Entamoeba histolytica
&
Giardia lambila
Entamoeba histolytica:
a protozoan parasite, cause
amebiasis
50000000 people worldwide suffer from E. histolytica infection
amebic dysentery and amebic liver abscess kill at least 40000110000 individuals yearly
the second leading cause of death among parasitic diseases
Giardia lambila:
a major cause of diarrheal outbreaks from contaminated
water supplies
resides small intestine ( duodenum), gallbladder, causing
giardiasis or ‘‘traveler’s diarrhea’’
common in children with younger age, with a high incidence
among tourists & homosexual male,
opportunistic protozoa (parasite)
Case study I
A 36 year old man presented to the emergency department of
a general hospital with 10 day history of intermittent diarrhea
and tenesmus, with blood and mucus visible in the stool.
He had just returned from a working trip to India, where he
had visited a rural town in the last week of his trip.
Physical Examination:
VS: T 38.8 C, P96/min, R 16/min, BP 130/80 mmHg
PE:
Ill- appearing male in mild distress; abdominal
exam revealed mild diffuse tenderness, and rectal
exam was positive for blood
Laboratory studies
WBC: 11600/l
Differential: 72% PMNs 20% lymph
Imaging
Sigmoidoscopic examination revealed multiple small
hemorrhagic areas with ulcers
Microscopic exam as following
Case study II
A 25 year old man presented to a hospital clinic with a 2 week
history of sustained diarrhea (three to five bowel movement per day),
nausea, flatulence, and lack of appetite. He described his diarrhea
as initially watery, and then greasy and foul smelling. He added that
he had a bloating sensation. He did not have fever or chills.
The patient had been in good health. Four weeks previous to seeing
his physician, he had visited a rural town for several days.
Physical Examination:
VS: T 37C, P82/min, R 14min, BP 134/80 mmHg
PE: abdomen was distened and mildly tender,
no hepatosplenomegaly. Rectal exam was normal.
Laboratory studies:
WBC: 6300/l Differential: normal
Serum chemistries: BUN 22 mg/dl creatinine 1.2 mg/dl
Microscopic exam and duodenal aspirate exam as following
Brain abscess
Lung abscess
Live abscess
Large intestine
ulcers
Lung abscess
Inhabits in
large intestine
metastasis
trophozites
Cysts or
Quadrinucleate
Cysts
trophozites
cyst
trophozites
Pathogenesis & Symptoms
Pathogenesis
ingestion of the quadrinucleate cyst of E. histolytica from
fecally contaminated food or water initiates infection
infection also occurs through direct person-to- person
contact
inhabits the large intestine, invade the mucosal crypts,
feed RBCs & form ulcers
Pathogenic factors:
Lectin adherence to host cells, in signal,
cell killing
amoebapores form pores in host cell membranes
phagocytosis
cysteine proteinases: cytopathic for host tissue
…
invasion
1. Adherence
Ameba
4. Phagocytosis
and Invasion
2.
Lectin
Signal
3. Cell killing
amoebic invasion through the mucosa and into the
submucosal tissues is the hallmark of amoebic colitis
the lateral extension through the submucosal tissues
gives rise to the classic flask-shaped ulcer of amoebiasis
or ameboma
amebic liver abscess is the most common manifestation
of extrainintestinal disease
the most serious complication of amoebic liver abscess
are rupture
Symptoms
asymptomatic/Carrier state: the amoebae may reproduce
but the patient shows no clinical symptoms
symptomatic intestinal amebiasis: may complain of more
specific symptoms, including diarrhea, abdominal pain
and chronic weight loss
symptomatic extraintestinal amebiasis: the formation of
an abscess in the right lobe of the liver , trophozoites
extension through the diaphragm, causing amebic pneumonitis
(abscess) brain abscess
Diagnosis
Microscopic examination
a direct saline wet mount------trophozoites, cyst
from pus------ trophozoites only
iodine stain------------------------cyst
concentration techniques
permanent stained
E.histolytica
size
Trophozoite pseudopodium
movement
inclusion
karyosome
Cyst
size
No. of nuclei
chromatoid
E. coli
10-40 m
more transparent
active
RBC
centrol, small
20-50 m
less transparent
sluggish
no RBC
asymmetrical
12-20 m
1-4
rounded ends
15-25m
1-8
splintered ends
Immunologic techniques
monoclonal antibody detected
antigen from stool or pus
detected specific antibodies by antigen
ELISA, IFA, IHA
PCR techniques
16S rRNA, Prx gene …
differentiation of E.histolytica from the
commensals E. dispar is not possible by
morphology but requires the use of speciesspecific Mab or PCR techniques
Imaging
colonoscopy, Sigmoidoscopic examination -----biopsy
sonography, computed tomography (CT),
magnetic resonance imaging (MRI)
Epidemiology
generally higher in the tropics, subtropics, and poor sanitation,
poor nutrition
(for example)
a high-carbohydrate diet, alcoholism, genetic makeup, bacteria
infection of the intestine, local injury to the colonic mucosa
the true prevalence of E. histolytica is perhaps closer to 1%
to 5% worldwide
the realisation that E. histolytica & E.dispar are morphologically
identical species with remarkable different physiological and
pathogical characteristics has impacted on all aspects but notably
on the epidemiology
no sexual preference for intestinal amoebiasis, but amebic liver
abscess is 3 to 10 times more common in men
the high-risk group for amebiasis include travelers,
institutionalized mental patients, promiscuous homonsexual
a severe form of infection in neonates, pregnant women, women
in the postpartum period, immunocompromised patients, patients
with malnutrition or malignancy
ingestion of the infective cyst, through hand – mouth
contamination & food /water contamination
flies & cockroaches may also serve as vectors of E. histolytica
Treatment & Prevention
Whenever possible, a laboratory diagnosis of E.histolytica
infection, unless confirmed by visualization of ingested RBCs
in the trophozoite, should be substantiated by (1) presence of
RBCs in stool (2) serum antibody titer (3) stool E.histolytica
antigen titer
Infection
Asymptomatic intestinal
amoebiasis
Drug and Dosage
paromomycin 25-30mg/kg/D in 3
divided does for 7 days
metronidazole 750 mg 3 time daily
for 10 days
Amebic dysentery and liver abscess metronidazole 750 mg 3 time daily
Ameboma
for 10 days follow by paromomycin
Metronidazole and tinidazole are first-line agents in the
treatment of acute amebic colitis and amebic liver abscess
therapeutic aspiration of an amebic liver abscess is occasionally
required as an adjunct to antiparasitic therapy
the prevention of amebic infection starts with avoidance of
fecally contaminated food and water.
The high incidence of amebiasis in recent community-based
studies suggests that an effective vaccine would improve
public health.
Free-living amoebae
--- Naegleria, Acanthamoeba, Balamuthia
Naegleria
Human beings usually acquire Naegleria infection from swimming
in the contaminated water or contaminated pipeline
Naegleria fowleri caused primary amebic meningoencephalitis
(PAM), an acute, suppurative infection of the brain and meninges.
Acanthamoeba, Balamuthia
Acanthamoeba species cause granulomatous amebic encephalitis
(GAE), amebic keratitis, corneal ulceration, amebic dermatitis
Balamuthia infection have cutaneous lesions and GAE
a wet mount of cerebrospinal fluid (CSF) is usually
more useful
detection of motile organisms is a diagnostic finding, but they
must distinguished from motile leukocytes
to detected of parasites a culture is in order
DNA-based or Mab-based technique may also help for
difference diagnosis
the drug of choice for the treatment of PAM is amphotericin B
the treatment of GAE has not been standardized
the treatment of AK includes systemic antifungal drugs,
tropical antiamebic eye drops, and surgical debridement
of the ocular lesions
Giardia lamblia
Trophozoites of Giardia are fund in the upper part of the
small intestine ( duodenum), gallbladder, causing
giardiasis or ‘tourist diarrhea
Giardia is worldwide in distribution
Giardia lamblia is considered to be one of the major cause of
parasitic diarrhea
Human infection mainly results from ingestion mature cystcontaminated food or water
excystation occurs in the upper regions of the small intestine,
where the trophozoite resides & multiplies by binary fission
trophozoites pass through the digestive tract, encyst in the
colon & transformed into cysts, pass in the feces
cysts with highly resistant
Infections with G. lamblia are often completely asymptomatic
Extensive ulceration of mucosa may occur in heavy infection
symptomatic infection may cause intestinal disorders, most
commonly diarrhea------Vit A & soluble fat, nausea,
flatulence, weight loss
a direct saline wet mount------trophozoites, cyst
iodine stain------------------------cyst
concentration techniques
duodenal aspiration
entero test -----an alternative & more satisfactory
technique for trophozoites detection
Imaging
DNA-based or Mab-based technique may also help for
difference diagnosis
common in children 6-10 years of age,
with a high incidence among tourists &
homosexual male,
opportunistic protozoa (parasite)
Metronidazole is most common drug
in treatment (Tinidazole Paromomycin)