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FDN3 By Nathan and Minnie > Parasites > Flashcards

Flashcards in Parasites Deck (128)
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1

What is the difference between an intermediate host and a definitive host of a parasite?

Intermediate = harbors the larval (asexual) stage of the parasite

Definitive = harbors the adult (sexual) stage of the parasite

 

2

Based on this image, which organism is the definitive host of malaria?

Which is the intermediate?

Why?

Mosquitos are the definitive hosts

Humans are the intermediate hosts

Adult sexual stage occurs in mosquitos

3

What is a paratenic host of a parasite?

A host that harbors a form of the parasite that does not undergo further development

4

Cestodes are _____worms

Tapeworms

(a type of flat worm)

5

Trematodes are _____worms

Flatworms/flukes

6

Nematodes are _______worms

Roundworms

7

A parasitic infection that causes eosinophilia is most likely a..

A) Protozoa

B) Helminth

Helminth

(Helminth infetions are associated with eosinophilia, protozoa infections are not)

8

What are the three main groups of protozoa?

Amoebae

Flagellates

Sporozoans

9

In which protozoal group is trypanosoma in?

What disease is it associated with?

Flagellates (Hemoflagellates)

Chaga's disease (cruzi) and African Sleeping Sickness (brucei)

10

Leishmania is in which protozoal group?

Which disease is it associated with?

Flagellates (hemoflagellate)

Leishmaniasis

11

Which insect carries the parasite that causes Chagas' disease?

Which parasite?

Reduviid (Triatomine, "kissing bug")

Trypanosoma cruzi, a hemoflagellate

12

What are the clinical manifestations of Trypanosoma cruzi infection?

Chagas' Disease

  • Acute phase (high parasitemia)
    • Periorbital edema (Romana's sign)
    • Fever
    • Anorexia
    • Hepatomegaly
    • Lymphadenopathy
    • Death (occasionally, mostly in infants)
  • Chronic phase (undetectable parasitemia)
    • Cardiomyopathy
    • Megaesophagus
    • Megacolon
    • (everything is swollen)

 

13

Which of the following is a human pathogen?

A. Iodamoeba butschlii

B. Entamoeba coli

C .Entamoeba dispar

D. Entamoeba histolytica

E. Dientamoeba fragilis

D. Entamoeba histolytica

14

List the intestinal protozoa relevant to FDN3

  • Amoebae = Entamoeba histolytica
  • Flagellates = Giardia lamblia
  • Sporozoans = Cryptosporidium spp. 

 

 

15

List the blood and tissue protozoa relevant to FDN3

  • Amoebae
    • Naegleria spp
  • Flagellates
    • Trypanosoma spp (cruzi and bruci)
    • Leishmania spp
    • Trichomonas vaginalis
  • Sporozoans
    • Plsamodium spp
    • Toxoplasma gondii

 

16

Which insect carries the parasite that causes African Sleeping Sickness?

Which parasite?

Tsetse fly

Trypanosoma brucei

17

Think about the two relevant Trypanosoma species:

What are they?

Which insect carries each one?

Which diseases do they cause?

  • Trypanosoma cruzi
    • Reduviid bug (Triatomine, "Kissing bug")
    • Causes Chagas' disease
       
  • Trypanosoma brucei
    • Tsetse fly
    • Causes African Sleeping Sickness

18

What is the clinical presentation of Trypanosoma brucei infection?

African Sleeping Sickness

Bite: non-pustular, painful, itchy chancre 1-3 weeks after bite

  • East African = Acute
    • T. brucei rhodensiense
    • Abrupt onset of fever
    • Headache 
    • Occipital lymphadenopathy (Winterbottom's sign)
  • West African 
    • T. brucei gambiense 
    • Subacute, chronic meningoencephalitis
    • Subtle personality changes
    • Somnolence
    • Coma
    • Death

 

19

How is African Sleeping Sickness diagnosed?

See trypomastigotes of Trypanosoma in blood smear or CSF

20

This sample from the patient's blood shows a parasite, identified as a flagellated protozoa 

Could this be Leishmania? Why or why not?

This could not be leishmania

Leishmania spp. in humans do not swim around in the blood, as this protozoa is doing; they only infect macrophages in their amastigote form 

(amastigote = a-mobile = immobile)

The species shown above is Trypanosoma, in its trypomastigote form

21

How is Chagas' disease diagnosed?

Serology

22

How does Trypanosoma brucei evade the host immune system?

Trypanosoma brucei = African Sleeping Sickness

Variant surface glycoproteins (VSGs) sheild the parasite and prevent the host immune system from accessing the plasma membrane or any other stable epitopes 

If an antibody binds a VSG, the VSG is absorbed and recycled

23

Which insect carries the parasite that causes Leishmaniasis?

Which parasite?

The sandfly (phlebotamine)

Carries Leishmania spp

Note: Different species are associated with different regions and flavors of disease

24

Which protozoa can be sexually transmitted?

Trichomonas vaginalis

 

25

Which stage of the protozoal flagellate life cycle is most likely to be found in the tissues and macrophages of humans?

Amastigote

This is the form that is NOT mobile, found in tissues and macrophages
(Leishmania, T. cruzi)

Trypomastigotes are also found in humans, but ARE mobile; They are found in blood/serum

26

Which stage of the protozoal flagellate life cycle is most likely to be found in the blood/serum of humans?

Trypomastigote

This is the form that is mobile in human blood
(T. cruzi, T, brucei)

Amastigotes are also found in humans, but are not mobile; They are found in tissues and macrophages

27

A patient's blood sample is positive for Trypanosoma bruci.

Which form/stage of its lifecycle is the protozoa in?

Trypanosoma; this is the stage that is found in the blood 

28

Which form of Trypanosoma spp. exist in the guts of their insect hosts?

Epimastigotes

(In general: epimastigotes and promastigotes are in flies, while amastigotes and trypomastigotes are in humans; not all protozoa take every form)

29

If a test question asks you about the life cycle stage of a hemoflagellate protozoa, what is a good rule of thumb to use?

  • In flies:
    • Epimastigote (replicative)
    • Promastigote (infective)
  • In humans:
    • Amastigote (immobile, in macrophages or tissues)
    • Trypomastigote (mobile, in bloodstream)

30

Which component of our immune system is most important in fighting helminths?

Eosinophils: Antibody-dependent cellular cytotoxicity