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Microbiology > 5- Parasitology > Flashcards

5- Parasitology Flashcards

1
Q

What is the definition of a parasite?

A

A parasite is an 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

What are the three classes of parasites that can cause disease in humans?

A

➝ Protozoa
➝ Helminths
➝ Ectoparasites

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3
Q

What are protozoa?

A

➝ single celled, microscopic organisms that can be free-living of parasitic in nature
➝ able to multiply in humans allowing serious infections to develop from a single organism.

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4
Q

How can intestinal protozoa be transmitted?

A

➝ fecal-oral route

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5
Q

How can blood or tissue protozoa be transmitted?

A

➝ Arthropod vector

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6
Q

How are protozoa classified?

A

➝ The mode of movement

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7
Q

What are the 4 types of protozoa?

A

➝ Amoeba
➝ Flagellates
➝ Ciliates
➝ Sporozoa

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8
Q

What is an example of an amoeba?

A

➝ Entamoeba

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9
Q

What are two examples of a flagellate?

A

➝ Giardia

➝ Leishmania

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10
Q

What is an example of a ciliate?

A

➝ balantidium

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11
Q

What is a sporozoa and give 2 examples?

A

➝ Organisms whose adult stage is not motile

➝ plasmodium and cryptosporidium

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12
Q

List 9 medically important protozoa infections

A 
Entamoeba histolytica
Giardia lamblia
Trichomonas vaginalis
Malaria (Plasmodium spp.)
Toxoplasma gondii
Cryptosporidium
Leishmania spp.
Trypansoma cruzi
Trypansoma brucei (gambiense/rhodesiense)
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13
Q

What does entamoeba histolytica cause?

A

➝ amoebic dysentery which presents with loss of epithelium

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14
Q

What does giardia lamblia cause?

A

➝ Diarrhoea

➝ Epithelial damage and blunting of microvilli

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15
Q

What does trichomonas vaginalis cause?

A

➝ Vaginal discharge

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16
Q

How is toxoplasma gondii transmitted?

A

➝ through cat faeces

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17
Q

What can cryptosporidium cause?

A

➝ Epidemic diarrhoea

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18
Q

What type of infection is cryptosporidium and who does it affect?

A

➝ Opportunistic infection that arises in immunosuppressed people

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19
Q

What type of an infection is leishmania?

A

➝ Protozoal

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20
Q

What does leishmania cause?

A

➝ severe systemic illness and cutaneous disease

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21
Q

What disease does trypanosoma cruzi cause and where is it endemic to?

A

➝ Chagas disease

➝ South America

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22
Q

What disease does trypanosoma brucei cause?

A

➝ African sleeping sickness

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23
Q

What are helminths?

A

➝ Large multicellular organisms (worms) generally visible to the naked eye in their adult stages
➝ in their adult form cannot multiply in humans

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24
Q

What are the three main groups of helminths that are human parasites?

A

➝ Nematodes (roundworms)
➝ Trematodes (flukes)
➝ Cestodes (tapeworms)

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25
Q

What are the two important types of nematodes?

A

➝ Soil transmitted helminths

➝ Filarial parasites

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26
Q

What are 4 examples of soil transmitted helminths?

A

➝ Ascaris lumbricoides
➝ Trichuris trichuria
➝ hookworm
➝ enterobius vermicularis

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27
Q

What are 4 examples of filarial parasites (helminths)?

A

➝ Wuchereria bancrofti
➝ Loa loa
➝ Onchocerca volvulus
➝Dracunculus medinesis

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28
Q

What does Wuchereria bancrofti cause?

A

➝ Elephantiasis

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29
Q

What are two other important helminths other than the filarial parasites and soil transmitted helminths?

A

➝ Toxocara canis/cati

➝ trichinella spiralis

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30
Q

Give 4 examples of medically important trematodes?

A

➝ Schistosoma mansoni/haematobium/japonicum
➝ Clornochis sinensis
➝ Fasciola hepatica
➝ Paragonimus

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31
Q

What does paragonimus cause?

A

➝ TB like illness

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32
Q

What does clornochis sinensis cause?

A

➝ Cholangiocarcinoma

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33
Q

Give 3 examples of medically important cestodes?

A

➝ Taenia saginata
➝ Taenia solium
➝ Echinococcus granulosus

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34
Q

What can taenia solium cause?

A

➝ cysts in the brain

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35
Q

What can echinococcus granulosus cause?

A

➝ hydatid disease

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36
Q

What are ectoparasites?

A

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

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37
Q

What are 2 examples of mites?

A

➝ Scabies

➝ Trombiculid

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38
Q

What are two types of ticks?

A

➝ hard

➝ soft

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39
Q

What are three types of lice?

A

➝ Pediculus humanus capitis
➝ Pediculus humanus humanus
➝ Pthirus pubis

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40
Q

What are the two types of parasitic host?

A

➝ Intermediate

➝ Definitive

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41
Q

What is an intermediate host?

A

➝ a host in which larvae or asexual stages develop

42
Q

What is a definitive host?

A

➝ a host in which the adult or sexual stage occurs

43
Q

What are the two types of parasitic vectors?

A

➝ Mechanical

➝ Biological

44
Q

What is a mechanical vector?

A

➝ When there is no development of the parasite in the vector

45
Q

What is a biological vector?

A

➝ When some stages of the life cycle of the parasite occur in the vector

46
Q

Describe the life cycle of schistosomiasis?

A

➝ eggs passed in urine, hatch, releasing miracidia in water
➝ miracidia enter snails and multiply
➝snail becomes an amplifier and there is asexual reproduction in the cell
➝cercariae emerge from snails
➝ wash clothes in contaminated water
➝ cercariae penetrate unbroken skin or mucous membranes by means of enzymatic secretions
➝ the cercariae infect the humans
➝ they develop into adults in the host
➝ the adults undergo sexual reproduction and the female releases eggs
➝released into environment by urination

47
Q

Where are most parasitic infections from?

A

➝ Animals

limited opportunities for transmission to humans

48
Q

What is DALY?

A

➝ Disease adjusted life years

49
Q

Why is DALY a unit of measurement?

A

➝ Many infections are not fatal but they cause chronic illness
➝ DALY measures the amount of disability years

50
Q

How can feco-oral route using parasites be eradicated without medication?

A

➝ Household sanitation
➝ Access to clean water
➝ personal hygiene behaviors

51
Q

How can food route using parasites be eradicated without medication?

A

➝ Animal husbandry
➝ Surveillance
➝ Government control and regulation

52
Q

How can we help eradicate parasites with complex life cycles?

A

➝ Monitor the distribution of infection in vectors and intermediate/ definitive hosts

53
Q

What are other ways of eradicating parasitical infections?

A

➝Government resources and level of human development/per capita income
➝Education
➝Country-level and regional control programmes
➝Availability of cheap and efficacious treatments
➝Construction and building regulations (eg Chagas)
➝Urban vs. rural residence
➝Environmental sanitation

54
Q

Describe how Chagas disease occurs?

A

➝ Reduviidae bugs feed on the human and defecate
➝ when the bite is scratched you can scratch the faeces into your skin
➝ the parasite enters and multiplies in nerve or muscle cells
➝ the cells rupture releasing thousands of trypomastigotes that can be taken up by the bug again

55
Q

Where is Chagas disease endemic to?

A

➝ Latin and south America

56
Q

What parasite is Chagas disease caused by?

A

➝ Trypanosoma Cruzi

57
Q

What are the three phases of Chagas disease?

A

➝ Acute
➝ Chronic ‘indeterminate’
➝ Chronic ‘determinate’

58
Q

What are the three characteristics of the acute phase of Chagas disease?

A

➝ incubation 1-2 weeks after bite
➝ up to months after transfusion
➝ trypanosomes in blood

59
Q

What are the 5 characteristics of the chronic ‘indeterminate’ phase of Chagas disease?

A 
➝ Lifelong infection
➝ Generally trypanosomes NOT detectable but often positive for parasite DNA
➝ seropositive
➝ 60-70% of infected
➝ normal ECG and X-rays
60
Q

What are the 3 characteristics of the ‘determinate’ chronic phase of Chagas disease?

A

➝ seropositive
➝ 30-40% infected
➝ 10-30 years after infection

61
Q

What % of people develop chronic Chagas after the acute disease?

A

➝ 5-10%

62
Q

What are the symptoms of acute Chagas disease?

A 
➝ Generally mild or asymptomatic
➝ Local swelling (Romaña)
➝ nodule or chagoma
➝ fever
➝ anorexia
➝ lymphadenopathy
63
Q

When do the symptoms of acute Chagas disease occur within and how long do they last?

A

➝ 3 weeks

➝ symptoms last 8-10 weeks

64
Q

What are the rare complications of acute Chagas disease?

A 
➝ occur in the young and immunosuppressed 
➝ Hepatosplenomegaly
➝ Acute myocarditis
➝ Meningoencephalitis
➝ Fatality <5% of symptomatic
65
Q

What are the cardiac effects of chronic Chagas disease?

A

➝ There is damage to the conduction system of the heart
➝ this causes arrhythmia
➝ sudden ventricular fibrillation
➝ damage to the heart muscle wall, thin and enlarged causing cardiomyopathy, heart failure
➝ mitral regurgitation
➝ apical aneurysms can occur
➝ sudden death due to arrhythmia is common

66
Q

What % of people with chronic Chagas disease are affected with digestive issues?

A

➝ 10-15%

67
Q

What digestive organs are most affected in chronic Chagas?

A

➝ Esophagus
➝ rectum
➝ sigmoid colon

68
Q

What are the complications of a megacolon during Chagas disease?

A 
➝ Faecaloma
➝ Obstruction
➝ Sigmoid volvulus
➝ Ulceration
➝ Perforation
69
Q

What is the presentation of a megacolon?

A

➝ constipation

70
Q

Describe the progression from acute Chagas to chronic?

A

➝ Acute illness occurs that is not symptomatic
➝ Parasites appear in the blood
➝ the immune response starts to control the parasite numbers and you go into the indeterminate phase
➝ after many years there is development of chronic Chagas disease

71
Q

Describe the natural course of Trypanosomiasis

A

➝ incubation period 5-10days
➝10 days- 8 weeks= patent parasitaemia, acute Chagas disease, mild illness
➝ after 8 weeks- immune response effective in controlling parasite numbers, intermediate phase
➝ 5-40 years, Chronic Chaggas disease, subpatent parasitaemia, morbidity, mortality

72
Q

What is tissue damage in acute Chagas caused by?

A

➝ Tissue damage caused by the inflammatory response to parasite in nests of amastigotes in cardiac, skeletal and smooth muscle

73
Q

How does parasite killing occur in acute Chagas?

A

➝ Parasite killing by antibodies
➝ activated innate immune response
➝ Th1 inflammatory cytokines

74
Q

What is the immune response to Chagas in the indeterminate phase characterised by?

A

➝ Regulatory immune response characterized by IL-10 and IL-17

75
Q

What is the type of immune response to Chagas in the chronic phase?

A

➝ 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

76
Q

What are the cytokine profiles in mild vs severe Chagas disease?

A

➝ in mild more IL17 and IL10 produced

➝ in severe more inflammatory cytokines like TNF alpha and interferon gamma produced

77
Q

What are the two main types of leishmaniasis?

A

➝ Visceral and Cutaneous

78
Q

What are the three geographical regions affected by visceral leishmaniasis?

A

➝ Asia
➝ Middle east/Africa/Asia
➝ Latin america

79
Q

What type of visceral leishmaniasis affects Asia?

A

➝ Leishmania donovani

80
Q

What type of visceral leishmaniasis affects the Middle east & Africa?

A

➝ L.Infantum variants

81
Q

What type of visceral leishmaniasis affects Latin America?

A

➝ L. Chagasi

82
Q

What type of cutaneous leishmaniasis affects the old world?

A

➝ Mediterranean/Middle East

➝ L. Infantum/L. major/L. tropica

83
Q

What types of cutaneous leishmaniasis affect the new world?

A

➝ Central and South America

➝ L.braziliensis/amazonensis/mexicana

84
Q

What is Leishmaniasis caused by?

A

➝ infection with Leishmania parasites, which are spread by the bite of phlebotomine sand flies

85
Q

Describe the lifecycle of leishmaniasis?

A

➝ The sand-fly bites and transmits a promastigote
➝ The promastigote invades immune cells eg. macrophages
➝ Inside the macrophage it forms nests of amastigotes, which multiply asexually to form more
➝ the cells eventually burst which release lots of amastigotes and infect other cells which can be taken up by the fly

86
Q

What is the vector of leishmaniasis?

A

➝ Lutzomyia/phlebotomus

87
Q

In what regions are sandflies common and who do they affect?

A

➝ Tropical regions
➝ people who live in housing of poor standard such as adobe
➝ sandfly lives in cracks of these houses

88
Q

What type of an infection is leishmaniasis?

A

➝ Zoonotic

89
Q

What is the sylvatic and domestic reservoir of leishmaniasis?

A

➝ sylvatic ➝ rodents

➝ domestic ➝ dogs

90
Q

Describe the progression of cutaneous leishmaniasis after a bite?

A

➝ There is a papule that forms and spreads

➝ the centre becomes necrotic and ulcers form

91
Q

What happens if you get infected as a child with cutaneous leishmaniasis?

A

➝ early immunity to that form of leishmania

92
Q

When does diffuse cutaneous leishmaniasis occur?

A

➝ When there is lack of an immune response to the leishmania

93
Q

Describe the progression of mucocutaneous leishmaniasis?

A

➝ infected as child
➝ years later a small proportion of individuals get congested noses
➝ lesions occur in the mucus membranes
➝ lesions occur and destroy the nasal septum

94
Q

When do people get infected with mucocutaneous leishmaniasis?

A

➝ as children

95
Q

What are the three phases of cutaneous leishmaniasis?

A

➝ Acute lesions
➝ Latency
➝ Relapse (rare)

96
Q

Describe the pathogenesis of acute lesions in cutaneous leishmaniasis?

A

➝ Tissue damage is caused by inflammatory response to the presence of parasites in macrophages
➝ parasite killing by Th1 proinflammatory responses and macrophage killing

97
Q

Describe the pathogenesis of the latency phase in cutaneous leishmaniasis?

A

➝ regulatory immune response characterised by balance of Th1 and anti-inflammatory responses
➝ parasites remain present long term

98
Q

What is a Recividans?

A

➝ A recurrence of lesions at the old ulcer site

99
Q

What is mucocutaneous disease associated with?

A

➝ strong but inadequate inflammatory response to parasites that have metastasised to mucosa

100
Q

What can trigger relapse in leishmaniasis?

A

➝ alteration in immune response

i.e. change in Th1 vs. immune regulation secondary to HIV, malnutrition

101
Q

What is diffuse cutaneous leishmaniasis associated with?

A

➝ uncontrolled parasite replication

Microbiology (11 decks)

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