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AVBS3001- Parasitology > Toxoplasmosis: Protozoa > Flashcards

Toxoplasmosis: Protozoa Flashcards

1
Q

Characteristics of protozoa

A
  • single cell eukaryotes

- small (5-20um)

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2
Q

Trophozoite

A

any stage in protozoan’s life cycle which can ingest food (motile form)

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3
Q

Cyst

A

Non-motile form protected by distinct membrane or cyst wall (infective stage)

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4
Q

Excystation

A

process of emergence of trophozoite from cyst

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5
Q

Reproduction of protozoa

A

Asexual reproduction then sexual reproduction

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6
Q

Encystment of protoza

A
  • cysts forms

- resting stage w protective covering

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7
Q

Conditions for encystment

A
  1. loss of food source
  2. dessication
  3. increase in salt
  4. change in O2 conc
  5. change in pH
  6. temp change OR
  7. change in terminal stage of a life cycle
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8
Q

Process of encysting

A
  1. food is stored
  2. locomoter organelles absorbed
  3. nuclear division occurs
  4. cyst wall secreted
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9
Q

4 major groups of protozoa

A
  1. Amoeba
  2. Flagellae
  3. Cilia
  4. Apicomplexa
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10
Q

Neonate porcine coccidiosis

A
  • pale, watery diarrhoea
  • decreased growth
  • 5-15 day old piglets
  • high morbidity & low mortality
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11
Q

2-host life cycle of cyst forming coccidia (Neospora, Toxoplasma)

A
  1. Definitive host (predator) produces oocysts shed in env and picked up by intermediate host (prey)
  2. Asexual multiplication in intermediate host –> development of dormant cysts packed w infectious dose for definitive host
  3. these parasites can infect new intermediate host (omnivore) and skip definitive host route
  4. During acute phase of asexual multiplication the infection can spread throughout the host. If pregnant, infection will be transmitted to offspring–> abortion, stillbirth, congenital infection
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12
Q

Horizontal transmission

A

transmission of infection between hosts (not parent-child relo)

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13
Q

Vertical transmission

A

mother-child transmission during perinatal period

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14
Q

Foetal immunity vs Neospora caninum

A

Abortion incidence decreases w subsequent pregnancies–> maternal immunity matures after first pregnancy and influences outcome of subsequent pregnancies

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15
Q

Toxoplasmosis

A
  • congenital infection

- ingestion of infected meat followed by poor hygiene

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16
Q

Toxoplasma gondii

A
  • zoonotic

- heteroxenous, 2 host life cycle

17
Q

Definitive host of Toxoplasma gondii

A
  • cat (sexual reproduction in intestine)

- oocysts shed by cat are environmentally resistant

18
Q

Intermediate host of Toxoplasma gondii

A

all types of mammals and some birds

19
Q

Immunity against toxoplasma gondii

A
  • antibodies found in 30% of human population > 18yrs
  • antibody-mediated lysis of tachyzoites clears infection
  • recovery yields complete immunity
  • immunity can be boosted by tissue cyst breakdown
20
Q

Toxoplasma gondii: Epidemiology

A
  • reservoir is bradyzoite (cyst) in many animals and birds
  • cat only host w sexual stage; sheds from intestinal tract (main transmitters)
  • modes of transmission: fecal oral from cat, oral/raw meat, transplacental during acute infection
21
Q

Toxoplasma gondii epidemiology cont.

A
  • sandpits –> litterboxes–> infect children
  • oocysts must sporulate before becoming infectious
  • infectious cysts in meat can be killed by freezing
22
Q

Toxoplasma gondii can remain infectious for up to

A

2 years in suitable env (sandpit)

23
Q

Pathogenesis of Toxaoplasma gondii

A
  1. Acute infection
  2. Subacute infection
  3. Chronic infections
  4. Congenital toxoplasmosis
24
Q

Acute infection: toxoplasma gondii

A
  • often asymptomatic in cats but can kill kittens
  • humans have flu-like symptoms but immunity develops
  • Sheep & goats have abortion
25
Q

Subacute infection: toxoplasma gondii

A

hosts humoral immunity develops slowly.

Tachyzoites produce lesions in lung, liver, heart, brain, eyes

26
Q

Chronic infections

A

-Ab immune response depresses tachyzoites but cysts from bradyzoites cause intense inflammation, encephalitis, retinal degeneration, myocarditis

27
Q

Congenital toxoplasmosis

A
  • infection during preg can infect foetus, cause still birth, abortion, birth defects
  • hydrocephaly, microcephaly, blindness

AVBS3001- Parasitology (11 decks)

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