Transcript 07-Toxoplasma LEC Stud

‫بسم هللا الرحمن الرحيم‬
Cryptosporidium parvum
Cryptosporidiosis
zoonosis, cosmopolitan, most human and
animals infected by Cryptosporidium
parvum
Life cycle
• Infective stage :oocyst with
4sporozoites passed in feces.
• Upon ingestion sporozoites are released.
• Sporozoite penetrate intestinal epithelial
cells and undergo two cycle :
1-schizogony
2-gametogony.
• Sporulated oocyst ,4-5M (with 4
sporozoites) are passed in feces.
duodenal biopsy sample from a patient
with AIDS and cryptosporidiosis
Pathology & clinical picture:
• Immunocopetent persons asymptomatic
or mild enterocolitis ,last about 2
weeks.
• Immunodeficient persons sever
diarrhoea with malabsorption.
Diagnosis & morphology:
• duodenal biopsy :gametes or schizont
(4-8 merozoites) in epithelial cells.
• Stools :oocyst 4-5 m with 4
sporozoites (without sporocyst).
• Treatment
- Self limited in immunocomptant
persons ,no effective drugs in cases
of AIDS.
- Management of fluid and electrolytes
loss.
• Prevention and control:
-person-to person or animal to person
transmission controlled by sanitation.
-Identify common sources e.g.
contaminated water
Toxoplasma Sporozoite
4-5M
Toxoplasma gondii
•T. gondii is an obligate
intracellular parasite
•life cycle includes both
sexual and asexual
proliferation and
transmission.
• The sexual cycle takes
place in the intestinal cells
of the cat family.
The cat are final hosts for the
sexual stages of T. gondii.
• After ingestion of tissue cysts,
parasites invade the enterocytes,
undergo several division (asexually)
and differentiate into
gametocytes.
• The gametocytes form a zygote
or ‘oocyst’ that is shed into the
environment with the cat’s faeces.
• The oocyst takes 1 to 5 days
after excretion to sporulate
• The oocyst with (8) of highly
infectious ‘sporozoites’ may
persist for years in a moist
environment.
• Sporulated oocyst resist
disinfectants, freezing, and
drying, killed by heating (70°C
for 10 minutes).
• After ingestion by a mouse the
sporozoites differentiate to the
rapidly dividing ‘tachyzoite’
Sporulated oocyst
oocyst
unsporulated
Human infection
• A) ingestion of undercooked
infected meat containing cysts .
• B) ingestion of the oocyst from
contaminated hands or
food (CAT`s feces)
• C) organ transplantation or blood
transfusion;
• D) transplacental (congenital)
• E) accidental inoculation of
tachyzoites.
Toxoplasma cysts are
found in skeletal muscle,
myocardium, and brain;
these cysts may remain
throughout the life of
the host
CYCLE IN INTERMEDIAT HOST
(MAN)
• Sporozoites released from
the oocyst penetrate the
intestinal mucosa and find
their way into macrophages
divide very rapidly (named
tachyzoites) and form
a cyst occupying the whole
blood macrophage (Pseudocyst
containing tachyzoites)
•The infected cells burst and
release the tachyzoites to enter
another cells, including muscle
and nerve cells, and multiply
slowly (bradyzoites).
• These cysts are infectious to
carnivores (including man).
•man is a dead-end host.
Toxoplasma cyst in brain
tissue (Bradyzoites)
Pathogenesis
•Host cells are destroyed by
active multiplication of
parasites producing necrotic
foci.
•Congenital infection often
involves the retina and brain;
focal chorioretinitis result in
impaired vision.
•Brain involvement in
immuno-suppressed patients
may lead to large necrotic
abscesses.
•Disease reactivation in
immuno-suppressed patients
may result from the
rupture of a tissue cyst.
• During the acute infection,
congenital transmission to fetus
can occur.
• Latent bradyzoite (tissue cysts)
persist for the life of the
host,can re-emerging,but do not
produce overt disease in healthy
individuals.
• Carnivorous ingestion of tissue
cysts can infect a naive host,
lead to nonsexual propagation.
Pathogenesis of Toxoplasmosis
• Chronic Bradyzoites (Cysts)
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• acute
Tachyzoites
Cell invasion
Symptoms
Toxoplasma infection is common, but
rarely produces symptoms in normal
individuals.
• In immunocompetent adults, it may
produce flu-like symptoms,
sometimes lymphadenopathy.
• In immunocompromised it results in
generalized parasitemia in brain,
liver lung and other organs, and
asymptomatic
• Adult infection
mild
symptomatic
severe
mild
• Intrauterine
Fever, pneumonia, hydrocephalus,
infection
microcephaly, encephalomyelitis
severe
Congenital infections occur in about
1-5 per 1000 pregnancies of
which:
• 5-10% result in miscarriage,
• 8-10% result in serious brain and
eye damage to the fetus,
• 10-13% of the babies will have
visual handicaps.
• Although 58-70% of infected
women will give a normal birth, a
small proportion of babies will
develop active retino-choroiditis or
Laboratory Diagnosis
• Sabin Feldman dye test
It is sensitive but requires use
of live toxoplasms ,not widely
used.
• In acute infection diagnosis
confirmed by identifying
toxoplasms in stained
preparations of:
Lymph node aspirates, CSF,
peritoneal aspirate, bone marrow
•Mouse inoculation by biopsy and
follow up for mouse to isolate
organism or demonstrate
seropositivity.
•Detection of parasitic genetic
material by PCR, especially in
detecting congenital infections in
utero.
Laboratory Diagnosis
Detect IgM and IgG
antibody
• Serologic test is the routine
method of diagnosis.
High antibody titer
particularly of IgM + raising
titer of IgG, must be
considered in relation to clinical
finding ,
• but interpretation of result is
difficult because high antibody
Treatment:
•Acute infections benefit
from pyrimethamine or
sulphadiazine. Spiramycin is a
successful alternative.
•Pregnant women are advised
to avoid cat litter, carefully
handling uncooked and
undercooked meat.
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