Keypoints - Viruses Flashcards
Poxviridae Key Points
Key points
Enveloped DNA viruses - mature virions with or without envelope
euryxen
Complex symmetry
Replicate in cytoplasm
Stable in the environment
Skin lesions a prominent feature
Individual poxviruses tend to infect particular host
species; some poxviruses are not species-specific
airborne, arthropod, contact transmission, per cut
- largest virus of animals
Asfarviridae Key Points
Enveloped DNA virus Icosahedral symmetry Replicates in cytoplasm of host cells and in soft ticks of the Ornithodorus species Causes African swine fever
Reoviridae Key Points
Non-enveloped viruses with double or triple layered
capsid and icosahedral structure
Segmented double-stranded RNA
Replicate in cytoplasm
Three genera of veterinary importance
Orthoreovirus, Orbivirus, Rotavirus:
-0rthoreoviruses cause arthritis and tenosynovitis
in poultry
-Rotaviruses cause enteritis in neonatal farm
animals
-0rbiviruses are arthropod-borne infections that
cause African horse sickness in horses
and bluetongue in sheep and in other domestic
and wild ruminants
Birnaviridae Key Points
Key points
Double-stranded RNA viruses with icosahedral
symmetry
Replicate in cytoplasm
Stable in the environment
I The family is composed of three genera:
-Avibirnavirus contains viruses which cause
infectious bursal disease
-Aquabirnavirus contains viruses which cause
infectious pancreatic necrosis in salmonids
-Entomobirnavirus contains viruses which infect Insects
Paramyxoviridae Key Points
Large pleomorphic enveloped viruses
Negative sense single-stranded RNA
Helically symmetrical nucleocapsid
Replicate in the cytoplasm
Subfamilies Paramyxovirinae and Pneumovirinae
divided into five genera, each containing viruses of veterinary importance
Cause rinderpest, peste des petits ruminants, canine
distemper, Newcastle disease and a range of
respiratory diseases in domestic animals
Rhabdoviridae Key Points
Enveloped RNA viruses with helical symmetry and rod-shaped morphology Rabies virus and related lyssaviruses
-present in saliva; transmitted by biting carnivores and bats
–cause encephalitis in mammals which is invariably
. fatal Vesicular stomatitis viruses
-transmitted by direct contact and environmental
contamination or by arthropod vectors
–cause febrile disease with vesicular lesions
. especially in cattle, horses and pigs Bovine ephemeral fever virus
-transmitted by biting arthropods
–causes febrile transient illness with ill-defined
clinical signs
Bornaviridae Key points
Labile, enveloped virus with a particular affinity
for nervous tissues
Genome consists of negative-sense,
single-stranded RNA
Replicates in nuclei of neural cells
The single genus Bornavirus contains one species
Causes Borna disease, an infection of the CNS,
fatal in many domestic species, particularly horses
Bunyaviridae
Medium-sized, enveloped, single-stranded RNA
viruses
Replicate in the cytoplasm
Labile in the environment
More than 300 viruses in the family, the majority
are arthropod-borne
The family is composed of five genera:
-Bunyavirus contains viruses which cause congenital
defects in cattle and sheep
-Phlebovirus contains the virus which causes Rift
Valley fever
-Nairovirus contains the virus which causes Nairobi
sheep disease
–Hantavirus contains many viruses which cause
haemorrhagic fever in humans; rodents act as
reservoirs
-Tospovirus contains viruses of plants
Picornaviridae
Non-enveloped, positive-sense, single-stranded RNA viruses with icosahedral symmetry
Replicate in cytoplasm
Resistant to many organic solvents;
individual members differ in their susceptibility to pH change
Four genera, Aphthovirus, Enterovirus, Cardiovirus and Hepatovirus contain viruses of veterinary
significance
Aphthoviruses cause foot-and-mouth disease
Enteroviruses cause swine vesicular disease,
Tescheflalfan disease, reproductive problems and enteritis in pigs
Cardioviruses cause encephalomyocarditis in young pigs
Hepatoviruses cause encephalomyelitis in chickens
Coronavirus Key points
Enveloped, pleomorphic, single-stranded RNA viruses Replicate in the cytoplasm -~abilien the environment Two genera: -Coronavirus, helical nucleocapsid -Torovirus, tubular nucleocapsid Coronaviruses: -Systemic disease in cats -Enteric and systemic disease in pigs -Respiratory disease in poultry -Enteric disease in cattle
Flaviviridae
. Enveloped labile viruses Positive-sense, single-stranded RNA
Replicate in the cytoplasm
Tho genera of veterinary importance, Flavivirus and
Pestivirus
Most viruses in the genus Flavivirus are transmitted
. by arthropods and cause encephalitis Pestiviruses, which are transmitted directly or indirectly,
cause bovine viral diarrhoea, border disease and
classical swine fever
Prions - Key points
Key points
Prions are proteinaceous particles apparently devoid
of nucleic acid
Aetiologically implicated in the transmissible
spongiform encephalopathies, fatal neurodegenerative
diseases with long incubation periods
Neuropathological changes, which include vacuolation
of both neurons and neuropil without evidence of an
inflammatory response, are associated with the
accumulation of abnormally-folded
host-derived prion protein
Transmissible spongiform encephalopathies include:
Scrapie in sheep
-Bovine spongiform encephalopathy
-Feline spongiform encephalopathy
-Transmissible mink encephalopathy
Herpesviridae
Enveloped DNAviruses with icosahedral symmetry
m Replicate in the nucleus
Labile in the environment
Three subfamilies of veterinary importance:
Alphaherpesvirinae, Betaherpesvirinae,
Gammaherpesvirinae
m Cause diseases of the respiratory, reproductive and
nervous systems; may cause cell transformation in
some species
m Latency is a common outcome of infection with
these viruses
