Author, Donkey, Bureaucrats, Administrators
53,803
edits
Changes
Jump to navigation
Jump to search
no edit summary
#REDIRECT [[Bovine Virus Diarrhoea]]
{{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]]