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BVD Flashcards

1
Q

how is BVD transmitted?

A 
direct via nasal secretion
semen
urine
milk
saliva
tears
foetal fluid
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2
Q

what is the main source of virus for BVD?

A

PI = persistently infected

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3
Q

what determines what happens after infection?

A

immune status

preg status

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4
Q

what does the antigen indicate?

A

virus (active infection)

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5
Q

what does the antibody indicate?

A

exposure/immunity to virus

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6
Q

what happens when cow infected but NOT pregnant?

A

if immune & not preg = nothing (or v mild TI)

if not immune & not preg = TI (transient)

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7
Q

what is TI?

A

rarely noticed
viraemia 3-14d only = antigen + (nasal shedding)
but immune response from d14 = recovery: Ab
Ag -ve but ab +ve

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8
Q

what happens when infected & pregnant? (if immune)

A

nothing
Ab clear virus
foetus unaffected

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9
Q

what happens when infected & preg (NOT immune)?

A

cow - TI & ab BUT bad news for foetus
if 1st trimester = PI, abort (0-120d)
if 2nd trimester = congenital defects, abort (120-240d)
if 3rd trimester = stillborn, stunted, abort (240-280d)

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10
Q

how do PIs come about?

A
  1. foetus infected in 1st trimester of preg:
    - before immunocompetent
    - BVDV seen as ‘self’
    - foetus/calf NEVER fights the virus (no Ab)
  2. offspring of PI
    - PI cow will alw produce PI calf (BVD gets into oocyst)

Ag +ve, ab -ve (if MDA used up) FOREVER!
massive source of virus on farm

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11
Q

CS of TI?

A 
often v little, all temp
? pyrexia
? D+ 
? anorexia
? infertility
? immunosuppression 
Ab peak @ 12wks after infection & remain for years (?lifelong)
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12
Q

is PI for life?

A

yes!!

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13
Q

impacts of PI?

A 
stunted, poor doing
poor DLWG
prone to 2dary infections: scour, pneumonia - can be underlying BVD prob 
90% under 2yo, most die
never make Ab
develop mucosa dx
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14
Q

how does mucosal dx occur in PIs?

A

mutation of own virus from NCP to CP/superinfection w w CP from another PI in pen
CP virus can circulate causing an outbreak of mucosal dx w/i PIs

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15
Q

CS of mucosal dx?

A 
ulceration of ALL mucosa
salivation
haemorrhagic D+ 
6mth-2y 
EUTH asap
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16
Q

ddx of oral ulceration?

A 
FMD
bluetongue
BVD/mucosal dx 
malignant catarrhal fever
calf diphtheria
actinobacillosis - wooden tongue
actinomycosis - lumpy jaw
trauma
(IBR)
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17
Q

which out of the ddx of oral ulceration is notifiable?

A

FMD

bluetongue

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18
Q

what are the effects of TI in bulls?

A

sperm motility & morphology affected temp
2 wks viraemia + 9wks spermatogenesis of new sperms
virus also sheds in semen (? up to 5mth i.e. longer than nasal secretions) - may be viable KIV

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19
Q

what are the effects of PI in bulls?

A

secrete virus in semen continually - sperm Q reduced

foetus may/may not be PI

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20
Q

what is a cumulus?

A

infection during puberty
Ag -ve, Ab +ve but Ag being produced in testes
v unusual

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21
Q

how long should farmers wait to use bulls after purchase?

A

2 months: can be TI despite -ve Ag test

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22
Q

how is the herd affected by BVD?

A 
if immune (+ not massive viral load) = v little
if herd not immune (naive & not vax) = abortion, still birth, congenital prob, D+, infertility, (immunosuppression), poor growth rates, decreased semen Q, mucosal dx cases, increase dx in gen.
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23
Q

what family is the BVDV from?

A

flaviviridae

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24
Q

what genus is BVDV?

A

pestivirus

25
what genotypes of BVDV are there?
``` 2 genotypes BVD1 = classic, UK BVD2 = more severe TI some vax only license for 1 genotype prone ot mutations = strain variation ```
26
what biotypes of BVDV are there?
2 biotypes of each genotype NCP = TI CP = superinfect PIs to cause mucosal dx - kills cells; mutation of NCP
27
which gene mutation results in NCP to CP?
NS2/3 mutation
28
what makes BVDV an effective virus?
``` multiplies in multiply cells w/o killing them (NCP) crossing placenta (PI & cong dx) causes inflammation of ovary & lowers LH (infertility) interrupts GI neurones (D+) causes immunosuppression -hides from immune resp -down regulates interferon -decrease leucocyte no. (lymphopenia) -effects on B & T cell resp ```
29
PI cow will ALWAYS give birth to PI calf: T/F?
true
30
PI calf MIGHT have PI mother (or mother had TI when preg): T/F
true
31
what are Ab results affected by?
MDA lasts 9mths (less in PI) | vax
32
how to test if animal is PI?
test for antigen (blood, tissues, milk) - PCR/Ag ELISA PI result = Ag +ve, BUT can be TI > retest in 3wks i.e. if TI, will clear virus & mount immune resp 3 wks later: -result PI = Ag +ve (Ab +/-) -result TI = Ag -ve (Ab +)
33
how to test if animal has been exposed?
``` test blood/milk for Ab -ve = not exposed BUT is it PI? -might want to test Ag to check +ve = exposed/vax but...when? calf - complicated bcs MDA not done for single animal ```
34
how long does MDA last for?
9 months
35
how does MDA affect testing results?
``` Ag testing: -MDA can neutralise Ag in PI = false -ve -PI missed -don't use blood if <30d -tissue ok from birth Ab testing: -false +ve if test calves <9mths ```
36
what is the diagnostic gap?
MDA might give false -ve for tissue Ag MDA effect in PI peaks @ 3wks 'tag test early/test late'
37
how to check if live calf exposed in utero?
1st check for Ag (foetal fluid/tissue) to see if PI -if +ve & calf alive, retest in 3wks: if Ag +ve = PI, if Ag -ve = not PI but was it exposed in utero? if not exposed in utero = Ab -ve if exposed in utero (after 120d) = Ab +ve bcs immune system of foetus can produce Ab BUT need pre-colostral sample to avoid MDA from colostrum ?practical if Ab -ve (& Ag -ve) = calf not exposed in utero (rare to get this result due to vax/exp of mom)
38
how to check if pregnant cow carrying PI in utero?
Ag (mom) +ve = could be PI mom, retest; if -ve = TI so maybe PI in utero Ag -ve = not currently viraemic (could've previous TI) Ab +ve = exposed/vax but dk when Ab -ve = not exposed so in-utero infection unlikely (could also be PI)
39
how to test if herd has been exposed to BVD?
screen test: 5 calves 9-18mths in each management group test for Ab i.e. exp tells you if GROUP exposed/immune to BVD (not what calf is PI) if +ve need to hunt for PI
40
how does screen testing work?
PI secretes massive amt of virus nose to nose contact allows spread those in contact = TI, become Ab +ve in 3 wks (if happened to sample PI it would be Ab -ve while the rest +ve) £
41
what is a management group?
nose to nose contact tgt for 2+ months not as effective @ grass
42
if screen test results come back as all Ab -ve what does that mean?
no evidence of active BVD | monitor
43
if screen test come back as occasional +ve, 'not -ve'
``` active BVD infection can't be ruled out sample more from group re-test if single +ve check age check if vax hunt PI ```
44
if screen test multiple +ves
active/recent BVD | hunt PI
45
what are the problems w screen test?
relies on farmer's honesty re. management groups need accurate DOB for MDA vax interferes need distinct calf grps if +ve - may have been PI on farm for 9mths already causing prbs -defo other PI in utero (in mothers) that can't be prevented
46
what is the scottish gov BVD scheme for dairy cows?
screen test 10 calves q6mths bcs no distinct management groups
47
how much of herd needs to be sero+ve for BT +ve?
5% herd | bulk milk Ab not that useful
48
is bulk milk Ab useful?
not that useful (removed from scottish gov scheme) | lag btwn infection & +BMT (up to 36 mths)
49
how to hunt for PI?
test whole herd for Ag - next step following +ve screen test -tissue, blood, milk (indiv/bulk but NOT beef) £££ but tells if there's any PI make sure you have test result for every animal (bulls, in calf heifers) BUT what if PI has been sold/died?
50
how to prevent sampling all cows for PI?
'presumed -ve status' but need to make sure a calf for every cow can 'pool' blood samples (not <6wks old) -if have +ve in batch, have to sample indiv -pool all heathy animals tgt & any animals that sus, test separately bulk milk can detect 1xPI in 300 cows
51
how much does BVD Ab ELISA (blood) cost?
£4.10
52
BVD Ab ELISA (milk) cost?
£5.35
53
BVD Ag ELISA (blood) cost? BVD PCR blood (Ag) cost? BVD PCR BMT (Ag) cost? BVD PCR tissue (Ag) cost?
5. 80 4. 45 28. 45 3. 70
54
how long must we test for before considering stopping Ag testing?
have at least 12mth of no PIs born before can consider stopping Ag testing make sure ALL animals tested for Ag
55
risks for BVD?
``` bought in animals* rented grazing away from farm* heifer rearing away from farm* showing/bringing home from market* contact w neighbours stock (double fence!) people: vet/staff/foot trimmers/AI tech equipm vehicles: milk tanker/feed deliveries ``` *esp impt if preg animals!
56
control measures for open herds?
``` test bought in animals for Ag buy 'accredited free' animals isolate 4 wks avoid buying in calf animals (can't test unborn calf) trojan cow! carrying PI: high Ab ```
57
controls for BVD?
vax - complete 1ary course before insemination not 100% effective when have massive challenge often incorrectly admin on farm vax Ab complicates testing
58
what vax are there for BVD?
bovela (£4.95/dose) modified live, BVD 1&2, single dose from 3mth, 3wks prior to service, not bulls yearly booster bovillis BVD (£2.47/dose) inactivated BVD 1, 2 doses from 8 mth, 4wks prior to service initial 6mth booster then 12mthly can combine w IBR marker live
59
what accreditation scheme is there?
CHeCS = regulatory body for cattle health scheme

mod 21 (12 decks)

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