Difference between revisions of "Bovine Virus Diarrhoea"

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(Redirected page to Bovine Viral Diarrhoea Virus)
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#REDIRECT[[Bovine Viral Diarrhoea Virus]]
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{{unfinished}}
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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====
 +
*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
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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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'''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
 +
*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
 +
*Vaccination can lead to '''iatrogenic''' infection in undiagnosed PI calves
 +
 
 +
====Epidemiology====
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*Virus is widespread: 60-70% exposure by 4 years of age
 +
*PI cows:
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**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

Revision as of 21:33, 21 October 2008


 This article is still under construction.


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VIRUSES
FLAVIVIRIDAE



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
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