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Bovine Viral Diarrhoea Virus (view source)

Revision as of 18:28, 23 August 2010

362 bytes removed ,  18:28, 23 August 2010
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==Transmission and Epidemiology==
 
==Transmission and Epidemiology==
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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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==Pathogenesis==
 
==Pathogenesis==
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===Laboratory Tests===
 
===Laboratory Tests===
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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
    
===Pathology===
 
===Pathology===
 
[[Image:BVD-MD.gif|right|thumb|125px|<small><center>Small erosions of MDV/BVDV - vesicles are microscopic (Courtesy of Alun Williams (RVC))</center></small>]]
 
[[Image:BVD-MD.gif|right|thumb|125px|<small><center>Small erosions of MDV/BVDV - vesicles are microscopic (Courtesy of Alun Williams (RVC))</center></small>]]
 
[[Image:Bvd2.gif|right|thumb|125px|<small><center>Coalescing lesions of BVDV (Courtesy of Alun Williams (RVC))</center></small>]]
 
[[Image:Bvd2.gif|right|thumb|125px|<small><center>Coalescing lesions of BVDV (Courtesy of Alun Williams (RVC))</center></small>]]
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==Treatment and Control==
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==Links==
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==References==
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====Pathology====
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*'''Mucosal Disease''': erosive condition produces small multiple, cleanly punched out lesion in mouth
 
*'''Mucosal Disease''': erosive condition produces small multiple, cleanly punched out lesion in mouth
 
*[[Neutrophils|Neutrophils]] invade the ulcer and if bacterial colonisation occurs, further excavation follows. Either:
 
*[[Neutrophils|Neutrophils]] invade the ulcer and if bacterial colonisation occurs, further excavation follows. Either:
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*Lesions extend throughout gut with particularly big ulcers in small intestine over [[Peyer's Patches - Anatomy & Physiology|Peyers patches]]. Necrosis occurs in lymph nodes and [[Spleen - Anatomy & Physiology|spleen]]
 
*Lesions extend throughout gut with particularly big ulcers in small intestine over [[Peyer's Patches - Anatomy & Physiology|Peyers patches]]. Necrosis occurs in lymph nodes and [[Spleen - Anatomy & Physiology|spleen]]
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====<span id="BVDHistology">Histology</span>====
   
*No vesicular stage, prickle cells die off from surface resulting in layer of necrotic debris over epithelial layer
 
*No vesicular stage, prickle cells die off from surface resulting in layer of necrotic debris over epithelial layer
 
*Infection penetrates inward through stratum germinativum.
 
*Infection penetrates inward through stratum germinativum.
 
*Epithelium does not recover as animal does not recover
 
*Epithelium does not recover as animal does not recover
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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)
  −
*Virus is widespread: 60-70% exposure by 4 years of age
  −
**Often may sweep through a whole colony of young stock causing profuse diarrhoea (perhaps febrile) for a few days and then recover
  −
**Due to primary exposure to cytopathic strain of virus
  −
*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====
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==Treatment and Control==
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*Traditional test: virus isolation followed by serology on infected cells
  −
*'''ELISA''' for virus '''antigen''' in animals with persistent viremia (will show up 3-8 days post-infection)
  −
*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
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====Control====
   
*No known treatment to reverse persistent infection or to cure mucosal disease
 
*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
 
*BUT, without exposure to BVDV, the whole herd is at risk as there is no developed immunity
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**Combine with screening for antigen and removal of PI animals
 
**Combine with screening for antigen and removal of PI animals
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==Links==
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==References==
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<br>A pestivirus which may result in abortion of fresh, autolysed or mummified foetuses.
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Calves may also be born alive and may be weak, uncoordinated due to cerebellar hypoplasia (cerebellar hypoplasia also seen with feline panleukopenia infection).
       
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