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M&I: Pathogens & Pathogenesis > Parasitology > Flashcards

Parasitology Flashcards

1
Q

What is a parasite?

A

Organism that lives on or in a host organism and gets its food from or at the expense of its host

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2
Q

Name the 3 main classes of parasites

A
  • Protozoa
  • Helminths
  • Ectoparasites
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3
Q

What is a Protozoa?

A

Microscopic single celled organism that can be free living or parasitic

  • are able to multiply in humans and cause disease
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4
Q

Are Protozoa able to multiply in humans?

A

Yes

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5
Q

How can protozoa transmit and where may they live in the body?

A
  • Intestine (transmitted by fecal-oral route)
  • blood or tissue (will usually need a vector)
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6
Q

How do we characterise protozoa?

A

By their mode of movement

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7
Q

Name 4 different classifications of protozoa

A
  • Amoeba
  • Flagellates
  • Ciliates
  • Sporozoa - organisms whose adult stage is not motile
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8
Q

Describe the different shapes and structures/features of protozoa

A

Some may have flagella

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9
Q

What are some examples of the medically important Protozoa infections?

A
  • Entamoeba histolytica
  • Gordia lambton
  • Trichomonas vaginalis
  • Malarias
  • Toxoplasma gondii
  • Cryptosporidium
  • Leishmania species
  • Trypanosoma Cruzi
  • Trypanosoma brucei
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10
Q

What does entamoeba histolyca cause?

A

Ulcers in the duodenum, dysentery

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11
Q

What does gordia lambton cause?

A

Diarrhoea

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12
Q

What does trichomonas vaginalis cause?

A

Infections in the genital tract

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13
Q

What is toxoplasma gondii transmitted through?

A

Cats

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14
Q

What does cryptosporidium cause?

A

Diarrhoea

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15
Q

What does leishmania cause?

A

Ulcers in skin and systemic disease

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16
Q

Describe what Helminths are

A

Helminths are large, multicellular organisms that are usually visible to the naked eye

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17
Q

Can helminths multiply in humans?

A

in their adult form they can NOT multiply in humans so the amount in the body are dependant on the amount of eggs

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18
Q

Name the 3 main groups of helminths

A
  • Nematodes (roundworms)
  • Trematodes (flukes)
  • Cestodes (tapeworms)
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19
Q

Name some medically important N helminths

A
  • Soil - Transmitted helminths
    • Ascaris lumbricoides
    • Trichuris trichiura
    • Hookworm spp.
    • Enterobius vermicularis
  • Filarial parasites
    • Wuchereria bancrofti
    • Loa loa
    • Onchocerca volvulus
    • Dracunculus medinensis
  • Others
    • Toxocara canis/cati
    • Trichinella spiralis
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20
Q

What are the types of nematodes?

A

Soil transmitted helminths
Filarial parasites

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21
Q

Name some medically important T helminths

A
  • Trematodes
  • Schistosoma mansoni/haematobium/japonicum
  • Clonorchis sinensis
  • Fasciola hepatica
  • Paragonimus spp.
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22
Q

What type of worms are nematodes?

A

Roundworms

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23
Q

What does clonorchis sinensis cause?

A

Carcinoma of the bladder

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24
Q

Where does fasciola hepatica live?

A

In the liver

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25
Q

What is special about the male/ female trematodes?

A

Males are larger and the females live inside them

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26
Q

Name some medically important C helminths

A
  • Cestodes
  • Taenia saginata
  • Taenia solium
  • Echinococcus granulosus
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27
Q

What type of worm are trematodes?

A

Flukes

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28
Q

Where does paragonimus live?

A

In the lungs

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29
Q

How long are cestodes?

A

2-3 metres long

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30
Q

What type of worm are cestodes?

A

Tapeworms

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31
Q

Describe what ectoparasites are

A

Blood sucking arthropods such as ticks, fleas, lice and mites that attach or burrow into the skin and remain there relatively long amounts of time (weeks to months)

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32
Q

Name 4 groups of ectoparasites

A
  • Mites
  • Ticks
  • Lice
  • Fleas
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33
Q

Name the medically important mites?

A
  • Scabies
  • Trombiculid
34
Q

Where are scabies found?

A

Animal infected sand

35
Q

Where are trombiculid found?

A

Found in vegetation

36
Q

What are the types of ticks?

A

Hard and soft

37
Q

Name some medically important lice?

A
  • Pediculus humans capitals
  • Pediculus humanus
  • Pthirus pubis
38
Q

What are the types of parasitic host?

A
  • Intermediate

or

  • Definitive
39
Q

What is an intermediate host?

A

Host in which larval or asexual stages develop

40
Q

What is a definitive host?

A

Host in which adult or sexual stage occurs

41
Q

Which factor is correlated strongly to the distribution of parasite infections in humans around the world?

A

Wealth

42
Q

Describe some general different modes of transmission of parasitic infections

A
  • Faeco-oral
  • Food
  • Complex life cycles
  • Others
43
Q

What are DALYs?

A
  • This is one way of measuring morbidity in NTDs (neglected tropical diseases) around the world
  • Disability-adjusted life years - One DALY represents the loss of the equivalent of one year of full health
44
Q

What is Chagas disease and how can we limit it?

A
  • Is Tyrpansoma Cruzi transmitted by bugs that live in thatched rooves and around rubbish, can feed off of animals such as chickens and goats and replicate
  • Can be limited by removing thatched roof, move animals away, keep rubbish away etc.
45
Q

Describe the life cycle of Tyrpansoma Cruzi

A
  • The bug will bite you and then may excrete into the skin
  • Tthe bite will be itchy and so if you itch it then you may cause the parasite in the feces to go into your blood - is not transmitted by the bite
  • Ttryptomastigotes will move to the midgut and replicate then if another bug bites you it can infect that bug
46
Q

Describe the acute phase of Chagas disease

A
  • Incubation 1-2 wks after bite
  • Up to months after transfusion
  • Trypanosomes in blood
47
Q

Describe chronic ‘indeterminate’ (in terms of Chagas disease)

A
  • Chronic ‘indeterminate’
  • Lifelong Infection
  • Generally trypanosomes not detectable but often positive for parasite DNA
  • Seropositive
  • 60-70%
  • Normal ECG and X ravs
48
Q

Describe chronic ‘determinate’ (in terms of Chagas disease)

A
  • Determinate’ Chronic disease
  • Seropositive
  • 30-40% of infected 10-30 years after infection
  • 5-10% develop chronic Chagas immediately after acute disease
49
Q

Describe the symptoms of acute Chagas disease

A
  • Occurs within 3 weeks
  • Generally mild or asymptomatic
    • Local swelling (Romaña)
    • Nodule or chagoma
    • Fever
    • Anorexia
    • Lymphadenopathy
  • 1-2% diagnosed
  • Symptoms last 8-10 wks
  • Rarely (young and IS)
    • Hepatopsplenomegaly
    • Acute myocarditis
    • Meningoencephalitis
    • Fatality <5% of symptomatic
50
Q

Describe the chronic changes of Chagas disease to the heart

A

enlarged heart and thin heart wall → heart failure

51
Q

Describe the effects of Chagas disease on the digestive system

A
  • Severe constipation causes megacolon and ulceration, performation
  • Can affect the esophagus, rectum and sigmoid colon
52
Q

Explain how Chagas disease causes these effects (pathogenesis) in acute, intermediate and chronic Chagas

A

Acute

  • Tissue damage by inflammation due to parasite nests of amastigotes in cardiac, skeletal and smooth muscle
  • Parasite killing by antibodies and activated innate immune response - inflammatory cytokines

Chronic inflammatory response to persistent parasites in muscle and nerve cells

  • Autoimmune mechanisms
  • May vary by parasite strain and tissue tropism
  • Predominance of Th1 cytokines and CD8+ T cells
53
Q

What is the vector of Cutaneous Leishmaniasis?

A

Sam flies - they are very small (can go through mosquito nets)

  • love chickens
54
Q

Which cells do the amastigotes of Cutaneous Leishmaniasis infect?

A

Macrophages - they will be packed full of the amastigotes

55
Q

How does Cutaneous Leishmaniasis present?

A

People will have lesions with large ulcers (there is a plaque formed that will break down and leave a large ulcer)

56
Q

What is mucocutaneous Leishmaniasis?

A
57
Q

Describe what causes these acute lesions (so the pathogenesis) in cutaneous leishmaniasis

A
  • Acute lesions
    • Tissue damage caused by inflammatory response to presence of parasites in
      macrophages
    • Parasite killing by Th1 pro-inflammatory responses and macrophage killing.
  • Latency
    • Parasites remain present long-term. Regulatory immune response characterized by
      balance of Th1 and anti-inflammatory responses
  • Relapse (rare)
    • Alteration in immune response (i.e change in Th1 vs. immune regulation secondary
      to HIV, malnutrition) may trigger relapse
      • Mucocutaneous disease associated with strong but inadequate inflammatory response to parasites that have metastasized to mucosa
      • Diffuse cutaneous leishmaniasis associated with uncontrolled parasite replication.
      • Recividans - recurrence of lesions at old ulcer site.
58
Q

Explain what amastigotes are

A
  • An amastigote is a protist cell that does not have visible external flagella or cilia.
  • The term is used mainly to describe an intracellular phase in the life-cycle of trypanosomes that replicates
59
Q

What are some examples of neglected tropical diseases?

A
  • Lymphatic filariasis
  • Onchocerciasis
  • Guinea worm disease
60
Q

What are the types of parasitic vectors?

A
  • Mechanical
  • Biological
61
Q

What is a mechanical vector?

A

No development of parasite in vector

62
Q

What is a biological vector?

A

When some stages of the life cycle occur

63
Q

What is the life cycle of schistosomiasis?

A
  • Eggs expelled in urine or faeces
  • Develop in fresh water
  • Invade snails
  • Asexual reproduction that amplifies parasite number
  • Infect people when they come into contact with the infected water
64
Q

How can you decrease the faeco-oral transmission of parasites?

A
  • Household sanitation
  • Access to clean water
  • Personal hygiene behaviours
65
Q

How can you decrease the food transmission of parasites?

A
  • Animal husbandry
  • Surveillance
  • Regulations and government controls
66
Q

What is chagas infected with?

A

Metacyclic trypomastigotes

67
Q

What do metacyclic trypomastigotes do?

A

Multiply in cells and burst them, spreading disease further

68
Q

What are the phases of chagas?

A
  • Acute
  • Chronic indeterminate
  • Chronic determinate
69
Q

What are the organs most affected in chronic chagas?

A

Heart and intestines

70
Q

Why does chronic chagas affect the heart and intestines?

A

Damages the autonomic nervous system

71
Q

What complications in the mega colon are caused by chronic chagas?

A

Hecatoma
Obstruction
Sigmoid volvulus
Ulceration
Perforation

72
Q

What is the pathogenesis of acute chagas?

A

Tissue damage caused by inflammatory response to parasite

73
Q

What is the pathogenesis of indeterminate chronic chagas?

A

Regulatory immune response characterised by IL-10 and IL-17

74
Q

Where are visceral leishmaniasis found?

A
  • Asia
  • Middle East/ Africa
  • Latin america
75
Q

Where (geographically) are cutaneous leishmaniasis found?

A
  • Mediterranean
  • Central and South America
76
Q

What is the lifecycle of a leishmaniasis?

A

Sandfly bite
Promashyotes enter immune cells and replicate to form amastigotes

77
Q

What is the old world vector of leishmaniasis?

A

Sergentomyia

78
Q

What are the new world vectors of leishmaniasis?

A

Phlebotomus

79
Q

What is the reservoir of leishmaniasis?

A

Domestic dogs and rodents like sloth

80
Q

How do cutaneous leishmaniasis present?

A

Small Papule that grows into a plaque

81
Q

How do you get a sample for cutaneous leishmaniasis?

A

Scrape from the edge of the plaque onto a slide, then stain with giemsa

82
Q

Describe the effects of Chagas disease on the digestive system

A
  • Severe constipation causes megacolon and ulceration, performation
  • Can affect the esophagus, rectum and sigmoid colon

M&I: Pathogens & Pathogenesis (7 decks)

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