2. SYNOPSIS
1. INTRODUCTION
2. ENTAMOEBA HISTOLYTICA â
⢠Morphology
⢠Life cycle
⢠Pathogenicity
⢠Treatment
⢠Control
3. TRYPANOSOMA GAMBIENSE â
⢠Morphology
⢠Life cycle
⢠Pathogenicity
⢠Treatment
⢠Control
4. CONCLUSION
5. REFERENCES
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3. 1.INTRODUCTION
⢠PROTOZOA â
â˘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 .
â˘Many protozoa alternate between a free living vegetative
from known as astrophozoite and a resting form called a cyst .
â˘Most protozoa have a single nucleus .
â˘Protozoa are heterotrophic microorganism .
â˘Many protozoal species move independently by one of three
types of loco motor organelles: flagella, cilia, and
pseudopodia .
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4. 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.
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5. ⢠MORPHOLOGY â
There are 3 phases in the life cycle of E. histolytica â
1) TROPHOZOITE ( Growing or feeding stage )-
Shape â not fixed
Size â 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 â shape is spherical
size is 4-6 um
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6. 2) PRE- CYSTIC STAGE -
Size â 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 â STAGE â
Size â 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
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8. ⢠LIFE â CYCLE â
ďIt passes its life cycle only in 1 host-man.
ďInfective stage : mature quadrinucleate cyst passed in
feces of carrier and convalescent. The cyst can remain viable
under moist condition for 10 days .
ďMode of transmission : man acquires infection by
swallowing food and water contaminated with cysts.
ďAs the cyst wall is resistant to action of gastric juice , the
cyst enters the small intestine undamaged.
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9. ďWhen the cyst reaches caecum and lower part of the
ileum ,due to the alkaline medium , the cyst wall
damaged by trypsin leading to excystation.
ďThe 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 .
ďThe nuclei in the metacyst immediately undergoes
division to form 8 nuclei , each gets surrounded by its
own cytoplasm forming metacyst trophozoites.
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10. Life cycle of Entamoeba histolytica
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11. ⢠PATHOGENECITY-
ďIncubation period â 4-5 days.
ďSymptomatology â 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.
ďAMOEBIC 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.
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12. ďDysentery is a symptom characteristics of extensive
intestinal ulcerations representing only a part of the
clinical picture of intestinal amoebiasis.
ďClinical picture vary from acute colitis to chronic colitis
and asymptomatic carrier state.
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13. ⢠TREATMENT â
Three classes of drugs are used :
ďLuminal amoebicides â iodoquinol , paromomycin and
tetracycline act in the intestinal lumen but not in tissue.
ďTissue amoebicides â chloroquine is affective in systemic
infection but less effective in the intestine.
ďBoth luminal and tissue amoebicides â metronidazole and
related compounds act on both sites and are the drug of
choice for treating amoebic colitis and amoebic liver
abscess.
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14. ⢠CONTROL â
ďWash hands thoroughly with soap and hot running water for
at least 10 sec. after using toilet or changing a babyâs diaper
and before handling food .
ď Clean bathrooms and toilet ; pay particular attention to
toilet seats and taps .
ďAvoid sharing towels or face wash .
â˘TO HELP PREVENT INFECTION-
ďBoil water or treat with iodine tablets .
ďAvoid eating street foods especially in public where other are
sharing sauces in one container .
ďAvoid raw vegetables.
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15. 3.TRYPANOSOMA GAMBIENSE
ďTrypanosoma gambiense is a protozoan haemoflagellate
endoparasite of man inhabiting the blood , lymph and the
intercellular spaces of different tissues and organs of man .
ď Hogs , goat, cattle and sheep are potential reservoir
hosts.
ďThe parasite causes a disease called Gambian or West-
African sleeping sickness in human beings.
â˘GEOGRAPHICAL DISTRIBUTION â
ďT. gambiense are found in West and Central Africa .
ďTheir distribution depends upon the areas where the
vector of the parasite, Glossina palpalis actually exists .
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16. ⢠HABITAT â
ďT. 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 â
Shape and size :
ďT. gambiense has a slender elongated , colorless , sickle â
shaped and flattened microscopic body which is tapering at
both the ends .
ďAnterior end is pointed and posterior end is blunt .
ďBody length varies from 15-30 micron and width from 1-3
micron .
ďThe shape and size of its body vary with the form in which it
exists .
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17. Pellicle and undulating membrane :
ďThe body is covered by a thin , elastic and firm pellicle .
ďIt maintains the general shape of the body .
ďThe pellicle is made up of fine fibril .
Flagellum :
ďFlagellum is single in Trypanosoma , i.e. , it is uniflagellate .
ďThe flagellum arises from the basal granule situated near the
posterior end of the body.
Kinetoplast :
ďJust posterior to basal granule , there is a small , spherical or
disc- shaped parabasal body or kinetoplast .
ďKinetoplast contains extra- nuclear DNA and hence, it is self â
duplicating body .
ďThe kinetoplast is related to locomotion .
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18. Cytoplasm :
ďIts cytoplasm is differentiated into ectoplasm and
endoplasm .
ďThe cytoplasm contains numerous granules called volutin
granules .
ďCytoplasm also contains Golgi apparatus , mitochondria ,
ER and nucleus .
Nucleus :
ďA single , oval or spherical and vesicular nucleus
(trophonucleus) is seen in the middle of its body .
ďThe nucleus contains a large endosome surrounded by
chromatin.
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20. Polymorphic forms of T. gambiense:
1. Leishmanial (amastigote ) â
⢠Small , oval surrounded body .
⢠Flagellum reduced , fiber âlike 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 .
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21. 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 .
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22. ⢠LIFE CYCLE -
ďThe 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.
ďT. gambiense lives harmlessly in the blood of antelopes
ďPart of life cycle in man : When an infected fly bites a man , it
inoculates a few parasites in the blood of man .
ďThe parasites first live in the blood of infected man but later
find their way into the cerebrospinal fluid .
ďThe parasites multiply by longitudinal binary fission in the
blood and produce three form of individual=
(1) Long and thin formâs with a free flagellum ,
(2) Short and stumpy form with a reduced flagellum and
(3) Intermediate forms.
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23. ďWhen 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 .
ďThese parasites remain in the midgut of fly for a few days
and start multiplying by longitudinal binary fission.
ďAfter 10-15 days , long slender forms appear in great
number which move forward to the proventriculus .
ďAfter several more days, the trypanosomes make their way
to the flyâs salivary gland .
ďThese short and stumpy forms are capable of development
in the intermediate host , Glossina palpalis .
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24. ďHere the development continues for 2-5 days and the
crithidial forms produce METACYCLIC FORM (TRYPANOSOME
FORM )which are now infective .
ďWhen the fly bites a man , the metacyclic forms enter the
blood of man along with the saliva of the fly .
ďThe whole cycle in the fly usually takes 2-30 days .
ďIn the salivary glands they multiply by longitudinal binary
fission and develop into crithidial forms(short flagellum and
undulating membrane .
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25. Life cycle of Trypanosoma gambiense
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26. ⢠PATHOGENICITY-
ďThe bite of an infected fly is usually followed by itching
and irritation near the wound .
ďIn blood the parasite multiplies and absorbs nutrient from
it .After few days fever , headache ,weakness ,loss of weight
and anaemia occur.
ďUsually the parasites succeed in penetrating the lymphatic
glands .
ďBecause of its infection , the lymphatic glands swell and
after it the parasites enter the cerebrospinal fluid and brain
causing a sleeping sickness like condition.
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27. â˘TREATMENT -
ďIn early infection drugs like suramin (Bayer 205 )and
pentamidine are used .
ďIn later stage when central nervous system is involved
arsenicals like tryparsamide , melarsen and tnmelarsen are
being
used.
ďNitrofurazone (fiiracin) may be used in certain cases .
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28. ⢠CONTROL-
ďControl breeding sites .
ďInsecticides
ďTreatment of human cases
ďGeneral cleanliness
ďProtection against bites
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29. 4. CONCLUSION
ďEntamoeba histolytica is an anaerobic parasitic amoebozoan
, part of the genus Entamoeba .
ďPredominantly infecting humans and other primates causing
amoebiasis .
ďE. histolytica is estimated to infect about 50 million people
worldwide .
ďTrypanosoma gambiense is a protozoan haemoflagellate
endoparasite of man inhabiting the blood , lymph and the
intercellular spaces of different tissues and organs of man.
ďThe parasite causes a disease called Gambian or West-
African sleeping sickness in human beings.
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