Transcript HERPESVIRIDAE

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
Objectives
Students 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.
Objective 1. explain why
some viruses spread within
the respiratory tract
whereas others leave it to
cause
disease elsewhere.
Lesions and location
Lesions are erosions and
inflammation. Secondary bacterial
infection of the erosions causes
mucopurulent exudate.
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.
Objective 2. describe in
outline how host responses,
vaccines and maternal
antibody influence
pathogenesis.
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 antigenicallydistinct FCV and then can enter a cattery
undetected and cause lesions in
unvaccinated cats (cf FMDV).
How do dead subcut
vaccines protect? Via
circulating IgG which leaks
into the inflamed resp tract
Objective 3. evaluate how
to determine whether a
respiratory tract virus is a
primary pathogen or
whether it
exacerbates bacterial
disease or does nothing
Objective 4. Compare and
contrast acute and chronic
virus infections of the
respiratory tract.
Objective 4. Compare and
contrast acute and chronic
virus infections of the
respiratory tract (Cont.)
Further reading
Further reading (Cont.)
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Your ideas please!
Key words, Koch postulates,
germ free animals,
)
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