DISEASE GEOGRAPHICAL DISTRIBUTION EPIDEMIOLOGY MORPHOLOGY LIFE CYCLE OF THE PARASITE SYMPTOMS OF INFECTION DIAGNOSIS PREVENTION AND TREATMENT

1. A
PRESENTATION
ON
1
ENTAMOEBA
HISTOLYTICA
(AMOEBIASIS)

2. CONTENT
 INTRODUCTION
 DISEASE
 GEOGRAPHICAL DISTRIBUTION
 EPIDEMIOLOGY
 MORPHOLOGY
 LIFE CYCLE OF THE PARASITE
 SYMPTOMS OF INFECTION
 DIAGNOSIS
 PREVENTION AND TREATMENT
 REFERENCE
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3. INTRODUCTION
 Entamoeba histolytica is an anaerobic
unicellular parasitic protozoan, part of the
genus Entamoeba.
Predominantly infecting humans and other
primates causing amoebiasis, E. histolytica is
estimated to infect about 35-50 million people
worldwide.
Infection with E. histolytica maybe the cause of
a variety of symptoms, beginning from no
symptoms to severe fulminating intestinal
and/or life-threatening extraintestinal disease.
There are at least six species of the genus
Entamoeba that can be identified in human
stools. These are E. histolytica, E. dispar, E.
mshkoveskii, E. hartmanii, E. polecki, and E. coli.
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4. DISEASE
Entamoeba histolytica is the causative agent of
Amoebic dysentery or Amoebiasis.
Dysentery affects the intestines that results in
intense diarrhea with blood and is often
accompanied by pain and fever.
E. histolytica, as its name suggests (histo–lytic
= tissue destroying), is pathogenic.
Infection with E. histolytica may be;
- Asymptomatic (no symptoms)
- Intestinal Amoebiasis or
- Extraintestinal Amoebiasis
(Amoebic liver abscess).
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5. GEOGRAPHICAL DISTRIBUTION
Pathogenic Entamoeba
species occur worldwide. The
majority of amoebiasis cases
occur in developing countries,
more common in areas or
countries with poor sanitation,
particularly in the tropics.
3rd most common parasitic
death - India, China, Africa,
South America - 2-60%
prevalence.
It varies depending on
sanitation and climate.
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6. EPIDEMIOLOGY
Prevalence of infection with E. histolytica varies
greatly depending on region and
socioeconomic status. Amebiasis is endemic to
Africa, Latin America, India, and Southeast Asia.
It is estimated that infection with E. histolytica
leads to 50 million cases of symptomatic
disease and 40,000-110,000 deaths annually.
Amebiasis is the 3rd leading parasitic cause of
death worldwide. • Prospective studies have
shown that 4-10% of individuals infected with
E. histolytica develop amebic colitis and that
<1% of infected individuals develop
disseminated disease, including amebic liver
abscess.
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7. MORPHOLOGY
There are two stages in the life form :
1. actively growing and feeding stage referred to
as the Trophozoite form.
2. transmission stage called the Cyst form
(a) Trophozoite – actively motile feeding stage.
(b) Cyst – resistant, infective stage.
(a) Trophozoite
 vary in size from about 10-60μm in diameter.
 The cell body is divisible into two distinct
portions—Ectoplasm and Endoplasm. The
ectoplasm is clear and translucent while the
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8. MORPHOLOGY CONT.
 the endoplasm is granular. The endoplasm
often contains ingested red blood corpuscles.
The pseudopodia may be long, finger-like or
rounded in shape. The nucleus is indistinct in
living condition but in stained preparation it
shows a central Karyosome or Endosome.
 The nucleus is 4-6μm in diameter.
(b) Cyst
 Cysts range in size from 10-20μm. The cysts
are spherical. The cyst wall is double and the
cytoplasm usually bears four nuclei
(quadrinucleate). The immature cyst has
inclusions namely; glycogen mass and
chromatid bars. As the cyst matures, the
glycogen completely disappears.
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9. LIFE CYCLE OF PARASITE
 Infection by Entamoeba histolytica
occurs by the ingestion of mature
quadrinucleate cysts in fecally
contaminated food, water, or hands.
 The quadrinucleate cyst is resistant to
the gastric environment and passes
unaltered through the stomach.
 When the cyst of E.histolytica reaches
caecum or lower part of ileum,
excystation occurs and an amoeba with
four nuclei emerges and that divides by
binary fission to form eight
trophozoites.
 Trophozoites migrate to the large
intestine and lodge into the
submucosal tissue.
 Trophozoites grow and multiply by
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10. LIFE CYCLE CONT.
 phase of the life cycle is responsible for
producing characteristics lesion of
amoebiasis).
 Certain numbers of trophozoites are
discharged into the lumen of the bowel and
are transformed into cystic forms.
 The cysts thus formed are unable to
develop in the same host and therefore
necessitate a transference to another
susceptible host. The cysts are passed in the
feces.
 Because of the protection conferred by
their walls, the cysts can survive days to
weeks in the external environment. Cysts
are not highly resistant and are readily
killed by boiling. Trophozoites can also be
passed in diarrheal stools, but are rapidly
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11. SYMPTOMS
 Acute Intestinal Amoebiasis: dysentery (i.e.
bloody, mucus containing diarrhoea), lower
abdominal discomfort, flatulence.
 Chronic amoebiasis: low-grade symptoms such
as occasional diarrhoea, weight loss, and
fatigue also occurs.
 Amoebic abscess of the liver is characterized
by weight loss, fever, and a tender enlarged
liver and right upper quadrant pain.
 Roughly 90% of infected individuals have
asymptomatic infection but they may be
carriers.
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12. DIAGNOSIS
Microscopic examination of Stool samples:
Trophozoites may be seen in a fresh fecal
smear and cysts in an ordinary stool sample.
Serological Tests: useful for the diagnosis of
invasive amebiasis, detect anti-amoebic
antibodies in invasive amoebiasis, CIE, Gel
diffusion precipitation, Indirect
immunofluorescence.
 Imaging MRI and ultra-sonography, CT scans
detect abscess in the liver.
 Liver Aspiration Aspirations from the amoebic
liver abscess to detect trophozoites by wet
mount.
 Detection of the nucleic acid of this protozoan
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13. PREVENTION AND TREATMENT
PREVENTION
 Filtration and boiling of drinking water as the
cyst is resistant to chlorination.
 Education about the routes of transmission.
 Avoid eating raw vegetables grown by
sewerage irrigation and night soil.
 Proper disposal of sewage prevent
transmission Good personal hygiene.
 Washing of fruits & vegetables before
consumption.
 Protection of food from flies & cockroaches.
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14. PREVENTION AND TREATMENT
TREATMENT
 Intestinal infection: Usually nitroimidazole
derivatives are used because they are highly
effective against the trophozoite form of the
amoeba.
 Liver abscess: metronidazole and chloroquine.
Along with agents which act on the lumen of
the intestine to prevent re-invasion.
 Asymptomatic patients: For asymptomatic
patients, non endemic areas should be treated
by paromomycin. Other treatments include
diloxanide furoate and iodoquinol.
Paromomycin has a higher cure rate.
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15. REFERENCE
A. B. Ryan KJ, Ray CG, eds. (2004). Sherris
Medical Microbiology (4th Ed.). McGraw Hill. pp.
733–8. ISBN 0-8385-8529-9.
"Amoebiasis" (PDF). Wkly. Epidemiol. Rec. 72
(14): 97–9. April 1997. PMID 9100475.
Ryan KJ, Ray CG, eds. (2004). Sherris Medical
Microbiology (4th ed.). McGraw Hill. pp. 733–8.
ISBN 978-0-8385-8529-0.
 Blessmann J, Tannich E (October 2002).
"Treatment of asymptomatic intestinal Entamoeba
histolytica infection". The New England Journal of
Medicine. 347 (17): 1384.
doi:10.1056/NEJM200210243471722. PMID
12397207
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