Exam 1: Mechanisms of Infection

Question 1

What viruses use the minor abrasion route?

Answer 1

Family: poxviridae

Cowpox, orf

Question 2

What viruses use the arthropod (mechanical) route?

Answer 2

Family: poxviridae

Fowlpox, swinepox

Question 3

What viruses use the arthropod (biological) route?

Answer 3

Family: rhabdoviridae

Bovine epheremal fever

Question 4

What viruses use the bite of vertebrate route?

Answer 4

Family: rhaboviridae

Rabies

Question 5

What viruses use the genital tract route?

Answer 5

Family: herpesviridae

Many species

Question 6

What viruses use the conjunctiva route?

Answer 6

Family: adenoviridae

Canine adenovirus 1 and 2

Question 7

What viruses initiate infection in the respiratory tract?

Answer 7

Adenoviridae and herpesviridae: many species

Parvoviridae: feline panleucopenia virus, canine parvovirus

Question 8

What viruses produce respiratory disease?

Answer 8

Adenoviridae and herpesviridae

Many species

Question 9

What viruses produce systemic disease, usually without initial respiratory signs?

Answer 9

Parvoviridae

Feline panleucopenia virus, canine parvovirus

Question 10

What viruses initiate infection in the intestinal tract?

Answer 10

Coronaviridae and toroviridae: some coronaviruses, Breda and Berne viruses
Calciviridae and picornaviridae: vesicular exanthema of swine virus, some enteroviruses

Question 11

What viruses produce diarrhea?

Answer 11

Coronaviridae and toroviridae

Some coronaviruses, Breda and Berne viruses

Question 12

What viruses produce systemic disease, usually without diarrhea?

Answer 12

Calciviridae and picornaviridae

Vesicular exanthema of swine virus, some enteroviruses

Question 13

What are the mechanisms of spread in the body?

Answer 13

Local spread on epithelial surfaces
Subepithelial invasion and lymphatic spread
Spread by the bloodstream: viremia

Question 14

Describe local spread on epithelial surfaces with pox virus

Answer 14

Produce infection via the skin

Local subepithelial and lymphatic spread

Question 15

Describe local spread on epithelial surfaces with paramyxoviruses and influenza virus

Answer 15

Do not invade subepithelial tissues

Enter lymphatic and spreaf

Question 16

Describe local spread on epithelial surfaces with rotaviruses or coronaviruses

Answer 16

Do not invade subepithelial tissues

Enter lymphatic and spread

Question 17

Where does canine distemper virus replicate?

Answer 17

Macrophages

Question 18

What is the most important route for virus shedding?

Answer 18

Respiratory secretions

Question 19

Which viruses have virus shedding in the skin?

Answer 19

FMD
Vesicular stomatitis
Pox
Herpes

Question 20

What viruses have virus shedding in saliva?

Answer 20

Rabies and feline immunodeficiency viruses

Question 21

What viruses have virus shedding in feces?

Answer 21

Poliovirus and rotaviruses

Question 22

What viruses have virus shedding in genital secretions?

Answer 22

Herpes and immunodeficiency viruses

Question 23

What viruses have virus shedding in urine (viruses that replicate in the kidney)?

Answer 23

Rinderpest
Infectious canine hepatitis
FMD

Question 24

What viruses have virus shedding in milk (replicate in mammary gland)?

Answer 24

Caprine arthritis-encephalitis

Tick-borne flaviviruses

Question 25

What happens to viruses that don't shed?

Answer 25

Replicate in CNS

Question 26

What viruses shed in the respiratory tract mucous membrane?

Answer 26

Canine distemper | Rinderpest

Question 27

What viruses shed in the skin?

Answer 27

Lumpyskin disease

Question 28

What viruses are in the brain, but no shedding?

Answer 28

Arbovirus | Canine distemper encephalitis

Question 29

What viruses shed in the salivary gland or kidney?

Answer 29

Rabies (salivary gland only) Arenaviruses Cytomegaloviruses

Question 30

What are persistent infections?

Answer 30

Infection that persist for the life of the animal, although episodes of clinical disease might occur infrequently

Question 31

What are examples of persistent infection?

Answer 31

Classical: herpesvirus Unclassical: canine distemper virus

Question 32

Why are persistent infections are important?

Answer 32

Serves as a source of infection for other animals Can be reactivated and cause recurrent acute episodes of disease Lead to immunopathologic disease Associated with neoplasms

Question 33

What are latent infections?

Answer 33

Virus is not demonstrable except when reactivation occurs

Question 34

What are chronic infections?

Answer 34

Virus always demonstrable and often shed and disease may be absent, chronic, or may develop late

Question 35

What are slow infections?

Answer 35

Virus gradually increases during a very long preclinical phase, leading to a slowly progressive lethal disease

Question 36

Where does the viral genome for infectious bovine rhinotracheitis virus persist?

Answer 36

Latently in neurons, probably as an episome

Question 37

What happens when the episome for infectious bovine rhinotracheitis virus reactivates?

Answer 37

Infectious virus is produced and moves down the sensory nerves and reaches the nasal mucous membrane or the skin

Question 38

Where does proliferation of infectious bovine rhinotracheitis virus occur?

Answer 38

Epithelial cells, with virus shedding

Question 39

What is an episome?

Answer 39

Like an extracellular plasmid

Question 40

What does FMD persist in?

Answer 40

The pharynx in cattle, sheep, goats, and other ruminants

Question 41

What is lymphocytic choriomenigitis in mice caused by?

Answer 41

Arenavirus

Question 42

How is lymphocytic choriomenigitis in mice transmitted?

Answer 42

Horizontally and in utero

Question 43

What is vertical transmission?

Answer 43

Offspring becomes immunologically tolerant (in presence of virus but in absence of antibody)

Question 44

What is immunological tolerance (incomplete)?

Answer 44

The presence of virion-IgG-complement and the complexi is infectious

Question 45

What is subacute spongiform viral encephalopathies?

Answer 45

Scrapie in sheep and goats | Bovine spongiform encephalopathy (Mad cow)

Question 46

What are prions?

Answer 46

Proteinaceous infectious particles | Misfolded protein that concentrates in the tissues of CNS

Question 47

Where do prions concentrate?

Answer 47

In brain and spinal cord

Question 48

What are prions resistant to?

Answer 48

Steam sterilization

Question 49

What do prions do?

Answer 49

Persuades other proteins to copy it

Question 50

What is canine distemper?

Answer 50

Acute systemic infection in which the majority of dogs recover completely within 1 month

Question 51

What can happen with dogs that have recovered from canine distemper?

Answer 51

They can harbor the virus in brain cells where it replicates slowly and eventually produces old dog encephalitis

Question 52

What is the pathogenesis of persistent infections?

Answer 52

``` Unique properties of the virus: Nonimmunogenic agents Integrated genomes Growth in protected sites Antigenic variation ```

Question 53

Describe nonimmunogenic agents-prions

Answer 53

Do not induce interferon | No immune responses, therefore host cannot restrict the replication and pathologic effects

Question 54

What are integrated genomes?

Answer 54

Retroviruses whose proviral DNA is integrated are maintained indefinitely, from one generation to the next, as a part of the genome of the host

Question 55

Describe how alphaherpeeviruses grow in protected sites

Answer 55

Avoid immune elimination by remaining within cells of the nervous system As episomal DNA in ganglion cells during the intervals between disease episodes As viral DNA, subviral particles, or virions within axons prior to acute recurrent episodes

Question 56

Describe how betaherpeeviruses and gammaherperviruses grow in protected sites

Answer 56

Avoid immune elimination by maintaining serial infection by cell-to-cell contact

Question 57

What are mechanisms of modification of host defense?

Answer 57

Defective antibody response Defective cell-mediate immunity Growth in macrophages

Question 58

In defective antibody responses, what do viruses that replicate in lymphoid tissue and macrophages do?

Answer 58

Induce non-neutralizing antibodies

Question 59

What does the antibody do in defective antibody response?

Answer 59

Combines with viral antigens and virions in the serum to form immune complexes which may produce immune complex disease

Question 60

What do viruses in macrophages do?

Answer 60

Avoid host immune responses

Question 61

Describe defective cell-mediated immunity

Answer 61

Immunosuppresion by the causative virus Immunological tolerance The presence of virus-antibody complexes Filaure of immune lymphocytes to reach target cells Decrease in the numbers of Th lymphocytes

Question 62

What is the target of receptor analogs?

Answer 62

Attachment of virion to cell receptor

Question 63

What is the target of transcriptase inhibitor?

Answer 63

Primary transcription

Question 64

What is the target of AZT?

Answer 64

Reverse transcription

Question 65

What is the target of interferons?

Answer 65

Translation of viral mRNA into protein

Question 66

What is the target of protease inhibitors?

Answer 66

Post-translational cleavage of proteins

Question 67

What is the target of replicase inhibitors?

Answer 67

Replication of RNA viral genome