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| − | {{unfinished}}
| + | #REDIRECT[[Bovine Viral Diarrhoea Virus]] |
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| − | {{toplink
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| − | |linkpage =Viruses
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| − | |linktext =VIRUSES
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| − | |sublink1=Flaviviridae
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| − | |subtext1=FLAVIVIRIDAE
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| − | |pagetype =Bugs
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| − | }}
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| − | <br>
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| − | ====Antigenicity====
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| − | *RNA virus closely related to [[Classical Swine Fever]] and [[Border Disease Virus]]
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| − | *2 Serological Types
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| − | **BVDV-1 is traditional, existing as two biotypes
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| − | ***BVDV-1nc: noncytopathogenic
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| − | ***BVDV-1c: cytopathogenic
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| − | **BVDV-2 is an emerging hemorrhagic virus
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| − | ====Hosts====
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| − | *Cattle
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| − | ====Pathogenesis====
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| − | [[Image:BVD-MD.gif|right|thumb|125px|<small><center>Small erosions of MDV/BVDV - vesicles are microscopic (Courtesy of Alun Williams (RVC))</center></small>]]
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| − | [[Image:Bvd2.gif|right|thumb|125px|<small><center>Coalescing lesions of BVDV (Courtesy of Alun Williams (RVC))</center></small>]]
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| − | '''BVDV-1c'''
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| − | *Infects cattle regardless of age
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| − | *Usually mild: diarrhoea with recovery in 10 dyas
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| − | *Immunosuppression can lead to secondary infection
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| − | '''BVDV-2nc'''
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| − | *Transient '''thrombocytopenia''' and '''leukopenia''' over 2 weeks
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| − | *Hemorrhages
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| − | *Secondary infection
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| − | *Death
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| − | '''BVDV-1nc'''
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| − | *'''Transplacental''' infection of naive heifers
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| − | *Outcome depends on age of fetus at contraction
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| − | **0-110 days: '''abortion''' or '''persistently infected (PI)''' calves born
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| − | **110-220 days: congenital damage with noticeable '''CNS''' and '''musculoskeletal''' lesions
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| − | **220 days to term: '''active immunity''' developed
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| − | '''Mucosal Disease'''
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| − | *Mucosal disease is caused by a '''superinfection''' of PI animals with a second homologous cytopathic biotype (eg BVDV-1nc followed by BVDV-1c)
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| − | *Infection typically occurs between '''6-18 months of age''' but is variable
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| − | *Superinfection will quickly '''spread horizontally''' among PI animals
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| − | *Invariable '''fatal'''
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| − | *Characterized by [[Cavity & Gingiva - Pathology#Bovine Viral Diarrhoea / Mucosal Disease|'''oral]] and enteric erosions''', particularly overlying Peyer's patches, and ulceration of the feet
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| − | *Animals can show anorexia, depression and/or diarrhoea for 2-5 days before death
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| − | *Vaccination can lead to '''iatrogenic''' infection in undiagnosed PI calves
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| − | ====Epidemiology====
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| − | *A major concern is that it can be confused with [[Foot and Mouth Disease (FMDV)|FMD]] (especially as it often occurs with clinical signs of salivation and depression)
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| − | *Virus is widespread: 60-70% exposure by 4 years of age
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| − | **Often may sweep through a whole colony of young stock causing profuse diarrhoea (perhaps febrile) for a few days and then recover
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| − | **Due to primary exposure to cytopathic strain of virus
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| − | *PI cows:
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| − | **100% vertical transmission to offspring
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| − | **Are infected with BVDV-1nc and NEVER BVDV-1c
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| − | **Are often antibody-negative (though they can show low levels of Ab to ''heterologous'' virus)
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| − | **Show a wide range of clinical signs:
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| − | ***Severe congenital damage (ataxia)
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| − | ***Poor body condition
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| − | ***Increased susceptibility to enteric and respiratory disease
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| − | **Act as the herd '''reservoir''' of BVDV
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| − | **Can ONLY be identified by blood testing
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| − | *Transfer via '''semen''', '''direct contact''' with acutely infected animals, or vertical from dam to offspring
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| − | *Transfer can be iatrogenic: repeated use of needles and gloves, etc.
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| − | ====Diagnosis====
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| − | *Traditional test: virus isolation followed by serology on infected cells
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| − | *'''ELISA''' for virus '''antigen''' in animals with persistent viremia (will show up 3-8 days post-infection)
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| − | *PI calves often appear virus negative as a result of receiving neutralizing Ab in colostrum: can be countered by RT-PCR
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| − | *'''Paired serum samples''' from cows with acute BVDV
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| − | *'''Herd sampling''' by ELISA for antibody on bulk milk
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| − | ====Control====
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| − | *No known treatment to reverse persistent infection or to cure mucosal disease
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| − | *BUT, without exposure to BVDV, the whole herd is at risk as there is no developed immunity
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| − | *'''Vaccination of dams''' before pregnancy will prevent PI calves being born
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| − | **'''Beta-propiolactone inactivated''' vaccine
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| − | **Combine with screening for antigen and removal of PI animals
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