Difference between revisions of "Bovine Virus Diarrhoea"

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#REDIRECT[[Bovine Viral Diarrhoea Virus]]
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{{unfinished}}
 +
 
 +
====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====
 +
[[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>]]
 +
'''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 [[Cavity & Gingiva - Pathology#Bovine Viral Diarrhoea / Mucosal Disease|'''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
 +
 
 +
====Pathology====
 +
 
 +
*'''Mucosal Disease''': erosive condition produces small multiple, cleanly punched out lesion in mouth
 +
*[[Neutrophils - WikiBlood|Neutrophils]] invade the ulcer and if bacterial colonisation occurs, further excavation follows. Either:
 +
::#This lesion develops a granular base and becomes diphtheritic.
 +
::#If bacterial colonisation does not take place, healing occurs within fourteen days.
 +
*Seen in most parts of mouth (or maybe on muzzle) e.g. dental pad, [[Cheeks - Anatomy & Physiology|cheeks]], sides of [[Oral Cavity - Tongue - Anatomy & Physiology|tongue]]
 +
*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]]
 +
 
 +
====<span id="BVDHistology">Histology</span>====
 +
*No vesicular stage, prickle cells die off from surface resulting in layer of necrotic debris over epithelial layer
 +
*Infection penetrates inward through stratum germinativum.
 +
*Epithelium does not recover as animal does not recover
 +
====Epidemiology====
 +
*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====
 +
*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
 +
 
 +
====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
 +
[[Category:Pestiviruses]][[Category:Cattle]]
 +
[[Category:Oral_Cavity_-_Erosive_&_Ulcerative_Pathology]]

Revision as of 14:00, 24 May 2010


 This article is still under construction.


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

Small erosions of MDV/BVDV - vesicles are microscopic (Courtesy of Alun Williams (RVC))
Coalescing lesions of BVDV (Courtesy of Alun Williams (RVC))

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

Pathology

  • Mucosal Disease: erosive condition produces small multiple, cleanly punched out lesion in mouth
  • Neutrophils invade the ulcer and if bacterial colonisation occurs, further excavation follows. Either:
  1. This lesion develops a granular base and becomes diphtheritic.
  2. If bacterial colonisation does not take place, healing occurs within fourteen days.
  • Seen in most parts of mouth (or maybe on muzzle) e.g. dental pad, cheeks, sides of tongue
  • Lesions extend throughout gut with particularly big ulcers in small intestine over Peyers patches. Necrosis occurs in lymph nodes and spleen

Histology

  • No vesicular stage, prickle cells die off from surface resulting in layer of necrotic debris over epithelial layer
  • Infection penetrates inward through stratum germinativum.
  • Epithelium does not recover as animal does not recover

Epidemiology

  • A major concern is that it can be confused with 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

  • 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

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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