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2024 VIROLOGY > Lesson 2 > Flashcards

Lesson 2 Flashcards

1
Q

the production of disease as a result of viral infection, is concerned with the cellular events and pathological mechanisms that connect the
virus to cell/tissue/organ damage and the resulting clinical signs.

A

Viral pathogenesis

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2
Q

refers to the relative ability of viruses to produce disease in a host, dependent on the attributes of both the virus and its host, and is influenced by
factors such as the dose and route of entry of the virus and the species, age and
immune status of the host.

A

Virulence

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3
Q

Routes of infection:

A

 Skin: Breaks in skin epithelia
 Respiratory tract: Mucous membranes
 Alimentary tract: through ingestion, some resp. viruses enter the oral cavity by
ciliated epithelium
 Genital tract: abrasion in urethral, anal or vaginal mucosa (venereal tumors)
 In utero (congenital diseases)

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4
Q

Stages of viral infection

A
  1. Initiation of Infection at Primary Site (Infection of the Target Tissue)
  2. Replication of Virus and Spread to Secondary Site
  3. Manifestations of the viral diseases
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5
Q

many viruses cause infection in the oral mucosa or upper respiratory tract. Replication of viruses at the primary sites may be accompanied by clinical symptoms.

A

Initiation of Infection at Primary Site (Infection of the Target Tissue

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6
Q

many viruses cause infection in the oral mucosa or upper respiratory tract. Replication of viruses at the primary sites may be accompanied by clinical
symptoms.

A

Initiation of Infection at Primary Site (Infection of the Target Tissue

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7
Q

Some viruses may disseminate to other tissues through blood stream, lymphatic system, and
neurons (secondary sites) and cause a systemic infection. Transport of virus in the blood is known as viremia. Primary viremia is when the virus enters the blood stream after multiplication in the lymph nodes. In the blood stream, the
virus may exist either free in the plasma or it may be ingested by the lymphocytes or macrophages. When virus replicate in the macrophages, in the endothelial lining of blood vessels, or in the spleen and liver it will result in
20 massive production of viruses causing secondary viremia signaling the onset of
clinical signs, after which the virus will be carried to the target organs to further replicate and produce characteristic distinctive lesions.

A

Replication of Virus and Spread to Secondary Site

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8
Q

Some viruses may disseminate to other tissues through blood stream, lymphatic system, and
neurons (secondary sites) and cause a systemic infection. Transport of virus in the blood is known as viremia. Primary viremia is when the virus enters the blood stream after multiplication in the lymph nodes. In the blood stream, the
virus may exist either free in the plasma or it may be ingested by the lymphocytes or macrophages. When virus replicate in the macrophages, in the endothelial lining of blood vessels, or in the spleen and liver it will result in
20 massive production of viruses causing secondary viremia signaling the onset of
clinical signs, after which the virus will be carried to the target organs to further replicate and produce characteristic distinctive lesions.

A

Replication of Virus and Spread to Secondary Site

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9
Q

___________________ Manifestations of the viral diseases: dependent on the virulence of the virus
and host factors:

A

Manifestations of the viral diseases
a) Age, general health and immune status of the host
b) Dose of infective virus
c) Genetics of host and the virus.

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10
Q

 Incubation period: is the time taken by the virus to spread from the site
of entry to the organs of viral replication and then to the target organs for
production of lesions. In local infections, incubation period may be short
(1-3 days) because site of entry of the virus and lesions are the same, however systemic infections may have longer incubation periods (usually
10-20 days) because lesions are produced far from the site of entry

A
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11
Q

Severity of viral infections:
 inapparent infection: causes;

A

(a) the infection is controlled before the virus reaches the target tissues,
(b) the infected tissue is not damaged,
(c) the tissue is damaged but it is rapidly repaired, or
(d) the severity of damage is below a functional threshold for the particular disorder

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12
Q

: occurs when immune system acts rapidly to
control the infection

A

acute infection

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13
Q

when the immune system fails to act effectively or slowly, it may result in chronic viral disease or 21 persistent viral infection in the case of slow viruses that takes years before progressing to manifestation of the disease.

A

chronic or persistent infection

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14
Q

Incubation period

A
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15
Q

Types of host cell in terms of virus-host interaction

A
  1. Permissive cell
  2. Nonpermissive cell
  3. Semipermissive cell
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16
Q

Types of virus infection at cellular level:

A
  1. Abortive infection
  2. Lytic infection
  3. Persistent viral infection
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17
Q

failed infection

A

Abortive infection

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18
Q

results to cell death

A

Lytic infection

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19
Q

infection without cell death

A

Persistent viral infection

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20
Q
  1. Persistent viral infection: infection without cell death
A

a) nonlytic and productive (chronic),
b) latent, limited production of viral macromolecules in the absence of
synthesis of virus
c) recurrent
d) transforming

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21
Q

Mechanisms used by virus to cause cell death

A
  1. Inhibition of cellular protein synthesis
  2. Cell fusion
  3. Transformation
  4. Cytopathic effect
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22
Q

during replication produce proteins that inhibit synthesis of cellular DNA and/or RNA.

A

Inhibition of cellular protein synthesis: (ex: HSV, poliovirus, togaviruses, and poxviruses)

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23
Q

Inhibition of cellular protein synthesis example:

A

ex: HSV, poliovirus, togaviruses, and
poxviruses

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24
Q

: Infections of cells with certain viruses results in the expression of glycoproteins on the cell surface causing the cells to fuse, g in the production of giant multinucleated cells called syncytia (ex: paramyxoviruses, herpes viruses, and retroviruses)

A

Cell fusion

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25
Q

g in the production of giant
multinucleated cells called

A

syncytia

26
Q

Cell fusion example

A

paramyxoviruses, herpes viruses, and
retroviruses

27
Q

: an irreversible genetic process caused by the integration of viral
DNA with the DNA of the host cell transforming normal cells to malignant cells.

A

Transformation

28
Q

The viruses that stimulate uncontrolled cell growth causing the transformation of
immortalization of the cell are known as

A

oncogenic viruses

29
Q

Cytopathic effect:
Demonstration of inclusion bodies is characteristic of a particular viral infection; presence of such bodies facilitates laboratory diagnosis:

A

Negri bodies
Guarnieri bodies
Bollinger bodies
Molluscum bodies

30
Q

are the intracytoplasmic eosinophilic inclusion bodies in the neural cells and are pathognomonic of rabies.

A

Negri bodies

31
Q

are small, multiple inclusions found in vaccinia-infected cells.

A

Guarnieri bodies

32
Q

are large inclusions seen in fowl pox.

A

Bollinger bodies

33
Q

are very large inclusion bodies seen in the molluscum contagiosum infected cell.

A

Molluscum bodies

34
Q

virus is either free in the plasma (ex: parvovirus or picornavirus) or associated with circulating cells (ex: Marek’s disease virus, canine distemper virus) and is passively transported into distant sites of the body to settle and replicate.

A

Haematogenous spread

35
Q

Read clinical signs of virus infection

A
36
Q

also occurs when older animals are more susceptible to infections than younger animals.

A

Reverse age resistance

37
Q

Abortion following viral infection is usually indicative of substantial damage to the tissues of the placenta or foetus. The effect on the foetus is often influenced by the stage of gestation and by the virulence of the virus:

A

 Infection early in gestation - results in foetal death (resorption or abortion)
 Infection occurs at a later stage - results to congenital defects
 Infection towards the end of pregnancy - induces a protective immune response

38
Q

 results in foetal death (resorption or abortion)

A

Infection early in gestation

39
Q

 - results to congenital defects

A

Infection occurs at a later stage

40
Q

 induces a protective immune response

A

Infection towards the end of pregnancy -

41
Q

Viral shedding
The shedding of infectious virions from surfaces or orifices via aerosols, droplets, scabs, body fluids, excretions and secretions (saliva, blood, semen, milk, urine, faeces) allows transfer to other susceptible hosts which usually coincides with the onset of clinical signs or may begin earlier in some viral infections.

A
42
Q

Routes by which viruses are shed

A

:1. Coughing and sneezing: transmit virus in aerosol
2. Faeces: sheds enteric viruses
3. Body fluids such as saliva, semen, urine and milk may contain particular viruses
4. Arthropod vectors for arboviruses
5. Surgical procedures for some blood-borne viruses
6. Transplacental route or via birth canal
7. DNA of germ cells

43
Q

 present shedding of large amounts of virus over a short period. These viruses are either highly contagious (influenza virus) or capable of surviving for long periods in the environment (ex: parvoviruses, poxviruses and many enteric viruses).

A

Acute infection

44
Q

 present constant or intermittent shedding at low levels. Infections of this type, produced by lentiviruses, jaagsiekte sheep retrovirus and prions, have a progressive clinical course, usually resulting in death.

A

Persistent or chronic viral infections

45
Q

 are characterized by persistence of the virus in a nonproductive form, either integrated into the genome of the host (ex: retrovirus, or as an episome, in the case of herpesviruses).

A

Latent infections

46
Q

 with shedding of infectious virus may occur (ex: alphaherpesviruses, such as feline herpesvirus 1, which produce productive infections in epithelial cells and latent infections in sensory neurons).

A

Periodic reactivation of productive infection

47
Q

 Geographical Distribution - depends on the following factors:

A

(a) the presence of vectors for the transmission of disease
(b) cofactors facilitating the transmission of disease, and
(c) the presence of susceptible population in the particular area.

48
Q

The viral infection in a community may occur as an

A

Outbreak
Epidemic
Pandemic

49
Q

: occurs from a common source, for example, infected food, and is seen only in clusters of people

A

Outbreak

50
Q

: occurs due to introduction of a new strain of virus into an immunologically susceptible population, e.g., influenza epidemic

A

Epidemic

51
Q

: resulting from introduction of a new strains virus, e.g., HIV

A

Pandemic

52
Q

 Reservoir and Sources of Infection

A

(a) Human reservoir
(b) Animal reservoir
(c) Arthropod-vectors
(d) Asymptomatic patients

53
Q

usual reservoir, serves as source of infection for other susceptible hosts

A

Human reservoir

54
Q

usual reservoir, serves as source of infection for other susceptible hosts

A

Human reservoir

55
Q

(c) : some arthropods act as vectors for transmission of viruses (arboviruses)

A

Arthropod-vectors

56
Q

are also important source of infection, virus are shed before the onset of clinical signs

A

Asymptomatic patients

57
Q

 Transmission - depends on the following factors:

A

(a) The site of viral replication and secretions: ex: enteric viruses are excreted in the feces and are transmitted by fecal–oral route (e.g., picornavirus and reovirus). Respiratory viruses are secreted in aerosol droplets, hence are transmitted by inhalation.
(b) Presence or absence of envelope in the viruses:

58
Q

Presence or absence of envelope in the viruses:

A

i. enveloped viruses: envelope must be intact to retain infectivity; they are usually transmitted by respiratory droplets, saliva, mucus, blood or semen, organ transplantation, and by ingestion, instead of fecal–oral route where they can be destroyed rapidly in the gastrointestinal tract of the infected humans/animals due to presence of acid (except Hepatitis B virus and coronavirus).
ii. naked viruses: nonenveloped viruses are sturdy viruses which can resist drying, extremes of pH and temperature, and the effects of detergents. Therefore, these viruses are generally transmitted by the respiratory and fecal–oral routes and also often by contaminated objects (fomites).

59
Q

envelope must be intact to retain infectivity; they are usually transmitted by respiratory droplets, saliva, mucus, blood or semen, organ transplantation, and by ingestion, instead of fecal–oral route where they can be destroyed rapidly in the gastrointestinal tract of the infected humans/animals due to presence of acid (except Hepatitis B virus and coronavirus).

A

enveloped viruses:

60
Q

nonenveloped viruses are sturdy viruses which can resist drying, extremes of pH and temperature, and the effects of detergents. Therefore, these viruses are generally transmitted by the respiratory and fecal–oral routes and also often by contaminated objects (fomites).

A

Naked viruses

61
Q

 Prevention of Viral Diseases

A

(a) Adoption of good hygiene
(b) control of the vectors
(c) by immunization of the population (herd immunity via vaccines)

62
Q

are defined as viruses maintained in nature through biological transmission between vertebrate hosts by haematophagous arthropods. The viruses multiply in the tissues of the arthropod vector (ex: mosquitoes, ticks, sandflies and midges) which remains infected for life. Domestic animals and humans are generally ‘deadend’ hosts as they do not develop sufficient viraemia to contribute to the transmission of the virus.

A

Arboviruses: (arthropod-borne viruses)

2024 VIROLOGY (23 decks)

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