| Line 1: |
Line 1: |
| − | {{unfinished}}
| + | #REDIRECT[[Bovine Viral Diarrhoea Virus]] |
| − | | |
| − | {{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
| |