cytoplasm gets detached from the cyst wall and
amoeboid movements appear causing a tear in the
cyst wall , through which quadrinucleate amoeba is
liberated . This stage is called the METACYST .
The nuclei in the metacyst immediately undergoes
division to form 8 nuclei , each gets surrounded by its
own cytoplasm forming metacyst trophozoites.

Life cycle of Entamoeba histolytica

• PATHOGENECITY-
Incubation period – 4-5 days.
Symptomatology – term AMOEBIASIS is used to denote all
those conditions which are produced in human host by
infection with E. histolytica at different areas of its invasion.
AMOEBIC DYSENTERY is a condition in which the infection is
confined to the intestinal canal and is characterized by the
passage of blood and mucus in the stool.

Dysentery is a symptom characteristics of extensive
intestinal ulcerations representing only a part of the
clinical picture of intestinal amoebiasis.
Clinical picture vary from acute colitis to chronic colitis
and asymptomatic carrier state.

• TREATMENT –
Three classes of drugs are used :
Luminal amoebicides – iodoquinol , paromomycin and
tetracycline act in the intestinal lumen but not in tissue.
Tissue amoebicides – chloroquine is affective in systemic
infection but less effective in the intestine.
Both luminal and tissue amoebicides – metronidazole and
related compounds act on both sites and are the drug of
choice for treating amoebic colitis and amoebic liver
abscess.

• CONTROL –
Wash hands thoroughly with soap and hot running water for
at least 10 sec. after using toilet or changing a baby’s diaper
and before handling food .
 Clean bathrooms and toilet ; pay particular attention to
toilet seats and taps .
Avoid sharing towels or face wash .
•TO HELP PREVENT INFECTION-
Boil water or treat with iodine tablets .
Avoid eating street foods especially in public where other are
sharing sauces in one container .
Avoid raw vegetables.

3.TRYPANOSOMA GAMBIENSE
Trypanosoma gambiense is a protozoan haemoflagellate
endoparasite of man inhabiting the blood , lymph and the
intercellular spaces of different tissues and organs of man .
 Hogs , goat, cattle and sheep are potential reservoir
hosts.
The parasite causes a disease called Gambian or West-
African sleeping sickness in human beings.
•GEOGRAPHICAL DISTRIBUTION –
T. gambiense are found in West and Central Africa .
Their distribution depends upon the areas where the
vector of the parasite, Glossina palpalis actually exists .

• HABITAT –
T. gambiense lives as a parasite in blood , lymph ,lymph
node , spleen , or cerebrospinal fluid of man and in the
intestine of blood sucking fly Glossina palpalis (Tsetse fly ).
• MORPHOLOGY –
Shape and size :
T. gambiense has a slender elongated , colorless , sickle –
shaped and flattened microscopic body which is tapering at
both the ends .
Anterior end is pointed and posterior end is blunt .
Body length varies from 15-30 micron and width from 1-3
micron .
The shape and size of its body vary with the form in which it
exists .

Pellicle and undulating membrane :
The body is covered by a thin , elastic and firm pellicle .
It maintains the general shape of the body .
The pellicle is made up of fine fibril .
Flagellum :
Flagellum is single in Trypanosoma , i.e. , it is uniflagellate .
The flagellum arises from the basal granule situated near the
posterior end of the body.
Kinetoplast :
Just posterior to basal granule , there is a small , spherical or
disc- shaped parabasal body or kinetoplast .
Kinetoplast contains extra- nuclear DNA and hence, it is self –
duplicating body .
The kinetoplast is related to locomotion .

Cytoplasm :
Its cytoplasm is differentiated into ectoplasm and
endoplasm .
The cytoplasm contains numerous granules called volutin
granules .
Cytoplasm also contains Golgi apparatus , mitochondria ,
ER and nucleus .
Nucleus :
A single , oval or spherical and vesicular nucleus
(trophonucleus) is seen in the middle of its body .
The nucleus contains a large endosome surrounded by
chromatin.

Polymorphic forms of T. gambiense:
1. Leishmanial (amastigote ) –
• Small , oval surrounded body .
• Flagellum reduced , fiber –like embedded in the
cytoplasm
• External flagellum is not found.
2. Leptomonad (promastigote):
• Elongated body .
• A free flagellum originated from the basal granule.
• No undulating membrane is formed .

3. Crithidial (epimastigote ):
• Short , elongated but stumpy body .
• A long flagellum arises from basal granule and become
free anteriorly .
• Undulating membrane ill- developed .
4. Trypanosome (trypomastigote):
• Elongated and slender body .
• Flagellum is large and become free anteriorly .
• Undulating membrane is well developed .

• LIFE CYCLE -
The life cycle of T. gambiense is completed within two hosts
i.e., digenetic ,a primary vertebrate (man) and secondary
invertebrate (Tsetse fly ) host or vector.
T. gambiense lives harmlessly in the blood of antelopes
Part of life cycle in man : When an infected fly bites a man , it
inoculates a few parasites in the blood of man .
The parasites first live in the blood of infected man but later
find their way into the cerebrospinal fluid .
The parasites multiply by longitudinal binary fission in the
blood and produce three form of individual=
(1) Long and thin form’s with a free flagellum ,
(2) Short and stumpy form with a reduced flagellum and
(3) Intermediate forms.

When a tsetse fly sucks the blood of an infected man , a
number of parasites enters into the midgut of the fly along
with the blood .
These parasites remain in the midgut of fly for a few days
and start multiplying by longitudinal binary fission.
After 10-15 days , long slender forms appear in great
number which move forward to the proventriculus .
After several more days, the trypanosomes make their way
to the fly’s salivary gland .
These short and stumpy forms are capable of development
in the intermediate host , Glossina palpalis .

Here the development continues for 2-5 days and the
crithidial forms produce METACYCLIC FORM (TRYPANOSOME
FORM )which are now infective .
When the fly bites a man , the metacyclic forms enter the
blood of man along with the saliva of the fly .
The whole cycle in the fly usually takes 2-30 days .
In the salivary glands they multiply by longitudinal binary
fission and develop into crithidial forms(short flagellum and
undulating membrane .

Life cycle of Trypanosoma gambiense

• PATHOGENICITY-
The bite of an infected fly is usually followed by itching
and irritation near the wound .
In blood the parasite multiplies and absorbs nutrient from
it .After few days fever , headache ,weakness ,loss of weight
and anaemia occur.
Usually the parasites succeed in penetrating the lymphatic
glands .
Because of its infection , the lymphatic glands swell and
after it the parasites enter the cerebrospinal fluid and brain
causing a sleeping sickness like condition.

•TREATMENT -
In early infection drugs like suramin (Bayer 205 )and
pentamidine are used .
In later stage when central nervous system is involved
arsenicals like tryparsamide , melarsen and tnmelarsen are
being
used.
Nitrofurazone (fiiracin) may be used in certain cases .

• CONTROL-
Control breeding sites .
Insecticides
Treatment of human cases
General cleanliness
Protection against bites

4. CONCLUSION
Entamoeba histolytica is an anaerobic parasitic amoebozoan
, part of the genus Entamoeba .
Predominantly infecting humans and other primates causing
amoebiasis .
E. histolytica is estimated to infect about 50 million people
worldwide .
Trypanosoma gambiense is a protozoan haemoflagellate
endoparasite of man inhabiting the blood , lymph and the
intercellular spaces of different tissues and organs of man.
The parasite causes a disease called Gambian or West-
African sleeping sickness in human beings.

Protozoan disease

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