Amebiasis is caused by the protozoan Entamoeba histolytica and is a major public health problem globally. It is commonly found in developing tropical and subtropical countries where poverty, poor sanitation, and malnutrition are prevalent risk factors. E. histolytica infection may be asymptomatic or may cause intestinal disease ranging from mild diarrhea to severe colitis or extraintestinal infections such as amoebic liver abscess. Diagnosis involves identification of trophozoites or cysts in stool samples or detection of antibodies or antigens in blood tests. Treatment involves luminal agents such as metronidazole to eliminate active infections and tissue amoebicides such as diloxanide furoate to clear cyst

1. Amebiasis
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2. • Harboring(infection) of protozoa Entamoeba
histolytica inside the body with or without the
disease is called amoebiasis.
• Associated with high mortality and morbidity
• Major public health problem globally
• 2nd leading cause of death due to parasitic
disease ( 1st being malaria )

3. Epidemiology
• 10% of population infected globally
• About 100,000 deaths occur every year globally
• High prevalence in tropics and subtropics
• Risk factors:
Developing countries Developed countries
 travelers
 immigrants
 homosexual men
 HIV positive
 immunodeficiency states
poverty
Ignorance
overcrowding
Poor sanitation
malnutrition

4. Causative organism
3 species of entamoeba: E. dispar
: E. moshkovskii
: E. histolytica
Only E. histolytica is pathogenic. Other two
species are apparently non-pathogenic and
cause most of the asymptomatic cases.

5. Morphology
• Different form of E. histolytica:
1- trophozoite
2- precyst
3- cyst(1, 2, 4 nuclei)
• Quadrinucleated cyst is the infective stage
oval/round
resistant to chlorination
destroyed above 55 degree celsious and with disinfectants
• Trophozoite stage is feeding vegetative form which is
destructive to tissue

6. Trophozoites of Entamoeba histolytica with ingested
erythrocytes (trichrome stain)
The ingested erythrocytes appear as dark inclusions.
Erythrophagocytosis is the only morphologic characteristic that can be
used to differentiate E. histolytica from the nonpathogenic E.
dispar .
FE

7. Virulence factors
Trophozoites of E. histolytica interact with host
through a series of steps:
 Adhesion of target cell, cytopathic effect
 E.histolytica induces both Humoral and cell
mediated immune responses
 Causes disease only when invade the
Intestine
 Virulence is associated with secretion of
Cysteine proteinase (histolysin) which assists
the organism in digesting the extracellular
matrix and invading tissues

8. Cysts of Entamoeba histolytica
/E. dispar
• GHI
IHG
Cysts of Entamoeba histolytica/E.
dispar ,permanent preparations stained
with trichrome.

9. Transmission
1) feco-oral(direct hand-to-mouth contact)
2) Veneral transmission among homosexual males
3) Food or drink contaminated with feces containing the
E. histolytica cyst
4) Use of human feces (night soil) for soil fertilizer
5) contamination of foodstuffs by flies, and possibly
cockroaches
 a single cyst is sufficient to cause the disease
 Asymptomatic human( the only host) cyst
carriers are the principle reservoir of infection.

10. Pathogenesis
Ingestion of
cysts
Excystation in
small intestine
Production of 8
trophozoites
Multiplication
and Colonization
in large intestine
Tissue
invasion and
destruction
Flask – shaped
ulcers(mostly in
caecum, transverse
and sigmoid colon
Encystation
and exit from
host in the
stool
Migrate via
Blood stream(
portal
circulation) to
the liver Amoebic liver
abscess

13. Clinical features
Intestinal
• Asymptomatic
carriers(90%)
• Amoebic colitis
• Fulminant colitis
• Amoeboma
Extraintestinal
• Liver
• Lung
• brain
• skin
Incubation period : varies from weeks to months
: average= 3-4 weeks

14. Asymptomatic carriers
-90% without symptoms(non-invasive)
- lumen not damaged(cyst passers)
Invasive forms:
Amoebic colitis/dysentery
- flask shaped ulcers superficial or deep
- abd.pain, watery/mucoid blood-streaked foul-smelling diarrhoea
- fever, tenesmus, peri-anal ulcers
- sometimes intermittent diarrhoea
alternating constipation
Fulminant colitis - <0.5%
- severely ill with high fever
- profuse bloody diarrhea
- perforation(diffuse tenderness)
- paralytic ileus
-pronounced leukocytosis

15. • ulcers with raised borders
• little inflammation between lesions

17. Amoeboma
- 1% of cases
- inflammatory thickening of intestinal wall
- palpable mass with trophozoites
Symptoms of amoebic colitis
Symptoms Percentage
Diarrhea 100
Dysentery 99
Abdominal pain 85
Fever 68
Dehydration 5
Complications: toxic megacolon, amoeboma,
cutaneous amoebiasis, rectovaginal fistula

18. Amoebic v^s Bacillary Dysentery
symptoms Amoebic dysentery Bacillary dysentery
Occurrence Usu. In the form of sporadic cases Usu. In the form of outbreaks
Onset gradual Acute
Fever Usu. Low grade (may be high in case
of liver abscess)
High grade
Tenesmus/Abd. Cramps Moderate Very severe
Stool Foul- smelling Not foul-smelling
RBCs In clumps Discrete
Pus cells Scanty Numerous
Eosinophils Present Absent or rare
Bacteria Numerous, motile Scanty, non-motile
E. histolytica Trophozoites + Absent
Growth on culture Negative Positive

19. Extra-intestinal
Amoebic liver abcess(most common)
- 5% of invasive disease
- 10 times more common in men
-Usually no bowel symptoms except sometimes
-right upper quadrant tenderness
- hepatomegaly
- jaundice(10- 15%)
Pleuropulmonary/pericardial
- direct spread(transdiaphragmatic rupture)
from liver abscess (10%)
- hematogenous spread
-cough with crepitation
Similarly infection can spread to
brain, skin and genitourinary system

20. Investigation
Parasite detection
Antibody detection
Antigen detection PCR and other tests
Investigation

21. Parasite detection
1. Direct saline(wet) mount of feces:
- most common microscopic technique
-sample examined within 1 hour of collection
-3 stool samples taken on consecutive day ( since
sensitivity increased from 60% to 90%)
-presence of ingested erythrocytes within trophozoites is
pathognomic for E. histolytica
-carriers have only cysts in their stool
 Misidentification: macrophages v^s trophozoites
: PMN v^s cysts
: other entamoeba
2. Various culture techniques are available but
not done routinely

22. Antibody detection tests
• Routinely employed for extra-intestinal dz
– Positive(75%)- at presentation and 90%- beyond
1st week of symptoms
– ELISA is most sensitive
– IHA
– Latex agglutination
– Immunoelectrophoresis and immunodiffusion

23.  Antigen detection
• ELISA kits( sensitivity>90%): used in
epidemiological studies ; useful in endemic
areas
• Antigen detection by ELISA: is the ideal test –
distinguishes current from past infection.
 PCR
 OTHER TESTS: chest radiograph
: CT , MRI
: sigmoidoscopy
: peripheral blood- leukocytosis
without eosinophillia, mild anemia
: Alp, ESR are common lab findings.

24. • raised immobile right diaphragm
• Other imaging modalities show
– A single abscess in the right or left
lobe
– Multiple lesions can be present
Imaging
None of these
modalities can
differentiate amebic
abscess from pyogenic
or malignant one

25. Treatment of amebiasis
-combination of a luminal and a tissue
amoebicide is advocated for complete parasite
clearance in Invasive disease
Luminal amoebicides
• Diloxanide furoate
• diiodoquinol
• paromomycin
Tissue amoebicides
• 5-nitroimidazoles(DOC)
-metronidazole
-tinidazole
-secnidazole
• Chloroquin
• Dehydroemetine
Amoebic colitis: metronidazole followed by a luminal agent
Fulminant amoebic colitis: add an antibiotic to deal with bowel flora
Amoebic liver abscess: tissue amoebicide followed by luminal agent

26. treatment continued…………………
Asymptomatic intestinal carriers : a luminal agent
Treatment for only E. dispar is not nessary
Most patients show a response to a treatment( reduced
fever and abdominal pain) within 72-96 hrs.
Percutaneous therapeutic aspiration guided by
ultrasound or CT is reserved for:
-when lesion in the left lobe of liver
-when diagnosis is uncertain
- no response to metronidazole( persistent fever
and abd. pain) after 4 days of treatment
-large(>8-10 cm) ie. >300 ml of fluid
-severly ill patients

27. Amoebicide Pediatric dose Adult dose
Metronidazole 35-50 mg/kg/day for 7-10
days( in 3 divided doses)
750 mg 8 hourly
Tinidazole 50 mg/kg/day for 3 days(once
daily)
2 g once a day
Paromomycin 25-35mg/kg/day for 7 days(in
3 divided doses)
25-35mg/kg/day (in 3
divided doses)
Diloxanide furoate 20mg/kg/day for 7 days(in 3
divided doses)
500mg 8 hourly
Iodoquinone 30-40mg/kg/day for 20
days(in 3 divided doses)
650mg 8 hourly
DRUGS AND DOSES

28. PREVENTION & CONTROL
 Primary prevention
 Safe excreta disposal
 Safe water supply
 Hygiene
 Health education
 Treat symptomatic carriers
 Treat water(iodine, boiling): NOT
chlorine
 Secondary
 Early diagnosis
 Treatment