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Hepatic viruses Flashcards

1
Q

Explain why infectious agents affect the liver

A
  • Major organ encountered in line after penetration of gut (via portal vein)
  • Major organ that filters blood directly from heart
  • Easy to get there and establish infection
  • Liver provides hepatocyte-specific cofactors/nutrients to pathogens
  • Liver micro RNAs can drive irus RNA replication
  • Ineffective host anti-viral immune response in liver
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2
Q

Give an example of how the liver provides liver-specific cell cofactors/nutrients

A
  • High arginine requirement of hepatotropic adenoviruses
  • Arginine rich proteins in the liver
  • Arginine supplied to hepatotropic adenoviruses
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3
Q

Explain how liver micro RNAs can drive virus RNA replication

A
  • Via activation of viral RNA 3’ untranslated region
  • Human hep C infection using micro-RNA 122
  • Micro-RNAs are non-cpding regions of genomes, expressed in tissue specific way
  • Regulate gene expression
  • Viruses hijack this for own RNA replication and regulation
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4
Q

List the principle outcomes of virus or pathogen infection in the liver

A
  • Acute or chronic hepatitis
  • Sometimes with hepatomegaly
  • Cytotoxic T cell and NK cell mediated damage
  • Dysregulation of normal liver function (jaundice, hypoproteinaemia, hypoglycaemia, anaemia)
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5
Q

What are the 2 types of hepatic virus?

A
  • Those affecting the liver predominantly (CA-1 of ICH)

- Those targeting the liver as part of generalised systemic infection

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6
Q

What is the majority of liver damage in infection caused by?

A
  • Some due to the pathogen/virus
  • most due to immune response to infected cells
  • Cytotoxic lymphocytes dysregulated by infection causing tissue damage
  • Excess host immune response to infectious agent
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7
Q

What type of hepatic virus causes canine hepatitis and name the causative agent

A
  • Hepatotropic virus (those principally affecing the liver)

- Canine adenovirus type 1

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8
Q

Describe the pathogenesis of canine hepatitis

A
  • Can cause periacinar necrosis (arouns around centre of lobules)
  • Tropism for endothelium (widespread haemorrhages, particular of serosal surface and hepatocytes)
  • Recovering animals may show immune mediated uveitis with corneal opacity
  • Damage to blood vessels leading to haemorrhage
  • Tissue damage mostly caused by host immune response, only some caused by virus
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9
Q

Describe the epidemiology of canine hepatitis

A
  • Highly infectious disease of young dogs
  • Spread via uriine of infected animals over long period of time
  • Contagious disease of dogs, occurs worldwide
  • Mortality highest in puppies
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10
Q

Describe how an animal becomes infected with canine hepatitis

A
  • Ingestion of urine, saliva, faeces from infected animal
  • Replicates in tonsils, larynx, Peyer’s patches as primary sites
  • Progresses to liver, eyes, kidneys for secondary replication
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11
Q

Describe the clinical signs of canine hepatitis

A
  • Apathy
  • Anorexia
  • Thirst
  • Conjunctivitis
  • Ocular and nasal discharge
  • Abdominal pain
  • Vomitign
  • Blood clotting affected, leads to haemorrhages in affected tissues (gums for example)
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12
Q

Describe the appearance of a liver affected by canine hepatitis

A
  • Areas of necrosis

- Adenoviral inclusion bodies in nuclei of Kupffer cells and parenchymal cells

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13
Q

Describe canina adenovirus type 1

A
  • Causative agent of canine hepatitis
  • Adenoviridae family
  • Non-enveloped
  • Linear double stranded DNA
  • Icosahedral
  • Capsid consists of hexons and pentons, fibres protrude from these that contain cell attachment roteins
  • Virus replicates in nuelcieus of host cells
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14
Q

Describe the immune response to canine hepatitis

A
  • Survivors immune to reinfection

- Solid immune response

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15
Q

Describe the control of canine hepatitis

A

Live attenuated virus or killed virus vaccine

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16
Q

What causes the “blue eye” opacity seen in canine hepatitis?

A
  • Host immune resopnse

- Caused by immune complex deposition in glomeruli of kidney and cornea in eyes

17
Q

What is the causative agent of malignant catarrhal fever in cattle/deer?

A
  • 2 viruses
  • Alceaphine herpesvirus 1 (AIHV-1, reservoir in wildebeest, found in Africa)
  • Ovine herpesvirus-2 (OvHV-2, reservoir in sheep, worldwide)
18
Q

What type of virus causes malignant catarrhal fever?

A

One that cuases systemic disease that includes liver pathology

19
Q

Describe the pathogenesis of malignant catarrhal fever

A
  • Lympho-proliferation and tissue necrosis
  • Infection of natural host (sheep, wildebeest) no disease
  • Infection of disease-susceptible host (cattle, deer, bison, pigs) erratic infection, results in dramatic pathological changes and death
  • Virus invades cells
  • Destroys epithelium and endothelium
  • OvHV-2 infects via oro-nasal pharyngeal port of entry
  • Gets into lymphocytes
  • Presence of virus in ytotoxic T/NK cells associated with indiscriminate (non-MHC-linked) destruction of tissues
  • Vasculitis and epithelial damage in multiple tissues causes death
20
Q

Describe the clinical signs of malignant catarrhal fever

A
  • Fever, depression, lack of appetite
  • Nasal discharge
  • Conjunctivitis and corneal opacity
  • Lymph node hyperplasia
  • Lesions in mouth and GIT
  • Lesions in skin and muzzle
  • Lesions in CNS
  • Death (recovery rare)
21
Q

Describe the presence of malignant catarrhal fever in British/European cattle

A
  • Relatively resistant

- Sporadic infection, only affects a few at a time

22
Q

Describe the transmission of malignant catarrhal fever

A
  • All lambs have virus within 2 months of age
  • Peak excretion around 7-10 moths, no disease
  • Spreads from sheeo to cattle
  • Can be spread via humans
  • NO horizontal transmission between cattle
23
Q

Explain why transmission of malignant catarrhal fever is not possible between cattle

A
  • Virus undergoes incomoplete replication cycle
  • No enveloping
  • Cannot escape cells and be excreted
24
Q

Describe the control of malignant catarrhal fever

A
  • No vaccine
  • Avoid having sheep and cattle together
  • Maintain high biosecurity humans going between sheep and calves

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