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HMS116: Microbiology & Immunology > Parasites > Flashcards

Parasites Flashcards

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Biology 101 flashcards
1
Q

Source of infected patients?

A
  • missionaries
  • Peace Corps volunteers
  • tourists
  • increasing number of refugees (developing countries)
  • immunosupressed patients
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2
Q

Where are diseases caused by parasites usually found?

A
  • tropics
  • subtropics
  • more temperate climates
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3
Q

Most common parasitic infection?

A
  • Trichomonas
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4
Q

Parasitic disease that is a frequent cause of recreational water-related disease outbreaks?

A
  • Cryptosporidiosis
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5
Q

Cyst definition

A
  • thick-walled, resistant and resting cell
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6
Q

Trophozoite definition

A
  • active, feeding and multiplying stage of most protozoa
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7
Q

Oocyte definition

A
  • zygotic cyst
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8
Q

Schizogony definiton

A
  • asexual reproductive stage of parasite (sporozoite stage)
  • multiple fission: nucleus divides then cell divides into as many parts as there are nuclei
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9
Q

Vector definition

A
  • living organisms carrying pathogen to new host
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10
Q

Intermediate host definition

A
  • hosts immature form of the parasite
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11
Q

Definitive host definition

A
  • hosts mature form of the parasite
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12
Q

Classifications of parasites

A
  • protozoa
  • helminths
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13
Q

Protozoa

A
  • microscopic unicellular eukaryotes with complex internal structures

: Flagellates

: Amoeba (Rhizopods)

: Ciliates

: Sporozoa (Apicomplexa)

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14
Q

Helminths

A
  • worm-like parasites

: trematodes

: cestodes

: nematodes

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15
Q

Parasite life cycles

A
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16
Q

Protozoa: classification and morphology

A
  • many have typical eukaryotic organelles
  • membrane-bound nucleus (contains chromosomes)
  • endoplasm & ectoplasm
  • variety of morphologies
  • usually in moist environments
  • obtain nutrients from environment
  • cytosome mouth can ingest food
17
Q

Motility of Protozoa: flagella

A
  • one or few flagella
  • wave-like beat
  • can form undulating membranes
    e. g. flagellates
18
Q

Motility of Protozoa: Cilia

A
  • usually covers protozoa
  • coordinated; function like oars to propel
    e. g. ciliates
19
Q

Motility of Protozoa: gliding motility

A
  • glides
    e. g. Plasmodium species
20
Q

Motility of Protozoa: Ameboid movement- crawling

A
  • Pseudopodium attach to surface and pull forward
  • force generated by cytoskeletal system composed of actin & myosin
    e. g. Entamoeba histolytica

: inhabits human colon and causes human dysentry (bloody diarrhea)

21
Q

Protozoa asexual reproduction

A

asexual reproduction

  • binary fission, budding
  • multiple fission or segmentation
  • several rounds of nuclear replication occur without cytokinesis
  • formed multinucleated cell produces multiple progeny simultaneously
22
Q

Protozoa sexual reproduction

A
  • production and fusion of gametes
23
Q

Helminth: classification and morphology

A
  • worm-like parasites
  • multicellular with complex reproductive systems and life cycles involving intermediate hosts and a definitive host
  • tough outer cuticle
  • Nematodes: roundworms
  • Cestodes: tapeworms
  • Trematodes: flukes
24
Q

Helminths: flukes

A
  • trematode
  • adult flukes are leaf-shaped flatworms
  • bind pocket alimentary tract
  • prominent oral and side suckers
  • hermaphroditic (except blood flukes- bisexual)
  • life-cycle includes mollusks (snails and clams) as intermediate hosts
25
Q

Helminths: tapeworms

A
  • cestodes
  • adult tapeworms are elongated & segmented
  • hermaphroditic flatworms inhabit intestinals
  • larval forms inhabit extra-intestinal tissues
  • head (scolex) of worm usually has 4 muscular cup-shaped suckers and crown of hooklets
  • individual tapeworm segments are proglottids
  • chain of proglottids is called a strobila
  • end part of proglottides are almost completely made up of a uterus full of eggs
26
Q

Proglottids definition

A
  • individual tapeworm segments
27
Q

Strobila definition

A
  • chain of proglottids
28
Q

Helminths: Roundworms

A
  • nematodes
  • adult & larval roundworms are bisexual and cylindrical
  • inhabit intestinal and extra-intestinal sites
  • large sites
  • live primarily as adult worms in intestinal tract, and infections most commonly confirmed by detecting eggs in the feces

: can infect the blood and tissues too

29
Q

Parasite pathogenicity

A

EAR D DIE

1. Entry & Exposure Route

2. Attachment

3. Replication

4. Damage- cell & tissue

5. Disruption, envaion and inactivation of host defences

30
Q

Parasite pathogenicity: Entry and Exposure Route

A
  • exogenous source

: ingestion

: direct penetration of anatomical barriers

: bites of anthropod vectors

  • infective does and exposure
31
Q

Parasite pathogenicity: Attachment

A
  • can be non-specific
  • mechanical or biting mouthparts
  • parasite adhesins
  • distinguishes pathogenic from nonpathogenic strains
32
Q

Parasite pathogenicity: replication

A
  • protozoa replication can occur intracellularly or extracellularly in human host
  • helminth replication is generally not observed
33
Q

Parasite pathogenicity: Damage- cell & tissue

A
  • toxic products (proteases and phospholipases)
  • mechanical tissue damage (migration, blockage)
  • immunopathological reactions (hypersensitivity)
  • longevity
34
Q

Parasite pathogenicity: Disruption, evasion and inactivation of host defense

A
  • antigenic variation/ shift in antigenic expression
  • intracellular expression
35
Q

Laboratory Parasitology: Diagnosis

A
  • Helminth diseases: peripheral eosinophilia recognized as useful indicator of parasitic disease
  • rely on detailed travel, food intake, transfusion history
  • Lab techniques

: isolate appropriate specimen

: macro- & microscopy: morphology

: serology

: detection of parasitic antigen

: PCR

36
Q

Laboratory Parasitology: Importance of Life Cycles

A
  • features of parasitic life cycles must be considered for proper diagnosis

: eggs vs larvae

: nocturnal

: life cycle stages may result in certain clinical manifestations in the host

HMS116: Microbiology & Immunology (16 decks)

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