Toxoplasmosis Flashcards
true or false: toxo is a protozoa
true
true or false: toxo is a coccidia, microsporidia
-false
coccidia, sporozoa, microsporidia
true or false: toxo gondii is a food and waterborn parasite
true
toxo gondii: development of oocysts that are shed with…..
the defenitive host feces and contaminate the environment
when was toxo gondii first described and by who
1908 in Tunis by Nicolle and
Manceaux in the gundi, which is an African rodent
when was toxo gondii named
1909
true or false: several decades passed before we knew what toxo gondii di to humans
yeah
when was the standard test developed for giardia
1948, serological dye test
when was the life cycle for giardia first described and why who
start of 1970’s by frenkel and hutchinson
which parasite uses 2 sets of hosts for the completion of its life cycle
toxo
what are the 2 life cycle of toxo and it infects what
-1. ASEXUAL CYCLE IN
“INTERMEDIATE” HOSTS
Humans, cattle, rodents, pigs,
sheep, cats, etc
(all warm-blooded vertebrates)
-2. SEXUAL CYCLE IN
“DEFINITIVE” HOSTS
Cats and other Felids
via carnivorism / predation
which steps of toxo are in the asexual cycle
- Tachyzoites
- Bradyzoites in tissue cysts
which steps of toxo are in the sexual life cycle
- Macro- and microgametes
- Sporozoites in oocysts
contamination of toxo occurs mostky how
-oral route
-ingestion of raw or partly cooked meat like pork, lamb or venison who contain tissue cyst (bradyzoites)
-ingestion of oocyst contaminated cat feces through hand to mouth contact
-drinking water contaminated with oocysts
-transplacental infection in utero (tachyzoites)
-transplantation of an infected organ (bradyzoites in tissue cyst)
prevalence of toxo in humans
-up to 60% of the human population is seropositive
-Up to 60% in Québec (especially Nunavik Inuit), Nunavut, Western Europe
-depends on food habits and contact with cats
prevalence of toxo in animals
- ~ 10% in pork
- ~ 40% in sheep/lamb
- 20-63% in goats
true or false: toxoplasmosis is usually benign
trye
how many peeps are infected by toxo
30-60% are infected
why is toxo mostly benign
because the immune response is super efficient
when are symptoms for acute toxoplasmosis show usually
1-3 weeks post infection
what is the acute stage of toxo
virulent tachyzoites
The acute stage (virulent tachyzoites) fades in a few days to weeks, leading to ……
the latent stage of the infection aka bradyzoite tissue cysts which is normally asymptomatic
when is toxo benign
-aids peeps
-during pregnancy
aids patients: toxo
toxoplasmosis can develop. The most notable manifestation is toxoplasmic encephalitis, which is fatal without drug treatment.
primary infection of toxo during pregnancy
possibly leading to hydrocephaly, microcephaly, intracranial calcification, and
chorioretinitis, with the possibility of miscarriage or intrauterine death. Ocular toxoplasmosis
may develop later in life.
infection of toxo during 1st trimester
incidence of transplacental infection is low (15%) but the disease in neonates is most severe.
infection of toxo during 3rd trimester:
– the incidence of transplacental infection is high (65%) but the infant
is usually asymptomatic at birth.
what is the symptomatic phase of toxo in aids
Symptomatic phase when CD4+ T cell count < 200 cells/µl due to tissue cyst
reactivation – toxoplasmic encephalitis (TE)
true or false: the tachyzoite of toxo is the acute phase of toxo
it is the acute/invasive/proliferatibe stage
what are the rhoptries in toxo
unique secretory/excretory
organelles found exclusively in the Apicomplexa.
-Important at the time of invasion and critical in the
establishment of a
productive infection
what are dense granules
secrete their contents during and after invation
-major t cell antigen for class 1 mhc
true or false: in toxo they have stage specific surface antigens
-true they are known as adhesins
in toxo: GPI-anchored proteins, which act as redundant
receptors for binding to…
sulf proteoglycans on various host cells
what is the dormant stage of toxo
-the bradyzoite
-aka the dormant stage
true or false: bradyzoite looks like tachyzoite
true
-But distinct antigenically and physiologically (different set of SAG surface antigens)
what are the reserve of carbohydrates for toxo
amylopectin granules
bradyzoites of toxo live where and are derived from what
- in tissue cysts,w hich are derived from a parasitophorous vacuole and a cyst wall
how big are bradyzoites
10-200 um
the dormant stahe of toxo is found where
found in muscles (infective stage), brain
unlike tachyzoite in toxo, bradyzoites are resistant to what
low ph and host digestive proteases in the stomach
The transition from tachyzoite to bradyzoite is associated with morphological changes:….
narrowing of the parasite body, movement of the nucleus toward the parasite posterior, an increase in
the number of micronemes (blue) and amylopectin granules (white), and more electron-dense
rhoptries (maroon).
one stress response pathway in toxo linked to stage conversion involves what
phosphorylation of the alpha subunit of eukaryotic initiation factor-2 (TgIF2α), which is mediated by stress-activated TgIF2α kinases (TgIF2Ks).
what is the sexual stage for toxo
the sporozoite/oocyst
how big is the toxo ooxyst
13um in size
the oocyst of toxo is resistant stage viable in moist soil for …
18 months
the oocyst is a product of what
-product of sexual cycle (micro- and macrogametes), which occurs in the intestinal cells
of definitive hosts (cats)
oocyst in toxo are passed out in the feces of …
s by definitive
hosts/carnivores (cat) feces-10-14 days after infection
true or false: in toxo, each oocysts contain 4 sporocysts
false, it is 2
true or false: oocysts are infective to humans and other herbivore hosts
true
oocysts of toxo are resistant to what
Physical agents
UV, dessication, freezing
Chemical agents
Ozone, bleach, iodine, ethanol, formalin, salts
persistence of oocysts toxo
18 months in soil
54 months in water
true or false: is unsporulated and non-infectious when excreted
true
what do toxo oocysts contain
it contains a single, undifferentiated cytoplasmic mass and is essentially the zygote stage of the parasite surrounded by a protective
wall
in toxo: sporulation occurs by what
meiotic division
meotic division in toxo oocysts
During this process, the cytoplasm divides into a characteristic number of sub-masses (secondary
sporoblasts), which develop a resistant wall and are termed sporocysts. Within the sporocysts, the infectious stages (sporozoites) are formed. The sporozoites are thus protected by both the oocyst and sporocyst walls
how many sporozoites are in a sporocyst
4
true or false: can shed oocysts in their feces for several weeks after the initial contamination
true
how long do oocysts of toxo can become infectuous
1-2 days
how many % of cats shed oocyst at any one time
2%
oocyst of toxo shedding does not recur after….
even after repeated exposure to the parasite
true or false: toxo oocysts have been detected on cat fur and in their infectuous form
false: in their non infectuous form
when was the outbreak of toxo in bc
1995 on vancouver island
which parasite is a significant cause of death of sea otters
toxo
-38% of lil sea otters had toxo
true or false: toxo is a threat for the safety of public water supplies
true
what is the type of immune response to toxo
controlled by cell mediated immunity
-cd8 are the major effectors
-cd4 are important for regulation of immune response
-nk and macrophages are the first line of defense
what cytokine is important for th1 response to toxo gondii
il12
-you also have infy to kill intracellular parasites
true or false: it is hard to show that someone is infected by toxo
yeah because it is intracellular
how is toxo diagnosed
Acute infection is assessed by serology (IgG & IgM)
IgG antibodies usually appear 1 to 2 weeks after the
initiation of infection, reaching peak titers in 6 to 8 weeks,
then gradually decline over 1 to 2 years.
how are the titers for toxo
-usually low
-persists for life
true or false: toxo titers correlates with disease severity
false it does not
how is acute infection of toxo diagnosed?
-serology
-elisas are available and now preferred
intra-uterine and cerebral disease of toxo can be diagnosed how
pcr
treatment of toxo acute
-pyrimethamine
-sulfadiazine
-clindamycin
-spiramycin
treatment of toxo chronic
-tissue cyst are resistant to most treatment
-atovaquone
-clindamycin
why is toxo so sucessful
-it is protected from many immune effector mechanisms because it is intracellular
-can infect any nucleated cell in any warm blooded vertebrate
the vacuole of toxo are resistant to what
fusion with the host cell lysosomes
true or false: t gondii manipulated host cell processes
true
what does T gondii manipulate
host cells and immune effectors
why are toxo hosts rarely killed
A balanced host-parasite interaction is established
and is necessary for T. gondii survival, persistence and transmission
