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(3002) Clinical Micro > Parasitology > Flashcards

Parasitology Flashcards

1
Q

In host parasite relationships, what is the difference between the terms definitive host and intermediate host?

A
  1. Definitive host: animal where parasite develops into adulthood &/ undergo sexual REPRO. phase
  2. Intermediate host: short-term host (parasite not grow till adult & NO repro. phase)
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2
Q

What is an ectoparasite? What is an endoparasite? Give examples.

A
  • Ectoparasite: parasite that lives on/close to the surface of the host e.g. lice, scabies (burrow in epidermis)
  • Endoparasite: parasite that lives (deep) inside the host e.g. tapeworm
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3
Q

List 5 ways that a parasite can harm a host?

A
  1. mechanical inquiry e.g. attach to mucosa
  2. Obstruction
  3. produce metabolic products = toxic to host
  4. competing w/ host for nutrients
  5. Host IR when parasite dies = inflammation
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4
Q

List 4 ways that a parasite may gain entry to the host?

A
  • Oral (bc poor food hygiene)
  • percutaneous (penetrate through soft skin
  • Inhalation (of eggs)
  • Sexual intercourse
    ~ Intraplacenta (applicable to bact.)
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5
Q

Define the three types of specificity required for a human parasite to become established in vivo.

A
  1. Ecological specficity: external environment allow for survival of infective form
  2. Ethological specificity: human behaviour in that environment allows parasitic stage to enter human tissues
  3. Physiological specificity: the potential host’s internal environment suitable for development of parasite
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6
Q

Give an example of a geographical factor that can affect the distribution of parasites?

A
  • Climate
  • Soil type
  • Coprozoic organisms (digest poo e.g. earth worms)
  • surface water
  • vegetation
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7
Q

Which common protozoan parasite is responsible for causing diarrhoea, mucus secretion and flatulence

A

Giardia lamblia

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8
Q

What is the rostellum?

A

is the “beak” that hooks onto the host’s intestinal walls - using the hooks. Located at the apical of the scolex (head)

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9
Q

Some parasitic eggs (ova) look very similar. How could you decide which parasite they belong to in a clinical laboratory?

A
  • Consider the size

- Use fine focus to detect other potential features like peritrichous flagella

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10
Q

Draw a lifecycle of Taenia sp.

A
  1. Cattle (T.saginata) & pigs (T.solium) eat eggs or gravid proglottids in contaminated vegetation
  2. Oncospheres hatch penetrate intestinal wall & circulate to muscle
  3. Cyst develop in muscle (infective stage)
  4. Humans eat raw/undercooked infected meat
  5. Taenia sp. develop in gut
  6. reproduce releasing eggs/proglottids in poo (diagnostic)
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11
Q

List the scientific group names for the three categories of worms/helminths (flukes, tapeworms and roundworms)?

A
  1. Platyhelminths (flatworms):
    - Trematodes (flukes)
    - Cestodes (tapeworms)
  2. Nematodes (roundworms)
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12
Q

What is the common name for:

a) Enterobius vermicularis
b) Trichuris trichiura
c) Ascaris lumbricoides
d) Hookworms
e) Strongyloides stercoralis

A

a) E.vernicularis: Pin worm or thread worm
b) T.trichiura: whipworm
c) A.lumbricoides: round worm
d) Hookworms: New & Old world
e) Strongyloides stercoralis (no common name)

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13
Q

Draw a simple lifecycle diagram for Enterobius vermicularis.

A
  1. Female worms lays eggs on perineal folds (diagnostic stage)
  2. Embryonated eggs ingested/inhaled by human (usually scratching butt) (infective stage)
  3. larvae hatch in sml int. & grow to adulthood in colon
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14
Q

Draw a simple lifecycle diagram for Ascaris lumbricoides

A
  1. Human poo contains (un- and) fertilised eggs. Fertilised eggs become infected in soil (infective phase)
  2. human ingests fertilised eggs from soil-contaminated hands/food
  3. larvae hatch in sml GIT & Penetrate mucosa into blood -> lungs
  4. mature in lungs 10-14 days then ascend bronchial tree to be swallowed
  5. mature in sml int. (diagnostic)
  6. Adult female lays eggs 2-3 months after infection
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15
Q

In the lifecycle of Clonorchis sinensis, what are the names of each of the parasitic stages of development that occur after the egg hatches until ingestion?

A
  1. Embryonated eggs passed in poo (diagnostic)
  2. Eggs ingested by freshwater snail & develop: miracidia > Sporocysts > Rediae > Cercariae
  3. Cercariae swim freely in water & can penetrate skin or flesh of fish
  4. Metacercariae ingested when eat raw freshwater fish (infective)
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16
Q

a) What is the diagnostic form of Strongyloides stercoralis?
b) Why are eggs not usually seen in faeces?

A

a) Rhabditiform larvae in stool (180-380 ug long).

b) Eggs not seen in poo bc eggs secreted in intestinal mucosa and hatch

17
Q

Which parasites in this lecture are capable of autoinfection?

A
  • Strongyloides stercoralis
  • Hymenolepis nana
  • not need to exit into environment
18
Q

How can you differentiate between T.saginata and T.solium in the clinical laboratory?

A

By examining the proglottids or scolex.
T.saginata: Tall & skinny uterine tubes in proglottids
T.solium: short & thick uterine tubes in proglottids

19
Q

Describe what cysticercosis is and how this is different from the normal infection caused by the cestode responsible?

A

Cysticerosiss: Human ingest the embryonated egg -> oncospheres hatch & penetrate intestinal wall into circulation -> develop in any organ (e.g. brain)
Normal: oncopheres usually hatch in GIT of pig & circulate to muscles -> human ingest cysterci in pig muscle

20
Q

Give an example of a socio-economic factor that can affect the distribution of parasites?

A
  • Housing
  • Coprophagic animals
  • Urbanisation
  • Economic activities
  • Domestication of animals
  • Migration, war, tourism
21
Q

Draw a simple lifecycle diagram for Hookworms.

A
  1. Eggs in faeces (diagnostic)
  2. Rhabditoform larva hatches in soil & develops into filariform larvae after 5-10 days
  3. Filariform larvae penetrates skin (infective)
22
Q

For Fasciola hepatica name the:

a) diagnostic form
b) infective form
c) if applicable, name the type of intermediate host

A

a) diagnostic: unembryonated eggs in poo
b) infective: metacercariae
c) intermediate host: (water) snail

23
Q

For Clonorchis sinensis name the:

a) diagnostic form
b) infective form
c) if applicable, name the type of intermediate host

A

a) diagnostic: embryonated eggs in poo
b) infective: metacercariae in flesh/skin of fish
c) intermediate host: freshwater snail

24
Q

For Schistosomiasis sp. name the:

a) diagnostic form
b) infective form
c) if applicable, name the type of intermediate host

A

a) diagnostic: eggs in urine
b) infective: cercariae (free-swimming)
c) intermediate host: freshwater snail

25
Q

For Hymenolepis nana name the:

a) diagnostic form
b) infective form
c) if applicable, name the type of intermediate host

A

a) diagnostic: embryonated eggs in poo
b) infective: embryonated eggs in poo
c) intermediate host: can have = insects)

26
Q

For Taenia sp. name the:

a) diagnostic form
b) infective form
c) if applicable, name the type of intermediate host

A

a) diagnostic: embryonated eggs in poo
b) infective: embryonated eggs in poo
c) intermediate host: pig (T.solium) & cattle (T.saginata)

27
Q

For Echinococcus granulosus name the:

a) diagnostic form
b) infective form
c) if applicable, name the type of intermediate host

A

a) diagnostic: hyatid cysts in liver, lung
b) infective: embryonated eggs in poo
c) intermediate host: sheep, goats
* human accidental hosts)

28
Q

For Trichuris trichuria name the:

a) diagnostic form
b) infective form
c) if applicable, name the type of intermediate host

A

a) diagnostic: unembryonated eggs in poo
b) infective: embryonated eggs
c) intermediate host: n/a

29
Q

For Dracunculus medinensis name the:

a) diagnostic form
b) infective form
c) if applicable, name the type of intermediate host

A

a) diagnostic: L3 larvae in copepod in water
b) infective: embryonated eggs
c) intermediate host: copepod

30
Q

For Giardia lamblia name the:

a) diagnostic form
b) infective form
c) if applicable, name the type of intermediate host

A

a) diagnostic: cysts & trophozoites in poo
b) infective: cysts in poo
c) intermediate host: n/a

(3002) Clinical Micro (19 decks)

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