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Microbiology > Parasites > Flashcards

Parasites Flashcards

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Biology 101 flashcards
1
Q

Define parasitism.

A

Metabolic dependence on host. Requires nutrients/stimuli from the host to the detriment of the host

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2
Q

Define commensalism.

A

No metabolic dependence. One partner benefits, the other is disadvantaged/not effected

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3
Q

Define mutualism.

A

No metabolic dependence. Both partners benefit

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4
Q

Define parasite.

A

An organism which lives on or in another organism ‘host’ and benefits by deriving nutrients at the host’s expense

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5
Q

What defines an organism as protozoa? Name four species

A

Unicellular parasite.

  1. Amoebae
  2. Flagellates
  3. Apicomplexa
  4. Ciliates
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6
Q

What defines an organism as metazoa? Name two species and any sub-species

A

Multicellular parasite.

  1. Plathelminths (flat worms)
    - Cestodes (tape worm)
    - Trematodes (fluke)
  2. Nematohelminths (round worms)
    - Nematodes (round worm)
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7
Q

What is a direct life-cycle?

A

Transmission from one host to another host of the same species

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8
Q

What is an indirect life-cycle?

A

Transmission wherein the life-cycle involves 2+ hosts of different species

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9
Q

What is a definitive host?

A

The host in which the the sexual reproduction of the parasite occurs

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10
Q

What is an intermediate host?

A

The host in which only asexual reproduction occurs and the larve stage is present

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11
Q

What is an accidental host?

A

The host is considered the ‘dead-end host’ as it is not the normal host and the parasite cannot complete it’s life-cycle

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12
Q

What is a vector?

A

An organism that conveys the parasite from one host to another host

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13
Q

What is a biological vector?

A

A vector wherein the parasite undergoes further development (eg: Anopheles mosquito)

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14
Q

What is a mechanical vector?

A

A vector wherein the parasite undergoes no further development (eg: flies)

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15
Q

What type of life-cycle does an Amoeba have?

A

Direct life-cycle

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16
Q

Briefly describe the amoeba life-cycle.

A

2 stages.

  1. Trophozoite (motile, feeding, binary fission)
  2. Cyst (infective for humans)
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17
Q

How are amoebae transmitted?

A

Direct faeco-oral transmission (contaminated food/water)

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18
Q

What is the pathogenesis of amoebae?

A
  • Excystation in intestine followed by multiplication

- Trophozoites adhere to large intestine epithelium (disrupts the epithelial barrier and results in invasion)

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19
Q

What disease do amoebae cause in humans?

A
  • Assymptomatic
  • Dysentry (inflammation of intestine = diarrhoea with blood)
  • Flask-shaped ulcers
  • Hepatic and lung abscesses
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20
Q

Which species of direct apicomplexa causes disease in humans?

A

Intestinal Cryptosporidium

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21
Q

What type of life-cycle do apicomplexa have?

A

Direct and indirect life-cycle

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22
Q

Briefly describe the direct apicomplexa life-cycle.

A
  • Entire life-cycle can occur in 1 host
    1. Low infection dose with thick-walled oocyte
    2. Excystation of oocyst in duodenum releasing sporozoites (which bind and invade intestinal epithelial cells)
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23
Q

How are direct apicomplexa transmitted?

A

Direct faeco-oral transmission (contaminated food/water)

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24
Q

What is the pathogenesis of direct apicomplexa?

A
  • Intestinal disease (intestinal epithelium death > villous atrophy > impaired intestinal absorption)
  • Extra-intestinal disease (immunocomprimised patients develop biliary and respiratory tract infections)
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25
Q

What disease do direct apicomplexa cause in humans?

A
  • Self-limiting diarrhoea
  • Significant malabsorption
  • Fluid and electrolyte imbalances
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26
Q

How is an direct apicomplexa infestation diagnosed?

A

Stool microscopy

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27
Q

How is an direct apicomplexa infestation managed?

A
  • Supportive fluid electrolyte therapy
  • HAART (HIV patients)
  • Co-trimoxazole
28
Q

Which species of indirect apicomplexa causes disease in humans?

A

Toxoplasma gondii

29
Q

Briefly describe the indirect apicomplexa life-cycle.

A
  • Definitive host = cats
  • Intermediate host = humans / warm blooded animals
  1. Oocyst containing sporozoites
  2. Cresant shaped tachyzoite (motile and replicate)
  3. Tissue cyst containing bradyzoites (dormant)
30
Q

How are indirect apicomplexa transmitted?

A
  • Ingestion of oocyst shed in cat faeces
  • Ingestion of raw meat containing cyst with bradyzoite
  • Congenital transmission (transplacental)
  • Organ transplant, blood transfusion or needle-stick injury
31
Q

What disease do indirect apicomplexa cause in humans?

A
  • Immunocompetent: low grade fever, flu-like symptoms

- Immunocomprimised: disseminated disease, fever, myositis, CNS involvement

32
Q

How is an indirect apicomplexa infestation diagnosed?

A
  • Serology
  • Radiology
  • Histopathology
  • Molecular testing
33
Q

How is an indirect apicomplexa infestation managed?

A
  1. Folic-acid antagonists:
    - pyrimethamine-sulfadiazine
    - trimethoprim-sulfamethoxazole
  2. Prophylaxis for immunocomprimised
34
Q

What aids the prevention of an intestinal nematode infection?

A
  • Hygiene and sanitation (handwashing)
  • Avoid soil pollution (faecal matter)
  • Avoid use of night soil
  • Mass treatment of families / school children
35
Q

What is the recommended treatment for an intestinal nematode infection?

A
  1. Mebendazole / Albendazole
36
Q

What life-cycle do nematodes (roundworms) have?

A

Direct life-cyle

37
Q

What is the transmission of nematodes?

A
  • Ingestion of embryonated ova

- In-tact skin penetration by infective (filariform) larvae

38
Q

What general structure do nematodes have?

A
  • Cylindrical body cavities

- Seperate sexes

39
Q

What disease does Ascaris lumbricaides cause?

A
  • Migration of larvae: Loeffler’s Syndrome (heart-lung migration)
  • Migration of adults: mouth and anus
  • Adults in small intestinal: lumen obstruction (malnutrition)
40
Q

How is Ascaris lumbricoides diagnosed?

A
  • Stool microscopy (ova)

- Identify adult worms passed

41
Q

Name two hookworm species.

A
  1. Ancylostoma duodenale

2. Necator americanus

42
Q

What is the pathogenesis of a hookworm infestation?

A
  • Migration of larvae: heart-lung

- Adults attach to small intestine mucosa and feed on blood (cause anaemia)

43
Q

What disease do hookworms cause in humans?

A
  • Ground itch: larval skin penetration
  • Loeffler’s Syndrome
  • Intestinal worms: abdominal pain, weight-loss, anaemia, hypoproteinaemia
44
Q

How is a hookworm infestation diagnosed?

A
  • Stool microscopy (ova)
45
Q

What does the parasitic life-cycle form of Strongyloides Stercoralis (nematode) entail?

A

Adult female > duodenal mucosa where eggs hatch
Larvae in faeces
Filariform larvae in soil

46
Q

What does the free living life-cycle form of Strongyloides Stercoralis (nematode) entail?

A

Male and female mate

Eggs hatch and develop into larvae

47
Q

What consitutes an auto-immune or hyperinfection by Strongyloides Stercoralis?

A
  • Immunocomprimised hosts
  • Accelerated development in small intestines
  • Reinvasion
48
Q

What disease cause Strongyloides Stercoralis in humans?

A
  1. Skin penetration
  2. Larval migration
  3. Intestinal infection
  4. Hyperinfection Syndrome
49
Q

How is Hydatid disease diagnosed?

A
  • History of animal contact
  • CT scan
  • Serology
50
Q

What is the recommended treatment for Hydatid?

A
  • Surgical: removal of accessible cysts

- Albendazole

51
Q

What is the recommended treatment for Strongyloides Stercoralis?

A
  1. Ivermectin

2. Albendazole

52
Q

How is Strongyloides Stercoralis diagnosed?

A
  • Stool or duodenal aspirate for larvae
53
Q

What organism causes Hydatid disease?

A

Echinococcus granulosus (small adult tapeworm)

54
Q

What is the definitive host for Hydatid disease (Echinococcus granulosus)?

A

Dog, jackal, wolf (carnivores)

55
Q

What is the intermediate host for Hydatid disease (Echinococcus granulosus)?

A

Sheep, cattle, horse (herbivores)

56
Q

What is the accidental host for Hydatid disease (Echinococcus granulosus)?

A

Humans

57
Q

Where do Hydatid disease (Echinococcus granulosus) cysts occur in humans?

A

Liver, bone, lungs and brain

58
Q

What defines Hydatid disease?

A

Space occupying lesions in organs, liver and lungs

59
Q

What is the general structure of cestodes (tapeworms)?

A
  • Flattened
  • No digestive tract
  • Scolex with segmented hermaphroditic proglottids (auto-fertilization)
60
Q

What type of life-cycle do cestodes have?

A

Indirect

61
Q

What is the definitive host of cestodes?

A

Humans

62
Q

What is the intermediate host of cestodes?

A

Pigs and cattle

63
Q

How are cestodes of the Taenia solium species transmitted?

A
  • Ingestion of contaminated food with human faeces containing ova
64
Q

What is the pathogenesis of Taenia solium?

A
  • Larvae migrate to muscle and organs (then calcify)

- Neurocysticercosis (seizures and hydrocephaly)

65
Q

How is Taenia solium diagnosed?

A
  • Stool microscopy (need scolex or gravid proglottid to differentiate species)
66
Q

What is the recommended treatment for Taenia solium?

A
  • Albensazole (7-14days)

Microbiology (5 decks)

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