L18: Veterinary Virology (Waltzek) Flashcards
virus
obligate intracellular pathogens that are unable to direct any biosynthetic processes outside the host cell
-smaller and simpler than bacteria
do viruses have functional ribosomes?
no
Edward Jenner
used cowpox to vax for smallpox
Louis Pasteur
“father of microbiology”
-developed rabies vax, pasteurization
first pig epizootic
swine influenza; discovered by Shope in 1931
Koch’s postulates
- agent must be present in every case of dz
- agent must be isolated from the host and grown in vitro
- dz must be reproduced when the pure cultivated agent is introduced into a healthy susceptible host
- same agent must once again be recoverable from the newly infected host
virales refers to
order
viridae refers to
family
virinae refers to
subfamily
virus refers to
genus
how are viruses classified?
- architecture
- nucleic acid
- phylogenomics
- antigenic relationships (serology)
- biologic characteristics
what is a virion?
completed infectious virus particle
-contains nucleocapsid +/- host-derived envelope
nucleocapside
nucleic acid (RNA or DNA) core enclosed in protein coat (capsid)
what is virus envelope composed of?
glucoprotein studded phospholipid membrane
which are more durable: enveloped or non-enveloped viruses?**
non-enveloped
-survive better outside host and less susceptible to disinfectants
types of nucleocapsid shapes
symmetrical (icosahedral, heical)
non-symmetrical (complex, filamentous, pleomorphic)
icosahedral nucleocapsid
has 20 equilateral triangular faces (i.e. FMDV, rhabdoviruses)
helical nucleocapsid
coiled appearance (i.e. rabies)
complex nucleocapsid
i.e. smallpox
filamentous nucleocapsid
thread-like i.e. ebola
Types of viral nucleic acids
dsDNA ssDNA dsRNA ssRNA *all must make mRNA --> translation --> proteins --> virus
viruses with dsDNA genomes
(Class I viruses) Papillomaviridae (papillomaviruses) Adenoviridae (adenoviruses) Herpesviridae (bovine/equine herpesvirus, porcine cytomegalovirus) Poxviridae (poxviruses) Asfaviridae (African swine fever virus)
viruses with ssDNA genomes
(Class II viruses)
Circoviridae (porcine circovirus)
Parvoviridae (canine parvovirus, feline panleukopenia, porcine parvo)
viruses with dsRNA genomes
(Class III viruses)
Reoviridae (rotaviruses, bluetonge virus, african horse sickness)
Birnaviridae (infectious bursal disease, infect. pancreatic necrosis)
role of phylogenetics
confirms previously established taxononic schemes based on virion architecture, NA type, etc.
ex. of antigenic relationships (serology)
how host mounts immune response to viral proteins Hemagglutinin (H) and Neuraminidase (N)
viruses with ssRNA(+) Genomes
(Class IV viruses)
Picornaviridae (foot/mouth dz, porcine enteroviruses)
Caliciviridae (feline calicivirus)
Coronaviridae (feline coronaviruses)
Arteriviridae (equine arterivirus)
Flaviviridae (pestiviruses, flaviviruses)
Togaviridae (alphaviruses)
viruses with ssRNA(-) Genomes
(Class V viruses)
Orthomyxoviridae (influenza)
Paramyxoviridae (parainfluenza, distemper, resp. syncytial)
Rhabdoviridae (rabies, vesicular stomatitis)
Filoviridae (ebola)
Bunyaviridae (Haantan virus)
viruses with Reverse Transcriptase
(Class VI and VII)
Retroviridae (feline leukemia, feline/bovine immunodeficiency, bovine/avian leukosis viruses, caprine arthritis-encephalitis virus)
Hepadnaviridae
grouping of viruses on the basis of biologic properties is based on
virus tropisms and modes of transmission
Categories:
-enterics, respiratory viruses, arboviruses, oncogenic viruses
generalized viral life cycle
attachment penetration uncoating replication transcription translation assembly release
virus induced cellular changes
necrosis/apoptosis (Cytopathic Effect)
cell transformation (i.e. –> neoplasia)
no discernible effect
which viruses are shed at SURFACE of skin, mm, resp. tract, GIT
herpes
papillomavirus
Which viruses are shed in blood?
hepatitis B
poliovirus
HIV
enteric viruses
-usually acquired by ingestion (fecal/oral)
-replicate primarily in intestines
Examples:
-Picornaviridae
-Caliciviridae
-Astroviridae
-Coronaviridae
-Reoviridae
-Parvoviridae
-Adenoviridae
Respiratory viruses
-acquired by inhalation and replicate in resp. tract Examples: -Picornaviridae -Caliciviridae -Coronaviridae -Paramyxoviridae -Orthomyxoviridae -Adenoviridae
Arboviruses
-undergo a natural vector-vertebrate-vector cycle
-replicate in host, transmitted by arthropod
Examples:
-Togaviridae, Flaviviridae, Rhabdoviridae, Bunyaviridae, Reoviridae
Oncogenic viruses
-acquired by close contact, injection, fomites, sex. contact
-usually only infect specific cells in target tissues, and may transform these cells –> neoplasia
Examples:
-Retroviridae
-Hepadnaviridae
-Papillomaviridae
-Adenoviridae
-Herpesviridae
