1. AMEBIASIS AND INFECTION WITH
FREE LIVING AMEBAS
Dr R L Khare
Assistant Professor
Department of Medicine
Pt JNM Medical College Raipur

2. DEFINITION

Amebiasis is infection with intestinal pathogen
Entameba histolytica (tissue lysing ameba)

Most Infection are asymptomatic

Can cause disease ranging from Dysentry to
extaintestinal infectons like liver absess

Most of asymptomatic infection is due to E.dispar

Endemic area Mexico,India & tropical regions of
Africa,South and Central America

3. LIFE CYCLE AND TRANSMISSION

E. histolytica exists in two stages
multinucleate cyst
Motile Trophozoite

4. TRANSMISSION
E. histolytica are most common in areas where
poor sanitation and crowding compromise the
barrier to contamination of food and drinking water
 Infection is acquired by ingestion of cysts in faecally
contaminated water or food or rarely,through oralanal sexual contact
 Cysts are resistant to the acid in the stomach


5. LIFE CYCLE

6. PATHOGENESIS AND PATHOLOGY

E. histolytica posses a potent repertoire of

adhesins, proeinases and pore forming proteins and
other molecules that enable them to lyse cells and
tissue
These mol. Induce cellular necrosis and apoptosis
 Resist both innate and adaptive immunity
 E. histolytica trophozoites adhere to the colonic
mucosal epithelial cells leads to disruption
 Adherence is mediated by a family of surface lectin
molecules capable of binding to galactose and Nacetylgalactosamine residues


7. PATHOGENESIS AND PATHOLOGY
E.histolytica can lyse host cells upon contact
through a family of amphipathic peptides called
amoebopores
 E.histolytica
posses a large family of cysteine
proteinases that are capable of lysing the
extracellular matrix between the cells and cleaving
host defense molecules (complement and
antibodies)
 The ultimate effect of all these amebic virulance
factors on the human colon is the production of
small ulcers that have heaped borders and contains
focal areas of epithelial cell loss


8. PATHOGENESIS AND PATHOLOGY

The interveining mucosa is normal

E.histolytica trophozoites can then invade laterally
through the submucosal layer, creating the classic
flask shaped ulcers that appear
on pathologic
examination as narrow-necked lesions broadin the
submucosal region

E.histolytica trophozoites found at the margin
between dead and the live tissues

9. FLASK SHAPED ULCER

10. CLINICAL MANIFESTATIONS
Two types- Intestinal and Extra Intestinal
 Most patients harboring Entamoeba species are
asymptomatic,but individuals with E.histolytica can
develop disease
 Amebic colitis generally appear 2-6 weeks after
ingestion of the cyst of parasite
 Heme positive diarrhea and abdominal pain are the
most common complaints
 Malaise and wt.loss may be found later
 Fever is present in 40% cases
 Severe dysentry with 10-12 small volume, blood
and mucus containing stools may develop


11. CLINICAL MANIFESTATIONS
Fulminant amebic colitis with even profuse
diarrhea,severe
abdominal
pain,fever,and
pronounced leukocytosis are rare
 It
affects young children,pragnant women,
indivisuals treated with steroids and pts. With
diabetes and alcoholism
 Intestinal perforation occus in >75% of pts.with
fulminant disease
 Complications includes

Toxic Megacolon in .5% with severe bowel dilatation and
intraluminal air
 Ameboma-presents as abd. mass


12. AMEBIC LIVER ABSCESS
Most cmmon extraintestinal complication
 Disease begins when trophozoites penetrate
through the colonic mucosa, travel through the
portal circulation and reach the liver
 The classical presentation of ALA are right upper –
quadrant pain,fever and liver tenderness
 Its acute in nature lasting < 10 days
 With chronic presentation wt. loss and anorexia are
prominent
 Jaundice is uncommon


13. OTHER MANIFESTATIONS AND COMPLICATIONS
Rt-sided pleural effusion and atelectesis are
common in cases of ALA
 In 10% rupture of abscess through diaphragm may
cause pleuro-pulmonary amebiasis
 Sudden onset cough,pleuritic chest pain and
shortness of breath are suggestive symptom
 Hepatobronchial fistula is dramatic complication in
which pt has complaint of cough with content of liver
abscess
 Liver abscess may rupture into pericardial cavity
and can cause pericarditis with 30% mortality due to
cardiac temponade


14. DIAGNOSTIC TESTS
Demonstration of E.histolytica or cyst in the stool
or colonic mucosa of pts with diarrhea
 Antigen
detection based ELISAs that can
specifically identify E.histolytica in the stool
probably represent the best choice in the endemic
areast
 PCR assay for DNA in the stool samples is
currently the most sensitive and specific method for
identification but used as research and
epidemiological tool


15. DIAGNOSTIC TESTS
Diagnosis of amebic liver abscess is based on the
detection of one or more space occupying lesions
in the liver by Ultrasound and CT scan and a
positive serology
 Amebic liver abscess are classically described as
single, large and located in right lobe of liver
 When a pt. with space ahs a occupying lesion in the
liver, a positive serology is highly sensitive(>94% )
and highly specific(>95%) for the diagnosis of the
liver abscess


16. CT SCAN LIVER WITH ALA IN RT LOBE

17. TREATMENT
The nitroimidazole compounds are the drug of
choice
 To
date E.histolytica has not demonstrated
resistance to any of the compound metronidazole
and tinidazole
 Tinidazole appears to be better tolerated
 Whenever possible fulminant amebic colitis should
be managed conservatively


18. TREATMENT

Aspiration of liver abscess reserved for





the indivisual in whom pyogenic abscess
a bacterial superinfection is suspected but diagnosis is
uncertain,
for pts failing to respond to tinidazole or metronidazole (
those who have fever or abdominal pain after 4 days of
treatment),
for indivisuals with large liver abscesses in the left lobe
large abscsee with risk of rupture

19. TREATMENT
In contrast, aspiration and percutaneous catheter
drainage improves outcome in pleuropulmonary
amebiasis and empyema
 Percutneous drainage or surgical drainage is
absolutely indicated in amebic pericarditis
 Rupture of an amebic liver abscess in peritoneum is
managed conservatively with medical therapy and
percutaneous catheter drainage


20. TREATMENT
Neither metronidazole nor tinidazole reaches high
levels in the gut lumen therefore, patients with
amebic colitis or ALA should also receive treatment
with luminal agents (Paramomycin or iodoquinol) to
ensure eradication of infection
 Paramomycin is preferred agent
 Nitazoxanide, abroad spectrum antiparasitic drug,is
efficacious against E.histolytica trophozoitesin the
both tissue and gut


21. TREATMENT
Drug
Dosage
Duration
Tinidazole
2g/day with food
3
Metronidazole
750mgtid PO or IV
5-10
Paramomycin
30mg/kg qd PO in 3
divided dose
5-10
Iodoquinol
650 mg PO tid
20
Amebic Colitis Or ALA
Luminal Infection

22. PREVENTION
Avoidance of ingestion of food and water
contaminated with humen feces is the only way of
prevention
 No prophylaxis
 No vaccine
