Transcript E. histolytica Cyst

Protozoa
(原虫)
General Account
• One-cell animal – monocellular or
unicellular organisms with full vital
functions
• Species – total named species:65,000;
parasitic: around 10,000
Classification of protozoa
Amoebae
Flagellates
Sporozoa
Ciliates
Life cycle patterns
One-host form
1. One stage form – Trophozoite
2. Two stage form – Trophozoite & Cyst
Two-host form
1. Mammals
2. Mammals
mammals
insect vectors
•
Mode of Reproduction
Asexual Reproduction



Binary fission – result in 2 daughter cells
Schizogony – multiple fission result in
multiple cells
Budding


•
Exogenous budding - by external budding result
in multi- cells
Endodyogony - by internal budding result in 2
cells
Sexual Reproduction


Conjugation – exchange of nuclear
material of 2
Gametogony – sexually differentiated cells
unite -- zygote
Pathogenesis
• Host Resistance
– Innate immunity
– Acquired immunity
• Parasite Invasion
– Toxin
– Mechanically damage
– Immune impair
• Immune inhibition
• hypersentivity
Opportunistic & Accidental
(protozoa) infections
Opportunistic parasites
• Opportunistic infection
– An infection by a microorganism
that normally does not cause
disease but becomes pathogenic
when the body's immune system is
impaired and unable to fight off
infection
Amoebic Infections
Entamoeba histolytica
Acanthamoeba
Naegleria
Epidemiology
• 4th leading cause of death from parasitic diseases
worldwide
Organism
# of deaths/yr
# infected
Entamoeba
~75,000
~300 million
Ascaris
Schistosoma
Plasmodium
(Malaria)
~200,000
~750,000
2-3 million
~480 million
~200 million
~500 million
• Amoebiasis is not restricted to the tropics and
subtropics, it also occurs in temperate and even in
arctic and antarctic zones
Contaminated water is a source of infection.
Infection is common in developing countries where sanitation is poor.
Amoeba in alimentary tract
• Entamoeba
–
–
–
–
–
E.
E.
E.
E.
E.
histolytica (pathogenic)
dispar (non-pathogenic)
coli (big sister)
hartmani (little brother)
gingivalis (oral)
• Endolimax nana (occasionally pathogenic)
• Iodamoeba butschlii
Morphology
Entamoeba histolytica
Cysts
Trophozoites
Thick wall
Plasmalemma (thin)
1-4 ring-like nuclei
1 ring-like nucleus
Chromatoid body (blunt)
Lacking
Round, 10-16 μm
Irregular, 10-60 μm
Concentratable
Labile
Morphology
Ingested
RBC
Endoplasma
Ectoplasma
Nucleus with central
karyosome and finely
divided chromatin
granules
Pseudopod
E. histolytica trophozoite
Morphology
Trophozoites
Single nucleus with a central,
dot-like karyosome
Micrograph of a trophozoite ingesting a red blood cell deprived from its host.
Morphology
1-4 ring-like nuclei
with finely divided
peripheral chromatin
Cyst wall and
round shape
Mature E. histolytica Cyst
Morphology
Morphology
E. Coli trophozoites
•
E. Coli cysts
•
Morphology
E. histolytica Stages - CYSTS
• Infective Stage for humans
• Resistant walls maintain viability
– If moist can last several weeks
– Killed by desiccation or boiling
• Diagnostic Stage in formed stools
– Can be concentrated and stained easily
– Not seen in liquid (diarrheic) stools or
tissues
E. histolytica Stages - TROPHOZOITES
• Cause amoebiasis (damage tissue)
• Spread throughout the body, but ...
– Rarely transmit the infection to others
• Labile in liquid stools or tissue, and
– must be rapidly found or preserved
(quick fixation & cold storage) for
Diagnosis
Life cycle
Life cycle
• Humans acquire E. histolytica by:
– Ingesting cysts (4 nuclei mature) in
fecally contaminated food or water
– Rarely by directly inoculating
trophozoites into colon or other sites
– (anal sex?)
• Fecal-Oral transmission (hand to
mouth)
Life cycle
• The basic generation-cycle: cyst –
lumen trophozoites – cyst
• Trophozoites may invade intestine
and spread
• Cyst formation – essential factors:
enviroment + time
• Infective cysts and trophozoites
pass in feces
Pathogenesis
General Types of Virulence Factors:
• Adherence factors
• 260kDa Gal/GalNAc lectin
• Invasion factors
• Amoeba pores
• Cysteine proteinases
• Endotoxins
Pathogenesis
Trophozoites ...
– Attach to mucosal epithelial cells
(MEC)
– Lyse MEC
– Ulcerate and invade mucosa
– Cause
dysentery (diarrhea + blood)
– Metastasize via blood &/or lymph to
– Form abscesses in extraintestinal
sites ...
Clinical Classification of
Amoebiasis
(World Health Organization)
• Asymptomatic Infection:"Cyst
Passers/carrier”
• Symptomatic Infection:
– Intestinal Amoebiasis:
(colon and rectum盲肠、
升结肠、直肠、乙状结肠和阑尾)
• Acute Dysenteric (dysentery)
• Chronic Non-Dysenteric (“self-cured”)
– Extra-Intestinal Amoebiasis:
• Amoebic Liver Abscess (ALA)
• Amoebic Pulmonary Abscess
• Other sites (brain, skin, GU, ?)
Clinical classification
• Asymptomatic infection
(carrier) >90% (E. dispar?)
• Symptomatic cases <10%
– 8% -10% dysentery, colitis, etc
– 2% invasive amoebiasis
– 0.1% deaths
Clinical manifestation
Acute Dysenteric Amoebiasis
Symptoms:
Bloody mucoid diarrhea
RBCs and few WBCs in stools
– Abdominal pain
– weight loss
– bloating, tenesmus(里急后重)
and cramps
Clinical manifestation
Acute Dysenteric Amoebiasis
Signs:
Fever (33%)
Tender (enlarged) liver
Stools positive for trophozoites +/- WBC
NO cyst in loose stools
Clinical manifestation
•


Pinpoint lesion on
mucous membrane
Flask-shaped crateriform
ulcers
Pathological changes in large intestine
Clinical manifestation
Chronic Non-Dysenteric Amoebiasis
“self-cured” carrier state
Usually for 1 year, 37%
symptomatic >5 years
Intermittent diarrhea, mucus,
abdominal pain, flatulence and/or
weight loss
E. histolytica trophs in loose stools
Cysts in solid stools
Positive serology and ulcerations on
sigmoidoscopy or pathologic test
Clinical manifestation
Extra-Intestinal Amoebiasis
Amoebic Liver Abscess (ALA)
• Symptoms
– History of dysentery (1 yr), weight
loss, abdominal pain, chest or
shoulder pain
• Signs
– fever, hepatomegaly
– Diagnostic aspiration:non-odorous, reddish-brown in
color aspirate (chocolate jam) "anchovy paste"
– Might find trophozoites in the aspirate
– Skin inflammation
Clinical manifestation
Ulcers caused by invasion of E. histolytica into the liver.
Clinical manifestation
•
Clinical manifestation
An Amoebic Liver Abscess Being
Aspirated.
• Note the reddish brown
color of the pus
(‘anchovy-sauce’). This
color is due to the
breakdown of liver cells.
Gross pathology of amoebic abscess of liver.
Tube of "chocolate" pus from abscess.
Clinical manifestation
X-ray of Amoebic Liver Abscess
•
Diagnosis
• Pathogenic diagnosis
– Stool examination:
• Direct Fecal Smear (trophs and cysts)
• Fecal concentration and iodine dye techniques (cysts) ZnSO4 or formalin-ether
– Cultivation
– DNA detection
– Sigmoidoscopy
• Serologic Tests (for chronic disease):
ELISA, IHA (indirect hemagglutination)
• Imaging: X-ray; CT
Stool examination
specimen
method
diseases
remarks
trophozoite
cyst
loose feces
solid feces
direct smear with normal
saline
direct smear with iodine
stain
amoebic dysentery
chronic intestinal
amoebiasis or carriers
1.container must clean
2.examined soon after they have
been passed.
3.select bloody and mucous
portion.
Two microscopically
indistinguishable Entamoeba sp.
• E. histolytica
– invades tissues
– should always be treated
• E. dispar
– is non-pathogenic, even in AIDS
– should not be treated
Treatment of Amoebiasis
• For invasive forms:
metronidazole
• For luminal forms:
Iodoquinofonum, paromomycin,
diloxanide
• Do not treat asymptomatic
intestinal E. dispar infection
Treatment of Amoebiasis
Location
Clinical Class
Drug Name
Drug Action
Asymptomatic
Iodoquinofonnum(喹碘方)
lumenal amebicide
Mild to moderate
intestinal disease
Metronidazole（甲硝唑）
tissue amebicide
Severe intestinal
disease
Metronidazole plus a lumenal
drug
both
Hepatic disease
Metronidazole plus a lumenal
drug
both
Intestinal
Extraintestinal
Prevention & Control
• Individual measures
• Diagnosis and treatment of E. histolytica patients
• Safe drinking water (boiling or 0.22 µm filtration)
• Cleaning of uncooked fruits and vegetables
• Prevention of contamination of foods
• Chemotherapeutic Trial
Prevention & Control
Community measures
– Public services and utilities
• Adequate disposal of human stools
• Safe and adequate water supply
– Primary health care systems
• Health education (washing hands, cleaning and protecting
food, controlling insects)
• Specific surveillance programs and Control programs
integrated into ongoing sanitation & diarrhea control
– Health Regulations
• Control of food vendors and food handlers
• Control of flies and cockroaches
Infections with
Free Living Amoebae
Naegleria 耐格里属
Acanthamoeba 棘阿米巴属
Free Living Amoebae
Not seen
in humans
Naegleria
i
10-35 µm (smaller than A. spp.) i
with lobate pseudopodia
i
15-45 µm with filiform pseudopodia
Acanthamoeba
cysts & trophs
are seen in
humans
Acanthamoeba spp.
Acanthamoeba
trophozoites with
acanthopodia
Primary Amoebic Meningoencephalitis
PAME
An acute suppurative infection of the
brain and meninges that is rapidly fatal
and usually not diagnosed antemortem
– Caused by Naegleria fowleri
– Headache, lethargy and olfactory problems
– Sore throat, runny nose, severe headache,
vomiting, stiff neck, confusion leading to ...
– Coma and death
DIAGNOSIS
PAME
• Patient History (child)
– Prior Health Excellent
– Recent History of Swimming (fresh
water/pools)
– Cases peak during HOT months
• Symptoms/Signs
– Sore throat, runny nose, headache,
vomiting, stiff neck, mental confusion,
olfactory problems, lethargy, coma and
death
Treatment
– None effective - few patients survive
– Amphoteracin B +/- ?
PAME
Granulomatous Amoebic Encephalitis
GAE
A more slowly progressive, chronic form of
the disease not associated with swimming
(except in hot tubs)
• cause: Acanthamoeba castellanii
• history of subcutaneous nodules, eye or
skin infection, progressive nasal congestion,
headache ...
• CNS lesions with negative serology for
toxoplasmosis
• in debilitated/immuno-compromised Pts
with CD4+ TL <200/mm3
• disseminated infection: skin, sinuses, lungs,
CNS/CSF
Pathology
GAE
• abscesses/lesions (tissues) have
– granulomatous inflammation
– hemorrhagic necrosis and vasculitis
– trophozoites & cysts with wrinkled-walls!
• amoebae rarely seen in CSF
Treatment
GAE
• No satisfactory or effective treatment ?
– amphotericin B
Acanthamoeba Keratitis
AK
Corneal infection with
Acanthamoeba spp. trophozoites
& cysts
• Ulcerations & “Ring Infiltrate” of
cornea
• Induced by
– trauma to eye, exposure to
contaminated H2O
– contact lens wear with tap water
rinsing
AK
• Diagnosis
– Examine corneal scrapings or smear
– Histopathologic examination of
cornea
• Treatment
– Triple Antiamoebic Therapy
• neomycin-polymyxingramicidin/propamidine/miconazole
– Penetrating keratoplasty (cadaver
cornea)
Summary
• E. histolytica
– Life cycle, pathogenesis, Diagnosis,
treatment
– carrier
– Morphology differences with E. coli
• Free living amoeba
– prevention
QUESTIONS
• How to diagnose hepatic amoebiasis?
• What are the transmission route of E.
histolytica ?
• Who should be treated for amoebic
infection?
• How will one get amoebiasis? What
are the consequences?