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Y2 MCD Microbiology RI > Parasitic Infections > Flashcards

Parasitic Infections Flashcards

1
Q

Define parasite.

A

An organism living in or on a host and dependent on the host for nutrition – causing damage

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2
Q

What is the difference between an endoparasite and an ectoparasite?

A

Endoparasite – exist INSIDE the host

Ectoparasite – exist on the host

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3
Q

What are the two groups of endoparasites and what are the features of organisms within these two groups?

A

Protozoa

Metazoa

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4
Q

State the classes of organisms within the two groups of endoparasites.

A 
Protozoa  
 Amoeba
 Coccidia
 Ciliates
 Flagellates

Metazoa
 Roundworms
 Flatworms
 Flukes

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5
Q

Give some examples of amoeba.

A

Entamoeba histolytica

Entamoeba dispa

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6
Q

Give some examples of coccidia.

A

Plasmodium species
Toxoplasma
Cryptosporidium

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7
Q

Give an example of a ciliate.

A

Balantidium coli

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8
Q

Give some examples of flagellates.

A

Trypanosoma
Trichomonas
Giardia
Leishmania

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9
Q

What is the main difference between the two types of amoeba?

A

Entamoeba histolytica can cause invasive amoebiasis

Entamoeba dispar is a normal commensal of the GI tract

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10
Q

What is amoeba infection caused by?

A

Ingestion of mature cysts in food or water contaminated by faeces

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11
Q

Describe how E. histolytica infection causes disease.

A

The cysts enter the small intestine and release active amoebic particles (trophozoites), which invade the epithelial cells of the large intestines, causing flask-shaped ulcers

Infection can spread from the intestines to other organs

Invasive amoebiasis may often cause amoebic liver abscesses

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12
Q

How many nuclei are there in mature cysts?

A

4

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13
Q

What are the treatment options for amoebiasis?

A

Nitroimidazole derivatives (kills trophozoites but not the cysts)

Parmomycine or Diloxanide Furoate

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14
Q

What are the five types of plasmodium that cause malaria?

A 
Falciparum 
Malariae 
Vivax 
Ovale 
Knowlesi
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15
Q

What are the two types of host for plasmodium?

A

Human

Female anopheles mosquito

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16
Q

What are the two stages of malaria in humans?

A

Liver

Blood

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17
Q

Describe the symptoms of malaria.

A 
PAROXYSMAL (occurs every 4-8 hours) 
Fever  
Chills 
Headaches  
Vomiting  
Muscle pain
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18
Q

State some complications of malaria.

A 
Severe anaemia (due to intravascular haemolysis) 
Cerebral malaria 
Liver failure  
Shock  
Pulmonary oedema 
Abnormally low blood sugar 
Kidney failure  
Swelling and rupturing of the spleen
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19
Q

What are the treatments for uncomplicated malaria?

A

Chloroquine

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20
Q

What is the treatment for severe malaria?

A

Artemisinin-based combination therapy

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21
Q

How is malaria diagnosed?

A

Blood film (+ Giemsa stain)

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22
Q

What are the routes of infection of toxoplasma gondii?

A

Eating undercooked meat of animals harbouring tissue cysts

Consuming food or water contaminated with cat faeces

Blood transfusion

Organ transplantation

Transplacentally from mother to foetus

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23
Q

Which group of patients are particularly vulnerable to toxoplasma infection?

A

Immunocompromised and in pregnancy - the fetus

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24
Q

What can toxoplasma infections cause in immunocomprimised individuals?

A

CNS disease
Brain lesions
Pneumonitis
Retinochoroiditis

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25
Q

What does cryptosporidium cause?

A

DIARRHOEA (mainly in the immunocompromised)

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26
Q

How is it treated?

A

Fluid rehydration

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27
Q

How are most diarrhoeal protozoal diseases diagnosed?

A

Stool examination

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28
Q

What are the reservoirs of balantidium coli?

A

Primates
Rodents
Pigs

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29
Q

What are the effects of balantidium coli infection in immunocompromised patients?

A 
Persistent DIARRHOEA 
Dysentery 
Abdominal pain 
Vomiting  
Nausea

Note:
If left untreated can cause perforation of the colon

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30
Q

How can drinking water be cleared of ovoid giardia lamblia cysts?

A

Filtration

Ovoid cysts can survive standard chlorination procedures

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31
Q

What is the main symptom of giardiasis?

A

DIARRHOEA

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32
Q

How is giardia transmitted?

A

Faeco-oral

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33
Q

What are the acute symptoms of giardiasis?

A 
Diarrhoea 
Greasy stools that tend to float  
Stomach or abdominal cramps  
Nausea/vomiting
Dehydration
34
Q

What is the treatment for giardia?

A

Metronidazole - doesn’t kill cysts only the trophozoites

35
Q

How is trichomonas transmitted?

A

Sexually transmitted

36
Q

Where does trichomonas infection mainly tend to reside?

37
Q

What are the symptoms of trichomoniasis?

A 
Up to 50% aysmptomatic
Dysuria 
Vulval itching  
Vaginal discharge  
Offensive smelling urine
38
Q

What effect does trichomonas infection have on HIV transmission?

A

It enhances HIV transmission

39
Q

What is the treatment for trichomoniasis?

A

Metronidazole

40
Q

Can adult worms multiply in man?

41
Q

In which subset of the population is there a significant burden of worms?

A

School-aged children – this has a massive impact on their development

42
Q

What are the three groups of Helminths(metazoa)? Give some examples of each.

A 
Roundworms (nematodes) 
 Ascaria 
 Hookworms 
 Filaria 
 Strongyloides

Flatworms (cestodes)
 Taenia (tapeworms)

Flukes (trematodes)
 Schistosoma

43
Q

Where do the adult ascaria worms live?

A

Small intestine

44
Q

Describe the passage of ascaria larvae once they hatch in the small intestine.

A

Infective eggs are swallowed

The larvae hatch in the small intestine and invade the intestinal mucosa

They are carried via the portal and systemic circulation to the lungs

The larvae mature further in the lungs, penetrate the alveolar walls, ascend the bronchial tree and are swallowed

When they reach the small intestine, they mature into adult worms

45
Q

How long can adult ascaria live?

46
Q

Describe the symptoms of ascariasis.

A

Often asymptomatic

Infections with a large number of worms can cause abdominal pain or intestinal obstruction

Malnourishment (because of worms feeding on contents of small intestine)

Loeffler’s pneumonia – penetration of larvae into lungs leads to pools of blood and epithelial cells clogging the airspaces in the lungs (resulting bacterial infections can be fatal)

47
Q

What is the treatment for ascariasis?

A

Albendazole or Mebendazole

48
Q

How are most helminth infections diagnosed?

A

Stool examination

49
Q

Describe the passage of hookworm larvae across the body.

A

The same as ascaria

50
Q

Where do adult hookworms live?

A

Small intestine

Attached by their buccal capsules to the villi of the small intestine

51
Q

What is a key feature of hookworm infection and what is this caused by?

A

Iron deficiency anaemia – caused by localised bleeding in the small intestine

52
Q

What is the treatment for hookworm infection?

A

Albendazole or Mebendazole

53
Q

What is the biological name whipworm?

A

Trichuras trichiura

54
Q

Where do adult whipworms live?

A

Caecum and ascending colon

55
Q

What are the symptoms of whipworm infection?

A

Blood diarrhoea and anaemia (due to severe vitamin and iron loss)

Inflammation of intestinal wall

Can develop rectal prolapse

56
Q

What is the treatment for whipworm infections?

A

Albendazole or Mebendazole

57
Q

What is a potential therapeutic use of whipworms?

A

Helminth therapy for allergies and autoimmune diseases

58
Q

What are the two forms of filaria?

A

Brugia malayi

Wucheria bancrofti

59
Q

Describe the location of microfilariae in the blood.

A

They are found in the peripheral blood at night

They are found in the deep veins during the day

60
Q

How is lymphatic filariasis diagnosed?

A

Blood smear

Antigen detection with immunochromatic test (ELISA)

61
Q

What is a distinguishing feature of Loiasis?

A

Female worms can get into the eye and cross under the conjunctiva so you see something wriggling in your vision

62
Q

What is the insect vector in Loiasis?

A

Chyrops fly

63
Q

What are the three main types of flatworm for which humans are the only definite host?

A

Taenia solium
Taenia asiatica
Taenia saginata

64
Q

Describe the symptoms of flatworm infection.

A

Most people are asymptomatic

Abdominal pain
Weight loss
Loss of appetite
Upset stomach

NOTE: people with T. saginata infection tend to have more symptoms

65
Q

How is flatworm infection diagnosed?

A

Stool examination – tapeworm segments are found in the stool or identification of eggs in the stool

66
Q

What important condition does Taenia solium cause?

A

Cysticercosis - commonest acquired cause of epilepsy worldwide

67
Q

What is the treatment for flatworm infections?

A

Praziquantel

68
Q

What are the three main types of schistosoma?

A

Schistosoma mansoni
Schistosoma haematobium
Schistosoma japonicum

69
Q

What is the intermediate host in schistosoma?

A

Freshwater snails

70
Q

Where do the adult worms live in schistosomiasis?

71
Q

Where do the eggs progressively move to?

A 
Small intestine (mansoni and japonicum) 
Bladder and ureters (haematobium)
72
Q

Describe the symptoms of schistosomiasis.

A 
Possible rash or itchy skin  
Fever  
Chills  
Cough  
Muscle aches  
Most people have NO SYMPTOMS in early stages of infection
73
Q

What is the treatment of schistosomiasis?

A

Praziquantel

74
Q

Name some ectoparasites.

A

Sarcoptes scabiei – Scabies (causes rash)
Pediculus humanis capitis (head louse)
Pediculus humanis corporis (body louse)
Pthirus pubis (crab louse)

75
Q

How are ectoparasites transmitted?

A

Direct contact

76
Q

What are the features of protozoa?

A

 Unicellular
 Eukaryotes (membrane bound nucleus)
 Some have insect vectors
 NO eosinophilia

77
Q

What are the features of metazoa?

A

 MULTIcellular
 They are helminths/worms
 Free living, intermediate hosts and vectors
 Cause eosinophilia if they invade the blood
Cycles involve insects vectors and intermediate hosts
For most - few zoonoses

78
Q

What are the reservoirs of E. histolytica?

A

Humans are the only reservoir

79
Q

What are the complications of Trichomoniasis

A

Detrimental outcome on pregnancy and is associated with preterm delivery and low birth weight

80
Q

Define parasite

A

Organism living in or on the host and dependent on it for nutrition - causing damage

81
Q

How do you get infected by a fluke cercaria?

A

Patient has to be in infected water so cercaria can penetrate the skin

82
Q

How are scabies treated?

A

Scabicides

Y2 MCD Microbiology RI (8 decks)

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