Download E. histolytica

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)
Plasmodium (疟原虫)
History
 Malaria is an old infectious disease. The first
documentation about it is at 1500BC.
 Until the end of the 19th century, it was
commonly thought that malaria was caused
by breathing bad air (mal-aria) and was
associated with swamps
History
Important application of the
knowledge
about
malaria:
W.
Gorgas successfully implemented
control strategies for malaria and
yellow fever during the construction
of Panama Canal
Global distribution
Plasmodium that infect
human
Malaria current status
Morphology
•
Plasmodium is the one-cell parasite, so the
basic morphology is a nucleus (chromatin),
cytoplasma and cell membrane
•
Wright or Giemsa stain gives the
Cytoplasm – bluish; Chromatin - red to
red-purple while the malarial pigments are
yellow-brown
•
There are three stages and six main
forms of plasmodium in RBC
Plasmodium in RBC
Trophozoites (滋养体期)：ring form and
developing trophozoites
Schizonts (裂殖体期)：immature and mature
-- merozoites
Gametocyte (配子体期)： Microgametocytes
and macrogametocytes
Trophozoites
• Fig. 1: normal red cell; Figs. 2-5: ring stage
parasites (young trophozoites)
Ring form trophozoites
Thin blood film (Giemsa
stained)
• Ring like plasma with one nucleus at
one side
Mature trophozoites (amoeboid form)
• The plasmodium grow with pseudopods,
more cytoplasma and malarial pigment
presented in the plasma
• Red blood cell enlarged and became pale
with Schüffner‘s dots(薛氏小点)
Schizonts
• Figs.： increasingly mature
schizonts
Macrogametocyte (female gametocyte)
of P.v
• Giemsa staining
• compact nucleus, usually at edge of the
parasite
• scattered pigment granules
• The gametocyte is completely filling its host
cell
Microgametocyte (male gametocyte)
of P.v
• Giemsa staining
• large nucleus at the center of the cell
• scattered pigment granules
Macrogametocyte of P. f
• The crescent-shaped
gametocytes of P. falciparum
are very distinctive, but tend to
only appear late in the infection
• Compact nucleus, red, usually
at the center of the cell
• Malarial pigments around the
nucleus
Microgametocyte of P. f
• Sausage-shaped
with two blunt end
• Large nucleus at the
center
• Sometimes hard to
distinguish from the
female gametocytes
exo-erythrocytic stage—
merozoites in liver cells
The vector – female
Anopheles
Development in the
vector
Gametocytes
sporozoites
zygote
oocyst
Life Cycle
Life cycle
• Infective stage：sporozoites
• Transmission
–
–
–
–
female Anopheles mosquito
transfusion
transplacental
needle stick
• Pathogenic stages：erythrocytic
stage
• Diagnositic stages：erythrocytic
stage
Pathogenesis
Clinical features
Incubation period （潜伏期）
• Time interval between the mosquito bite and
the onset of the clinical symptoms
• Time for the sporozoite reaching liver and entering
• Duration of the development in the liver
• Time of development in the RBC to produce
sufficient erythrocytic merozoites to cause clinical
symptoms
– P. falciparum 7 to 27 days
– P. vivax 8 to 31 days
– P. malarie 18 to 40 days
– P. ovale 16 to 18 days
Clinical features
Typical malaria paroxysm（发作）

Malarial paroxysm -symptom for
erythrocytic phase
– RBCs rupture releasing merozoites, malarial
metabolites, endotoxin in blood
– shaking chill（寒战） followed by fever （高热）
(2-20 hrs)
– profuse sweating when fever breaks（出汗退热）
– repeated characteristic cycle for each species
P. falciparum 36-48hrs
P. vivax 48hrs
P. malariae 72hrs
P. ovale 48hrs
Recrudescence versus
relapse
• Recrudescence （再燃） is the return of the
symptom of malaria after apparent cure,
which is due to a sudden increase in what
was a persistent, low-level parasite
population in the blood.
– The periodic increase in numbers of parasites
results from a residual population persisting at
very low levels in the blood after inadequate or
incomplete treatment of the initial infection.
– The asymptomatic situation may last for as long
as 53 years.
Recrudescence versus
relapse
• Victims may suffer relapse （复发）after
apparent recovery of malaria. This is caused
by the long prepatent sporozoites (LPPs) or
hypnozoites which remain dormant in the
hepatocytes for an indefinite period.
– P. vivax and P. ovale will develop hypnozoites in the
liver responsible for relapse while patients infected
with P. falciparum and P. malariae have no
phenomenon of relapse
• All four types of plasmodium can maintain low
level of parasitemia and account for the
recrudescence of the disease
Clinical features
• liver & spleen damage of long-term
• complications from P. falciparum
–Anemia
– tropical splenomegaly syndrome
–cerebral malaria - 50% of deaths
•coma and renal failure due to
tubular necrosis
tropical splenomegaly syndrome
Cerebral malaria
Diagnosis
• Travel history to endemic area & presence
of symptoms, e.g., fever and chills
• Thick smears - hard to read
• Thin smears - see RBC morphology and
parasite characteristics
• serology - helps rule out fever of unknown
origin
• DNA probes- too slow & costly esp. in field
Diagnosis
Thick blood smear
Thin blood smear
Indirect fluorescent antibody
test （IFA）
DNA--PCR
• Lane S: molecular base
pair standard (50-bp
ladder). Black arrows show
the size of standard bands.
• Lane 1: P. vivax (size: 120
bp)
• Lane 2: the red arrow
shows the P. malariae (size:
144 bp)
• Lane 3: P. falciparum (size:
205 bp)
• Lane 4: P. ovale (size: 800
bp)
Treatment
• Quinidine, chloroquine, primaquine,
pyrimethanime, sulfadoxine,
mefloquine, tetracycline, proguanil
• affect parasite in different ways
depending on stage when
administered
• different species react differently
• emergence of drug-resistant malaria
Prevention and control
• Personal protection- netting,
repellents, etc.
• mosquito control or eradication - not
easy
• avoid sharing needles
• develop vaccines - not currently
available
• select proper treatment for species
and morphological forms