Arteriviruses
Ateriviridae
Genome
Virion
Enveloped
Replication
Target
Fragility
Features
Monopartite, linear, (+)ssRNA
Isometric core of 20 – 30 nm
surrounded by lipid-containing
envelope
Yes
Cytoplasmic
Primarily lung macrophages
Fragile
Species of note (2)
1. Equine viral arteritis (EVA)
- Causes generalised vasculitis resulting in
è oedema / haemorrhage / abortion
- Usually subclinical BUT clinical disease characterised:
o Pyrexia (1-5days)
o Rhinits, conjunctivitis w/
nasal & ocular discharge
o Subcut oedema of
o Photophobia
limbs, ventral ab.
o Skin rash, anorexia
o Depression / dyspnoea /
diarrhoea
- Transmission
o Respiratory / venereal / congenital / indirect
** virus present in semen, resp secretions / urine / faeces /
aborted foetuses
o Carrier stallions = viral reservoir
- Diagnosis:
o blood without anti-coagulant, Nasal and
conjunctival swabs, semen for serology, virus
isolation and identification by qRT-PCR.
o Endemic in all continents except Aus. & Antarctica
2. Porcine reproductive & respiratory syndrome
virus (PRRSV)
Two major genetic lineages:
i)
PRRSV type 1 à European
ii)
PRRSV type 1 à north American
- Transmission
o Pig – pig via direct contact w/ sick animals,
contaminated objects or infected meat
o Virus shed @ saliva, nasal secretions, urine,
semen
o Vertical transmission => foetal death / weak piglets
- Tropism for macrophages
o Compromises cellular immune response and
damages mucosal surfaces
Coronaviridae
Genome
Virion
Enveloped
Replication
Target
Fragility
Features
Monopartite, linear, (+)ssRNA
Spherical
Yes
Cytoplasmic
Epithelial cells of resp. & GIT
Neuro. Tissues
Fragile in enviro.
2. Porcine epidemic diarrhoea virus (PEDV)
- Present in Europe & asia
- Very similar to TGEV à can’t distinguish by clinical
signs
o BUT, no cross protection
3. Feline coronavirus (Feline infectious peritonitis
FIPV)
2 pathotypes
i)
Feline enteric coronavirus (FECV)
o Ubiquitous enteric biotype
ii)
Feline infectious peritonitis virus (FIPV)
o Virulent biotype, causes FIP in individual cat
@ replication in cat intestinal tract
- FCoV mutates frequently, esp. in kittens
è sporadic critical mutations
è enable FCoV to infect & replicate in macrophages
1. Transmissible gastroenteritis virus (TGEV)
- Replicates in epithelial cells of SI
o @ neonates/young à infection of SI AND patchy
atrophy of intestinal villi
- PRRSV is deletion mutant derived from TGEV
o Deletion of S-gene
o Loss of tropism for enterocytes, but increased
tropism for lungs
- Symptoms:
o Profuse diarrhoea / freq. vomiting / rapid
dehydration / shivering / thirst
§ Piglets die w/in 1 – 2 days
- FIPV infects macrophages/monocyte cells
Macrophages then replicate the mutated coronavirus
carry it to target tissues such as the peritoneum, pleura,
kidney, uvea, and nervous system, resulting in widespread
immune-mediated vasculitis, disseminated perivascular
pyogranulomatous inflammation, and exudative fibrinous
polyserositis
à characteristic lesions of FIP
** effective treatment & reliable vaccine lacking
à deadliest infectious disease of cats
Clinical signs:
- Varied, Ocular, neuro signs are common
4. Bovine Coronavirus
- Infects resp. and GIT cells
ð Severe diarrhoea in newborn calves
o SI & LI cells à maldigestion & malabsorption
ð Winter dysentery in adult cattle
o Acute onset diarrhoea
o Fall in milk production
ð Resp tract infections in calves & feedlot cattle
o Epithelial cells of nasal cavity & trachea
-
Reoviridae
Genome
Virion
Enveloped
Replication
Target
Fragility
Features
Segmented linear dsRNA
10-12 segments
Icosahedral w/ double capsid
No
Cytoplasmic
Mucosal gut cells
Stable
5. Infectious bronchitis virus
Highly contagious viral disease of chickens
Many serotypes – via antigenic drift
Transmission
o Resp route
Infects respiratory epithelium +/- kidney, gonads, GIT
Symptoms:
o URT disease signs
o Other: egg drop / depression / increased H2O
intake
large poultry producers vaccinate
GENUS: Orbivirus
i)
African horse sickness virus (AHSV)
- Insect-borne disease
- Causes serous effusion and haemorrhage in organs
and tissues
- Cardiac form:
o Subacute, incubation 1 – 2 wks
o Fever <1wk, then edema of supraorbital
foassae
- Acute resp. form:
o Dyspnoea / coughing / frothy nasal discharge
(end stage)
ii)
Bluetongue virus (BTV) à lecture 13
iii) Epizootic haemorrhagic disease virus (EHDV)
- Spread by culicoides midges
- May cause symptoms similar to BTW
o Degenerative changes and focal haemorrhage in
the oesophagus, larynx, tongue, and skeletal
muscles
Rotaviruses
- Exist in almost all animal species
- Transmission = faecal – oral
- Infects tips of villi in SI
- Target: young animals
-
1. Equine rotavirus
Cause acute enteritis assoc. w/ diarrhoea in neonates
Faecal – oral transmission
Destroys enterocytes @ tip of villi in SI
Symptoms:
o Fever, depression, foul-smelling diarrhoea
2. Bovine rotavirus
- In <2wks old, produces high morbidity outbreaks of
diarrhoea
- Pathogenesis similar to equine rotavirus
o Pale yellow diarrhoea
§ w/ mucous & blood flecks
- secondary infection can occur
iv) Warrego virus & Wallal virus
- Known as Kangaroo blindness viruses
- Spread by culicoides species
- Virus has predilection for retinal cells
o Severe panuveitis & retinitis