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