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PARA434 > Lecture 5: Toxoplasma > Flashcards

Lecture 5: Toxoplasma Flashcards

1
Q

who can be the intermediate host?

A

anyone can be an intermediate host: cow, chicken, frog, fish, etc.

not just mammals

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2
Q

what does someone infected with toxoplasma gondii have?

A

toxoplasmosis

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3
Q

can toxoplasma gondii infect fetus?

A

yes this parasite can infect a fetus

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4
Q

what is the distribution of toxoplasma gondii in developed vs less developed countries?

A

DEVELOPED COUNTRIES
- the younger you are, the less likely you are infected with toxo (likelihood of infection increases by age)
- peak at 25 because when you get older, you start to experiment more in food. if the food is raw, you are more likely to get toxo.

LESS DEVELOPED COUNTRIES
- due to the environment
- there are areas with a lot of stray cats, and children play outside and expose themselves
- eat m ore raw meat.

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5
Q

What are the 2 hosts required for the life cycle of toxoplasma gondii (the definitive and intermediate hosts)

How does each host get infected with Toxo?

A

Definitive host
- Domestic and wild cats. ALWAYS FELINE
- They get infected by ingesting sporulates oocysts or infected rodents or birds.

Intermediate host (reservoir host)
- Most species of warm-blooded animals, including birds, mice, squirrels, rabbits, cattle, pigs, sheet, fish, etc.
Humans get infected by ingesting the oocyte, eating raw meat, transplacentally or organ transpantations.

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6
Q

what are the two phases of the life cycle in toxo?

A

intestinal phase: (occurs only in wild or domestic cats) and produces oocysts

extra-intestinal phage: (occurs in all infected animals and produces tachyzoites, eventually bradyzoites)

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7
Q

What is the life cycle of toxoplasma gondii in the definitive host?

A

cat is infected by:

  1. eating OOCYST in cat feces
    OR
  2. eating an intermediate host like a mouse containing BRADYZOITES

the oocyst develops into sporozoites. the sporozoites and the bradyzoites can penetrate the SMALL INTESTINE

will differentiate into trophozoite, and eventually merozoites from binary fission/schizogony.

it will re-invade the small intestine and turn into gametocytes (sexual form) where theyll differentiate into microgamete (male) and macrogamete (female)

microgamete and macrogamete form a ZYGOTE.

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8
Q

what is the life cycle of toxoplasma gondii in the intermediate host?

A

vertebrate will become infected by ingesting oocyst or ingesting raw/poorly cooked intermediate host containing bradyzoites

oocysts differentiate into sporozoite in 2-3 days and then penetrate any nucleated body cell to become tachyzoites. whereas bradyzoites immediately penetrate body cell and become tachyzoites. (RAPID MULTIPLICATION)

they eventually become bradyzoites (SLOW MULTIPLICATION) as host builds up immunity.

bradyzoites are infective to cat and humans.

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9
Q

EXPLAIN THE FULL LIFE CYCLE OF TAXOPLASMA GONDII

A
  1. immature oocyst is shed in cat feces
  2. mature oocyst develops by sporogony and contains two sporocysts, each with four infective sporozoites
  3. oocysts can infect many hosts, including mice, domestic animals, and humans via ingestion
  4. sporozoites from ingested oocists invade animal tissue and develop into bradyzoites within tissue cysts or into tissue-invading tachyzoites
  5. cat ingests bradyzoites in tissue cysts in animals, usually mice
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10
Q

EXPLAIN THE FULL LIFE CYCLE OF TAXOPLASMA GONDII

A
  1. immature oocyst is shed in cat feces
  2. mature oocyst develops by sporogony and contains two sporocysts, each with four infective sporozoites
  3. oocysts can infect many hosts, including mice, domestic animals, and humans via ingestion
  4. sporozoites from ingested oocists invade animal tissue and develop into bradyzoites within tissue cysts or into tissue-invading tachyzoites
  5. cat ingests bradyzoites in tissue cysts in animals, usually mice
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11
Q

which are the infective stages of toxoplasma gondii?

A

all stages are the infective stages (oocyst, bradyzoites, tachyzoites)

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12
Q

what is it called when you develop sickness from taxoplasma gondii?

A

toxoplasmosis

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13
Q

what are the three forms that toxoplasma gondii exist in?

A
  1. oocysts
  2. tachyzoites
  3. bradyzoites (tissue cysts)
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14
Q

Toxoplasma gondii - oocyst … where do they normally come from?

A
  • Infected cats shed oocysts for only 1-2 weeks following parasite infection
  • They sporulate and become infective after 2 days

-Remain viable in the soil for YEARS

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15
Q

Define the oocyst (what does it look like)

A
  • The oocyst contains two sporocysts
  • Each sporocyst contains 4 sporozoites.
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16
Q

What are toxoplasms gondii tachyzoites? What phage of infection? Sexual or asexual form?

A
  • Intracellular parasites enclosed in a parasite membrane to
    form a cyst
  • It marks the acute phase of infection

-Asexual form

17
Q

what does a tachyzoite look like? where is the apical complex?

A

has an apical complex at the top

18
Q

what are bradyzoites in toxoplasma gondii

A
  • tissue cysts

-occurs as a circular mass in body cells

  • contains thousands of parasites and remains in the tissue, especially brain, heart, skeletal muscles, etc.
  • marks the chronic phase of infection

-will remain in host for rest of life

-resistant to low pH and digestive enzymes during stomach passage

19
Q

how can you get infected with toxoplasma gondii

A
  • eating raw/undercooked meat of animals
    -consuming food/water with contaminated oocysts
    -blood transfusion or organ transplantation
    -transplacental from mother to fetus
20
Q

how to prevent infection of toxoplasma gondii

A

-wash hands and countertop after preparing raw meat/fish

-thoroughly cook meat

-clean liter box daily (since it takes 2 days for the oocysts to sporulate and become infective)

-feed cat commercial dry food, never raw meat

  • cover outdoor sandbox to prevent cats from leaving feces in there.
21
Q

toxoplasma gondii clinical disease in cats

A
  • infection is asymptomatic
  • acute infections result in numerous intestinal lesions that can rarely kill kittens
22
Q

toxoplasma gondii - clinical disease in humans

A

IN IMMUNO-COMPETENT INDIVIDUALS ITS ASYMPTOMATIC
- clinical course is benign and self limited. symptoms resolve in a few weeks/ months

  • mild fever, sore muscles, swollen glands, lymph nodes

IN IMMUNO DEFICIENT INDIVIDUALS: GREATER RIISK
- often have central nervous system disease

  • in AIDS , most common cause of intra cerebral mass lesions and is thought to be caused by reactivation of chronic infection.
23
Q

Toxoplasma gondii - clinical disease in pregnant women

A
  • pregnant women’s fetus are at risk if the mother acquires the infection for the first time during gestation
24
Q

how is toxoplasma parasites transmitted to fetus?

A

transplacental to the fetus (called congenital toxoplasmosis), resulting in spontaneous abortion, a still born, or a child that is severely handicapped mentally and/or physically

25
Q

what will congenital toxoplasmosis lead to in fetus?

A
  • chorioretinitis (leads to blindness): ocular disease is the most common
  • hydrocephaly: least common but most dramatic lesion.
26
Q

how is toxoplasma gondii diagnosed?

A
  • ELISA tests (serological testing)
  • test amniotic/spinal fluid isolation and culture of parasite
  • microscopy/ PCR
27
Q

explain the results of sabin-feldman dye test to test for taxoplasma gondii

A
  • live virulent tachyzoites of t gondii are used as antigen and are exposed to dilutions of the patients serum
  • if you have antibodies, it will bind to it and turn a fluorescent green, indicating that you were infected with the parasite.
28
Q

toxoplasma gondii - behaviour change (MANIPULATION HYPOTHESIS)

A
  • parasites manipulate host behaviour to enhance their own fitness
  • changes in host behaviour may result in immunological or pathological consequences of parasite infection
  • for example, the mouse infected with toxo needs to be in vicinity of cat for the life cycle to continue (the cat needs to be in reproductive stage).
  • the mouse developed loss of fear towards cat urine! attracts them to cats more so they can be eaten by cats, to complete life cycle of toxoplasma gondii
  • called the MANIPULATION HYPOTHESIS

PARA434 (6 decks)

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