Entamoeba histolytica &

Giardia lambila

Entamoeba histolytica:

a protozoan parasite, cause amebiasis50000000 people worldwide suffer from E. histolytica infection

amebic dysentery and amebic liver abscess kill at least 40000-

110000 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)

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

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.

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 IIA 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 37C, P82/min, R 14min, BP 134/80 mmHgPE: 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

Inhabits in large intestine

Large intestine ulcers

Lung abscess

Live abscess Lung abscess

Brain abscess

trophozites

trophozites

cyst

trophozites

metastasis

Cysts orQuadrinucleate Cysts

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,

amoebapores form pores in host cell membranes

cysteine proteinases: cytopathic for host tissue

cell killing

phagocytosis

invasion

…

Ameba

1. Adherence

3. Cell killing

4. Phagocytosisand Invasion

2. Lect-in Signal

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 E. coli size 10-40 m 20-50 m

Trophozoite pseudopodium more transparent less transparent

movement active sluggish

inclusion RBC no RBC

karyosome centrol, small asymmetrical

size 12-20 m 15-25m

Cyst No. of nuclei 1-4 1-8

chromatoid rounded ends 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 thecommensals E. dispar is not possible by morphology but requires the use of species-specific 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.histolyticainfection, unless confirmed by visualization of ingested RBCsin the trophozoite, should be substantiated by (1) presence of RBCs in stool (2) serum antibody titer (3) stool E.histolytica antigen titer

Infection Drug and Dosage

Asymptomatic intestinal paromomycin 25-30mg/kg/D in 3 amoebiasis divided does for 7 days metronidazole 750 mg 3 time daily for 10 daysAmebic 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

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.

Naegleria

Acanthamoeba species cause granulomatous amebic encephalitis (GAE), amebic keratitis, corneal ulceration, amebic dermatitis

Balamuthia infection have cutaneous lesions and GAE

Acanthamoeba, Balamuthia

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 cyst- contaminated 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)