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Immunology > Lecture 22 - Parasites And Infections > Flashcards

Lecture 22 - Parasites And Infections Flashcards

1
Q

What is a general definition of parasite?

A

Any living form which is dependent on other living forms for survival, and causing some damage to the host

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2
Q

What are parasites used to describe?

A 
Protozoa
Helminths (worms)
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3
Q

What are 3 main types of parasites?

A

Protozoa
Helminths
Ectoparasites

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4
Q

What is a Protozoa?

A

Endoparasites (live inside the host body)

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5
Q

What is helminths (worms)?

A

Ascaris
Taenia
Hookworm

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6
Q

What is ectoparasites?

A

Live on the surface of the host
Fleas
Lice
Ticks

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7
Q

What are Protozoa?

A

Not easily defined as very diverse
Distantly related to each other
Belong to kingdom: Protista
All are unicellular eukaryotic organism
Habitats: all aqueous environment (incl soil and us)
Around 20.000 species described (most do not cause disease)

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8
Q

Where are Protozoa diseases common in?

A

Developing countries

Growing emerging threats in developed countries

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9
Q

What can Protozoa be classified by?

A

Their means of locomotion
Pseudopodia (Entamoeba histolytica)
Flagella (Trypanosoma)
Cilia (paramecium)

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10
Q

How does Protozoa reproduce asexually?

A

Binary fission: one cell splits into two

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11
Q

What is schizogony (schizont stage)?

A

Nucleus divides many times before cell divides

The single cell separates into daughter cells

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12
Q

How does some Protozoa reproduce sexually?

A

Fusion of gametes (e.g. plasmodium)

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13
Q

What do some Protozoa produce?

A

Cysts (Giardia, Entamoeba)

Protective capsule to resist unfavourable condition (ie:outside host)

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14
Q

What is Trophozoites?

A

Protozoa in feeding and growing stage

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15
Q

What are 3 forms of Protozoa disease?

A

Apicomplexa (SPOROZOA)
Amoebae
Archaezoa - Euglenozoa (FLAGELLATES)

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16
Q

What are examples of Apicomplexa?

A 
Plasmodium species (malaria)
Toxoplasma Gondi (toxoplasmosis)
Cryptosporidium (diarrhoea)
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17
Q

What is an example of Amoebae?

A

Entamoeba histolytica (amoebic dysentery)

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18
Q

What are some examples of Archaezoa?

A

Giardia (diarrhoea, malabsorption)
Trypanosoma (sleeping sickness, Chagas)
Leishmania (Leishmaniasis)

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19
Q

Where are malaria found?

A

Endemic in parts of Asia, Africa, Latin America and Oceania

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20
Q

How much percentage of the world’s population live in areas where malaria is transmitted?

A

40%

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21
Q

What does WHO estimate?

A

212 million clinical cases per year
429,000 deaths in 2015 (sub-Saharan African - under 5 year old children)
50% reduction since 2000

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22
Q

What is malaria caused by?

A

Apicomplexa protozoan parasites belonging to the genus plasmodium

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23
Q

What are Apicomplexan parasites?

A

Non-motile
Obligate intracellular parasites
Characterised by complex set of organelles at tip of cell

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24
Q

What are 4 plasmodium species that cause malaria?

A

Plasmodium falciparum
Plasmodium vivax
Plasmodium malariae
Plasmodium ovale

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25
Q

What plasmodium species is most common?

A

P. Vivax

80% of malaria infections

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26
Q

What plasmodium species is clinically most important?

A

P.falciparum
15% of malaria infections
90% deaths

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27
Q

What is the transmission of malaria?

A

Causative agent is transmitted in the saliva of pregnant female mosquitoes (Anopheles)
30-40 different Anopheles species transmit the pathogen
Anopheles Gambiae is best known as it transmits most common type of malaria

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28
Q

Sporozoites

A

Found in mosquito saliva gland
Stage transmitted by mosquitos
After injection into the skin, sporozoites move through the dermis until they contact blood vessels
Sporozoites move into the circulatory system
Travel to the liver (30 min after bite)-infect hepatocytes

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29
Q

What does sporozoite develop into?

A

Liver schizont

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30
Q

What is a schizont?

A

Multinucleated parasite (asynchronous division of parasite nucleus)

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31
Q

What does the schizont differentiate to form?

A

Many mononucleared merozoites

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32
Q

Merozoites

A

Liver cell ruptures
Merozoites released into the bloodstream
Infect red blood cells (RBC)

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33
Q

What does merozoites differentiate into?

A

Trophozoite stage

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34
Q

What are young trophozoites called and why?

A

Ring stage

Because of Giemsa staining pattern

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35
Q

Asexual cycle of malaria: RBC

A

The merozoite changes forming a large mononucleated trophozoite
The trophozoite nucleus divides forming a schizont
The schizont differentiates to generate many uninucleated merozoites
RBC ruptures releasing merozoites into the blood
The merozoite invade new RBC - start new asexual cycle

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36
Q

What does some merozoite upon invading RBC develop into?

A

Gametocytes

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37
Q

What are RBC containing gametocytes taken up by?

A

Mosquito

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38
Q

Where does the RBC break down?

A

Insect gut

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39
Q

What does gametocytes form?

A

Male and female gametes

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40
Q

What does the gametes fuse to form?

A

Zygote

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41
Q

What does zygote undergo?

A

Meiosis in the insect guy wall forming an oocyst

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42
Q

What occurs in the oocyst?

A

Repeated mitotic division

Producing thousands of sporozoites

43
Q

When the oocyst ruptures what does it release?

A

Sporozoites into the haemolymph

44
Q

Where does the sporozoite migrate?

A

From gut lining to the salivary gland, starting the life cycle again

45
Q

What is mosquito?

A

Primary or definitive host

Host where parasite reaches maturity and sexually reproduces

46
Q

What are mammals?

A

Intermediate host

Used to get from insect to insect

47
Q

What are the pathology and clinical manifestation of malaria due to?

A

Asexual red blood cell stage

48
Q

What does the symptoms of malaria depend on?

A

Cycle of parasite
Immune state
General health
Nutritional status

49
Q

What are other symptoms of malaria?

A 
High fever
Periodic fever every 48 to 72hr
Chills 
Headaches 
Joint pain 
Vomiting 
Weakeness
Reveal failure 
Confusion 
Seizures
50
Q

What does cerebral malaria result in?

A

Tissue death in the brain (P.falciparium)

51
Q

What is malaria diagnosis?

A

Microscopic detection of parasite in blood smear
Thick blood film - detection
Thin blood film - species identification

52
Q

What are the treatment of malaria?

A

Various antimalarial medications
(Chloroquine, quinine, artemisin)
Type depends on severity of case

53
Q

What are the prevention of malaria?

A 
Reduce:
Human-mosquito context 
Vector density
Parasite reservoir 
Avoid getting bitten 
Use anti-malaria medication (chemoprophulaxis) - chloroquine, mefloquine, primaquine
Insecticide spray
Bed nest with insecticide
54
Q

How many Leishmania species are there?

A

More than 20

55
Q

What are examples of Leishmania?

A

L. Donovani

L. Major

56
Q

Where are Leishmaniasis?

A

Present throughout tropics and subtropics

South-central America, Asia, Africa

57
Q

How many are infected with Leishmaniasis?

A

Around 12 millions
2 millions new case per year
50.000 death per year

58
Q

What is the vector for Leishmania?

A

sand fly

Female: Phlebotomus, Lutzomyia

59
Q

What is the pathology of Leishmaniasis?

A

Begnin skin lesions to fatal systemic disease

60
Q

What are 3 main diseases of Leishmaniasis?

A

Cutaneous
Mucocutaneous
Visceral

61
Q

What is cutaneous?

A

Form presents with skin ulcers

Self-limiting infection

62
Q

What is mucocutaneous?

A

Form presents with ulcers of the skin, mouth and nose

63
Q

What is visceral?

A

Form starts with skin ulcers

Later presents with fever, low red blood cells, large spleen and liver

64
Q

What are the two main parasites form of Leishmaniasis?

A

Promastigote

Amastigote

65
Q

What is Promastigote?

A 
Flagellar stage 
Occurs in sand fly 
Spindle shape 
Non-infectious: insect gut, divide by binary fission at 27
Infectious: attach/invade 
Neutrophils/ macrophages 
Non-dividing
66
Q

What is Amastigote?

A 
Aflagellar stage 
Occurs in vertebrate host 
Round shape: non-motile
Infectious: invade macrophages 
Divide by binary fission (+500 per single cell)
67
Q

What is the first stage in life cycle of Leishmaniasis?

A

Sand fly takes a blood meal in infected host

Ingests macrophages infected with Amastigote

68
Q

What is the 2nd stage of Leishmaniasis?

A

Macrophage ruptures releasing amastigotes in insect gut

69
Q

What is the 3rd stage in life cycle of Leishmaniasis?

A

In midgut amastigotes transform into non-infectious promastigotes

70
Q

What is 5-6th stage in life cycle of a Leishmaniasis?

A

Promastigotes multiply and move to anterior midgut and attach to gut epithelium - prevent elimination

71
Q

What is the 7th stage of Leishmaniasis?

A

Some promastigotes form infective metacyclic promastigotes that detach from gut wall

72
Q

What is the 8-9th stage in life cycle of Leishmaniasis?

A

Infected sand fly takes a blood meal

Metacyclic promastigotes regurgitated into victims bloodstream

73
Q

What is 10-13th stage in life cycle with Leishmaniasis?

A

Promastigote transformed into amastigotes in macrophages

74
Q

What is 14th stage in life cycle of Leishmaniasis?

A

Amastigotes multiply in parasitophorous vacuole

75
Q

What is 15th stage in life cycle of Leishmaniasis?

A

Vacuole and macrophage lyse and release Amastigote and can be taken up by other macrophages

76
Q

What does Leishmania recruit and prevent?

A

Recruit complement
Prevent lytic action
Use complement for phagocytosis

77
Q

What does Leishmaniasis produce?

A

Surface molecule lipophosphoglycan (LPG)

78
Q

Once phagocytosed via complement receptor, what are parasite able to resist?

A

Acidification
Action of hydrolytic enzymes
Reactive oxygen species in phagolysosome

79
Q

What is the pathology of cutaneous (Leishmaniasis)?

A

Most common (10 million case)
Starts as raised painless red lesion at site of sand fly bite
Ulcer wet or dry - no pus formation
Ulcer self heal or diffuse lesion develop

80
Q

What is pathology of Mucocutaneous?

A

Metastasises mucocutaneous lesions
(Mouth/nose/soft plate or anus/genitals)
Can appear week to years after infection
Tissue destroyed - can lead to disfigurement

81
Q

What is pathology of visceral?

A

Most serious form
High fatality rate - 30.000 death per year
Generalised infection of reticuloendothelial system
Liver, spleen, bone marrow, lymph node:
Protuberant abdomen classical sign
Disease progresss to malaise, weakness, wasting syndrome, death

82
Q

What is diagnosis of Leishmaniasis?

A

Detection of parasites in clinical specimen
Detecting amastigotes or culturing promastigotes form aspirates or biopsies from lesions
Serology or intradermal skin tests also used:
Detect anti-Leishmania antibodies ( I.e. K39 Amastigote Antigen)

83
Q

What is the treatment of Leishmaniasis?

A

Pentavalent antinomials
Pentamidine
Amphotericin B

84
Q

What is Pentavelent antimonials?

A

First line treatment
60 year old drug still, effective - mode of action unclear - inhibit enzymes
Administration: parenteral and long duration treatment
Toxic side effects
Increase in drug resistance in Leishmaniasis

85
Q

What is Pentamidine?

A

Interacts with DNA

Inhibits DNA topoisomerase II

86
Q

What is Amphotericin B?

A 
Alternative to antimonials 
Damage parasite membrane 
Administration similar to antimonial
Toxicity reduced 
Treatment expensive
87
Q

What is the control of Leishmaniasis?

A 
Reduced exposure to sand fly 
Use of protective clothing 
Insects repellents 
Bed nets 
Insecticide spray
88
Q

What is the control of reservoir species of Leishmaniasis?

A

Dogs

Vaccine development

89
Q

What is Giardiasis caused by?

A

Giardia duedonalis (lamblia)

90
Q

What is Giardia duedonalis?

A

Anaerobic
Flagellated
Eukaryotic protozoan

91
Q

What is gastrointestinal infection?

A

Abdominal cramp
Vomiting
Explosive
Watery diarrhoea

92
Q

What is transmission of Giardiasis?

A

Faecal/oral (also anthroponotic + zoonotic) could I’m intestinal tracts of animals and in the environment

93
Q

What does Giardiasis?

A

Ingests cysts in contaminated water or swimming

Parasite multiply in the gut

94
Q

What is prevention of Giardiasis?

A

Filtered water

95
Q

What is self-limiting infection of Giardiasis?

A

Asymptomatic to diarrhoea

96
Q

What is worldwide distribution of Giardiasis?

A 
High incidence (20-30%) in developing countries 
Developed countries: travellers and institutionalised population
97
Q

How many people infected with Giardiasis?

A

200 million people infected

98
Q

Where does Giardia mature and multiply?

A

Gut

99
Q

Where is infective cysts passed in?

A

Stool

100
Q

What is the pathogenesis of Giardiasis?

A

Trophozoites multiply in the jejunum by binary fission
Adhere strongly to intestinal epithelium via sucking disks
Diarrhoea May be due to direct cytotoxicity, apoptosis, disruption of epithelial permeability
Giardia cysts excreted in faeces and able to survive in environment until new host infection

101
Q

What is Giardiasis infection characterised by?

A 
Diarrhoea 
Anorexia 
Abdominal pain 
Cramps 
Weight loss 
Offensive fatty stools
102
Q

What is diagnosis for Giardiasis?

A

Microscopic obervation:
Detection of cysts in stools
Aspiration of intestinal content observed for presence of motile trophozoites

103
Q

What is treatment of Giardiasis?

A

Metrodinazole main drug

Active against Giardia trophozoites

Immunology (20 decks)

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