Pathogenesis of veterinary respiratory viruses

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Pathogenesis of veterinary respiratory viruses

• PETER H. RUSSELL, BVSc, PhD, FRCPath, MRCVS
• Department of Pathology and Infectious Diseases,
  The Royal Veterinary College,
• Royal College Street,
• London NW1 OTU.
• E-mail Web site

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ObjectivesStudents should be able to

• 1. explain how some viruses spread within the
  respiratory tract whereas others leave it to
  cause disease elsewhere.
• 2. describe in outline how host responses,
  vaccines and maternal antibody influence
  pathogenesis.
• 3. evaluate how to determine whether a
  respiratory tract virus is a primary pathogen or
  whether it exacerbates bacterial disease or does
  nothing.
• 4. compare and contrast acute and chronic virus
  infections of the respiratory tract.

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Objective 1. explain why some viruses spread
within the respiratory tract whereas others leave
it to causedisease elsewhere.
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Lesions and location

• Lesions are erosions and inflammation. Secondary
  bacterial infection of the erosions causes
  mucopurulent exudate.

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Disease is compounded by stress whether crowding,
transport or social. The contact allows more
interchange of viruse eg Battersea dogs home.
The stress reactivates viruses eg herpesviruses
or increases virus excretion eg feline
caliciviruses. Think of examples for calves,
pets, horses.
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Objective 2. describe in outline how host
responses, vaccines and maternal antibody
influence pathogenesis.
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Antigenic variation can explains vaccine failures
when a new isolate of the same virus arrives eg
when the 1998 USA-like strain of equine influenza
II (H3N8)entered the UK. Variation can mean
vaccines partially protect eg with feline
calicivirus. These cats can be silent carriers
of the antigenically-distinct FCV and then can
enter a cattery undetected and cause lesions in
unvaccinated cats (cf FMDV).
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How do dead subcut vaccines protect? Via
circulating IgG which leaks into the inflamed
resp tract
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Objective 3. evaluate how to determine whether a
respiratory tract virus is a primary pathogen or
whether itexacerbates bacterial disease or does
nothing
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Objective 4. Compare and contrast acute and
chronic virus infections of the respiratory
tract.
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Objective 4. Compare and contrast acute and
chronic virus infections of the respiratory tract
(Cont.)
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Further reading
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Further reading (Cont.)
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Your ideas please! Key words, Koch postulates,
germ free animals,
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