A detailed overview of Module 2 Virology-Arboviruses
Does not include retroviruses, lentiviruses, TSE's, caliciviruses, bornaviruses, papillomaviruses and polyomaviruses.
Arthropod borne, RNA.
Dist. on temperature.
Enzootic and Epizootic cycles.
Epizootic comes from changes in climate, ecology and from long distance movement.
DIAGNOSE:Serology
Exotic to NZ
Reoviridae
Nota:
Tough in environment.
Orbiviruses
Nota:
Replicate in LN and then to blood.
They like the endothelial cells which causes vascular permeability, occlusion and oedema.
Many serotypes each (makes vaccination hard).
Blue tongue
Culicoides midge in AUS. Confined to North
AUS. Could come to NZ by importing
ruminants into zoos
Signs=Swollen mouth, droopy ears,
coronary band swelling, lameness.
African Horse Sickness
Highly fatal disease of horses and mules.
Serotypes 1-8 (out of 9) are pathogenic.
Control=Vaccination (poly or
monovalent), vector control, killing
infected horses,.
Rotaviruses
Nota:
Common cause of diarrhoea in infants - Disease seen in young animals 1-8 weeks old.
Acid stable virus, hardy in environment.
Factors contributing=chilling, overcrowding, poor hygiene, no colostrum.
Diagnose with agglutination test.
Control with vaccine.
Bunyaviridae
Nota:
Can cause disease in humans.
Can be transmitted via arthropod eggs too.
Rift valley fever
Not a huge threat to coming
into NZ
Culex and aedes mosquitos
Akabane
Exotic to NZ- we don't have Culicoides
Causes reproductive issues in
when it switched to epizootic
cycle, no clinical signs in enzootic
cycle.
Nairobi sheep disease
Not in NZ
Causes fever, haemorrhagic
enteritis, abortion and mortality.
Diagnose by virus isolation,
control by vaccine or tick
control
Togaviridae
Alphaviruses
Nota:
Fragile RNA virus
Encephalitis
Nota:
Primary and secondary viraemia occurs, primary in LN and secondary in organs. It is infective to the arthropod at the level of secondary viraemia, and it then invades the CNS.
Depression, incoordination, droopy face, impaired vision, circling, paralysis.
You can vaccinate (also works to control human infection)
Eastern equine encephalitis
Western equine encephalitis
Venezuelan equine encephalitis
Nota:
Abortion in humans
Flaviviridae
Nota:
Easy to kill, Nucleic acid itself is infectious.
Dengue
Nota:
Immunity for life for a single serotype only (no cross protection)
West Nile Virus
Nota:
Uses humans and some mammals as secondary hosts
Of Veterinary Importance
Louping ill
Nota:
Exotic to NZ
Neurological signs.
Control by vaccines and acaricides
Wellesbron disease
Japanese Encephalitis
Nota:
Exotic to NZ
Pigs are amplifier host (can get sick too though).
Vaccine available.
BVD and MD
Outcome dependent on age,
immunity, dose, strain and
pregnancy status
BVD: Clinical infection is common in
animals 6-18 months old, fever
diarrhoea etc. High morbidity, low
mortality.
If pregnant: Under 40days=Failure to
conceive, 40-120 days=Persistently
infected calf, 120-150
days=congenital defects.
Can vaccinate to control
more persistently infected
animals being born.
MD: Low morbidity, high
mortality. Acute=Fever, erosions
etc leading to death.
Chronic=Erosions on muzzle,
death in 2-6 months.
The BVD strain is either inherited
or becomes cytopathic in
persistently infected animals. They then shed the disease.
Diagnosis is by normal
means, but PI animals are not
antibody positive.
Prevention by vaccination.
Classical swine fever
Nota:
Exotic to NZ
Haemorrhage, ulcers, petechiae.
Equine infectious Anaemia
Of the lentivirus family but is an arbovirus too.
1-3 week incubation followed by either acute or
subacute forms of disease. Acute has serious effects
followed by 80% mortality. Subacute has lifelong
infection and shedding with recurrent episodes.