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Foundations of Medicine > Viruses and Fungi and Parasites > Flashcards

Viruses and Fungi and Parasites Flashcards

1
Q

What is a virus?

A

A virus is non-cellular and can only replicate in a living host cell.

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2
Q

What is a virion?

A

A virus outside a cell which facilitates its transmission from one host to another. It is a genome surrounded by a protein coat.

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3
Q

How are viruses transmitted?

A 
Blood borne 
Sexual 
vertical 
Faecal-oral 
Droplet
Airborne 
Close contact 
Vector-Borne
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4
Q

What is reactivation of a virus?

A

Some viruses are able to live within the host for a long period of time in there dormant state. Re-infection occurs when a virus comes out of this dormant state. It may or may not cause disease symptoms but is more likely to happen in the immunocompromised.

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5
Q

How can viral transmission be prevented?

A

Immunisation
prophylactic treatment post exposure
Infection prevention and control measures
Antenatal screening

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6
Q

What would make a virus suitable for potential eradication?

A 
Clearly identifiable 
No animal reservoir 
No amplification in the environment 
Practical and effective intervention 
Government support
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7
Q

What four ways are viruses classified using?

A

Species, Genus, family and order

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8
Q

How is a viral infection detected?

A

Using the whole organism - Microscopy or culture
Using part of the organism - Antigen detection
Immune response - Antibodies

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9
Q

How is a viral infection treated?

A

In a minority of cases antiviral therapy

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10
Q

What are the challenged of antiviral drugs?

A

Hard to target the virus without targeting part of the host
They only inhibit (virustatic) the virus rather than killing (virucidal)
They can only be used in a minority of cases

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11
Q

What are the different types of antiviral drugs?

A

Prophylaxis - Prevent infection
Pre-emptive - Infection has started but symptoms haven’t
Overt disease of suppressive therapy - Keep viral replication low to prevent symptoms despite infection

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12
Q

What are the three shapes that viruses can be?

A

Icosahedral
Helical
Complex

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13
Q

Do antibiotics work against virus?

A

Not at all

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14
Q

Key words

A 
Icosahedral 
Helical 
Complex
virustatic
virucidal
Aciclovir
Valaciclovir 
Ganciclovir
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15
Q

How can herpes virus be treated?

A

Anti-herpes virus drugs. More effective in some and better results if started early on.

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16
Q

What is Aciclovir used for ?

A

Herpes Simplex and Varicella Zoster virus etc. It must be converted to an active from before use. It is good at killing infected cells and leaving other cells alone.

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17
Q

What are another two examples of antiviral drugs?

A

Valaciclovir

Ganciclovir

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18
Q

How is hepatitis treated?

A

Ribavirin, Adefovir, Dipivoxil, lamivudine

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19
Q

What are fungi ?

A

Eukaryotes that from spores and lack chlorophyll.

20
Q

Describe the structure of fungi

A

Polysaccharide wall and absorb nutrient. Membrane contains ergosterol.

21
Q

How are fungi diagnosed?

A

Morphology through histopathology, also CT scans, detection of antigens, detection of antibodies etc

22
Q

What are the classifications of fungi?

A

Ascomycetes, Basidiomycetes and zygomycetes.

23
Q

How are fungi treated?

A

Antifungal drugs are new and not very good. There are three types polyenes, Azoles, Echinocandins.

24
Q

Key words from fungi

A 
Ascomycetes, 
Basidiomycetes 
Zygomycetes
Polyenes, 
Azoles, 
Echinocandins. 
Amphotericin B
25
Q

Example of fungal infections

A

Dermatophyte - Skin, mucous membrane , hair, nails etc causes ringworm

26
Q

How do polyenes work?

A

Polyenes bind to the fungal cell wall and increase permeability.

27
Q

How do amphotericin B work?

A

It is the only antifungal suitable for IV and treats systemic fungal infection. A type of polyene.

28
Q

How does nystatin work?

A

Topical use only. A type of polyene.

29
Q

What is a parasite?

A

An organism that lives in or on another organism and derives its nutrients at the expense of the host.

30
Q

Parasites can be …. ?

A

Vectors of infection - An organism which acts as an intermediate host moving a parasite from one host to another
Infection causing

31
Q

What are the three classes of parasite?

A

Protozoa
Helminths
Ectoparasites

32
Q

What are protozoa?

A

Microscopic, single celled organisms that are able to multiple in humans. They can be free living or parasitic.

33
Q

How are endo and exo protozoa transmitted?

A

Endo-protozoa can be transmitted through faecal -oral route

Exo-protozoa can be transmitted through a insect vector.

34
Q

What are the three examples of protozoa infections

A

Malaria
Amoebae
Flagellates

35
Q

What is malaria?

A

Malaria is caused by the plasmodium parasite which is transmitted from one human to another by anopheles mosquitoes. There are five types of plasmodium but P. Falciparum has the highest mortality.

36
Q

What is the life cycle of plasmodium?

A

An infected mosquito, acting as a vector,
bites a human. Plasmodium enters the
human bloodstream. Asexual reproduction
occurs in the liver and then in the red blood
cells. When the red blood cells burst
gametocytes are released into the
bloodstream. Another mosquito bites an
infected human and the gametocytes enter
the mosquito, maturing into male and female
gametes, allowing sexual reproduction to
now occur. The mosquito can then infect
another human host.

37
Q

How does malaria present?

A

Fever, chills, flu like illness.

38
Q

What is amoebic dysentery?

A

Entamoeba histolytica protozoan infection which invades the gut wall and causes bloody diarrhoea. It can also cause liver abscess in late disease. Under the microscope you can see cysts in the formed stool. Transmitted the faecal-oral route.

39
Q

What are the three types of helminths?

A

Nematodes (round worm)
Cestodes (Tapeworm)
Trematodes (flatworm)

40
Q

What is enterobiasis?

A

Type of nematode. Caused an anal itch especially at night and is transmitted via the faecal-oral route. It is not harmful be can disturb sleep.

41
Q

What is ascaris lumbricoides?

A

Type of nematode. Causes failure to thrive in children and may obstruct the small intestine or common bile duct. Transmission is faecal -oral route.

42
Q

What is Taenia saginata and taenia solium?

A

Cestodes found in beef and pork. Transmission occurs when eating undercooked meat.

43
Q

What is echinococcus sp.?

A

Carried by dogs, wolves and foxes. Cause hydatid cysts in the liver which must be surgically resected.

44
Q

What is schistosomiasis ?

A

There are three main types S. Hae…. S.Man…. and S.Jap…. It can cause liver failure and bladder cancer.
Schistosomes reproduce sexually in the
human intestine. The fertilised eggs pass out
via faeces into water where they develop into
larvae. The larvae then infect water snails,
where asexual reproduction occurs. This
produces another type of motile larvae, which
escape the snail and penetrate the skin of a
human, entering the bloodstream

45
Q

What are ectoparasites?

A

Parasites which live on the surface of a host. They are mainly insects or arachnids and many are vectors.

Foundations of Medicine (25 decks)

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