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VETM 422: Virology > bovine viral diseases 1 - Steph > Flashcards

bovine viral diseases 1 - Steph Flashcards

1
Q

BVDV stands for

A

bovine viral diarrhea virus

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2
Q

most common BVDV strains

A

BVDV1 and BVDV2

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3
Q

which subtypes of BVDV are most common

A

Type 1a and 1b and 2a and 2b

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4
Q

what is the most prevalent strain in cattle

A

Type 1b - likely because most vaccines have types 1a & 2a

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5
Q

what is the most important gene in BVDV for mucosal disease?

A

NS2 and NS3

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6
Q

BVDV host range

A

cattle, cervids, rabbits, sheep, goats, camelids, moose, goats, pigs, java mouse deer

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7
Q

To be a potential wildlife reservoir for BVDV, the animal species must (4 requirements)

A

1) be susceptible to BVDV
2) shed BVDV
3) maintain BVDV in the population AND
4) have sufficient contact with cattle that allow spillback infections

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8
Q

can pigs get BVDV

A

yes by getting fed raw milk or presence of cows & sheep

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9
Q

pigs BVDV clinical signs

A

poor conception rates, abortion, and stillborn piglets but can also appear without clinical signs

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10
Q

pig prevalence BVDV

A

2-43% in NA herds - so we do not know

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11
Q

BVDV clinical signs in lambs

A

lambs do a lot of shaking - called hairy shakers

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12
Q

BVDV clinical signs

A

not eating, diarrhea

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13
Q

BVDV infection month 1 of gestation consequences

A

early embryonic death & return to estrus

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14
Q

BVDV infection month 2-4 of gestation consequences

A

persistently infected - antibody negative OR abortion/malformation

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15
Q

Why does BVDV cause persistent infection if dam infected at 2-4 months gestation?

A

At around 4 months/120 days, the fetus decides what is self/non-self. Because the infection takes place BEFORE this distinction, the virus is considered part of self. ONLY virus that does this

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16
Q

how does BVDV target different organs for malformation?

A

BVDV targets cells multiplying quickly - whichever organ is growing quickly at the time of infection is the one that gets malformed

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17
Q

BVDV infection month 5-9 of gestation consequences

A

normal animal - antibody positive OR cause abortion/malformation

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18
Q

where can you find BVDV (pathogenesis)

A

Oronasal infection, tonsils - lymphatic spread, regional lymph nodes - blood circulation - lymphoid tissue of GI and lungs, thymus/bone marrow/spleen, and all other organs depending on virulence of virus

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19
Q

in persistent infections (PI) where do you find BVDV

A

ALL organs are BVDV positive - only bile + feces didn’t have any but they’re hard to find anything on PCR

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20
Q

does having BVDV suck for the animal

A

yes its extremely immunosuppressive

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21
Q

two biotypes of BVDV

A

cytopathic and noncytopathic

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22
Q

what causes cytopathic BVDV

A

a mutation in NS2/NS3 gene which causes disease to deteriorate every mucosal surface of body

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23
Q

can you transmit the mutation of BVDV

A

No, same as FIP

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24
Q

mucosal disease

A

other name for cytopathic BVDV (mutation has occurred)

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25
Q

how to treat mucosal disease

A

euthanize

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26
Q

why does mucosal disease exist?

A

we don’t know - probably there’s an evolutionary reason but we haven’t found it yet

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27
Q

is it hard to get rid of BVDV

A

very hard

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28
Q

Alberta seroprevalence of BVDV 1 & BVDV 2

A

28.4 % and 8.9%

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29
Q

Alberta herd level seroprevalence of BVDV 1 & BVDV 2

A

53.4% & 19.7%

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30
Q

is BVDV control voluntary in NA

A

yes, and various European countries and regions have demonstrated that measures on a voluntary basis are inadequate to achieving freedom from disease

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31
Q

where is an easy place to get diagnostic sample for BVDV

A

ear notch

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32
Q

is finding PI animals then killing them a successful control strategy

A

yes, very effective! Ear notch ASAP & if PI, euthanize

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33
Q

when finding PIs, where should you start?

A

-serological evaluation of oldest non-vaccinated animals (6 months + as passive immunity is fading but not vaccinated yet)
- Bulk tank PCR (then individual ELISA)

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34
Q

Individual animal assessment after bulk tank

A

Ear notch, blood, or milk ELISA

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35
Q

is ear notch or serum a better sample for detecting BVDV?

A

ear notches because in serum, antibodies are already attached to virus so harder to find

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36
Q

if you have many cows and one is way smaller, which one is likely to be the PI?

A

the way smaller one

37
Q

Has vaccination changed BVD prevalence over time?

A

no, because the vaccines do not always contain the correct strain

38
Q

are there many or few vaccination options for BVDV

A

many! Modified live & killed vaccines both available

39
Q

is vaccination common fro BVDV

A

yes, >90% of cow calf producers in Western Canada vaccinate their cows and >95% of their replacement heifers against BVDV (survey of 93 herds)

40
Q

are dairy or beef herds more likely to have PIs

A

dairy because there are always pregnant animals around

41
Q

why is it so devastating on unvaccinated beef herds when virus gets introduced?

A

synchronized breeding (all fetuses approximately the same age)
almost all or all calves become PI (if BVDV comes in at the 2-4 month mark)

42
Q

What does vaccinating the PIs out of the herd mean?

A

vaccine induced mucosal disease - inject animal with cytopathic BVDV and animal won’t be able to respond to it as immunosuppressed - this causes mucosal disease & the animals eventually die

43
Q

does vaccinating the PIs out of the herd work?

A

no! First, VERY inhumane :( and only about 25% of PIs will succumb to mucosal disease after vaccination

44
Q

most effective BVDV strategy

A

1) find PI and euthanize
2) Make sure no new PIs for 1 year
3) close farm ideally
vaccinate between 6 months & 1 year

45
Q

What does BLV stand for

A

Bovine Leukosis Virus

46
Q

Why is BLV important in dairy

A

-Causes about 3% less milk per infected cow
-Infected cows are 23% more likely to get culled than non-infected
-Clinical Leukosis causes losses
-Export restrictions
-Animal Welfare
-Consumer concerns

47
Q

why is clinical leukosis bad

A

-Death of infected animals
- Condemnation of carcasses

48
Q

the greater the number of BLV positive animals, the __________ average milk production

A

lower

49
Q

are BLV+ cows more likely to be culled

A

Yes - but we don’t know why.

50
Q

why are BLV+ animals more likely to be culled

A

we dont really know but maybe B cells are infected which decreases immunity so maybe that causes more lameness, mastitis, metritis, and they give less milk, fat, and protein

51
Q

has BLV been increasing in prevalence in USA?

A

yes - 1975 was 10% and in 2017 was 43%

52
Q

CanWest DHI sample - prevalence AB (herd-level and individual)

A

84% herd-level nd average 40% of animals within a herd were infected

53
Q

where does BLV infect

A

B lymphocytes (CD5+)

54
Q

BLV makes a copy of its genome and inserts it

A

in the DNA of the cow (Provirus)

55
Q

BLV Infection leads to 3 different versions of clinical signs

A
  1. asymptomatic/aluekemic stage
  2. Persistent lymphocytosis
  3. Leukemia/Lymphoma
56
Q

BLV Asymptomatic/Aleukemic stage

A

don’t have increased amount of WBC in blood

57
Q

BLV Persistent lymphocytosis prevalence and clinical signs

A

30% of animals infected - always have increased WBC in blood

58
Q

BLV Leukemia/Lymphoma prevalence and clinical signs

A

0.1-10% of the Persistent lymphocytosis animals
develop tumours

59
Q

when BLV happens, what happens to B and T cells

A

polyclonal expansion of B cells which somehow causes abnormal function of T cells and monocytes (cytokine production and surface receptor expression alterations)

B cell # increase & at same time T cell # decrease

60
Q

how does cancer of the white blood cells develop?

A

-clones of B cells may become pathogenic and become tumours
- provirus induces genes upstream and downstream which can induce oncogenes
- can also induce genes in trans which produces tumours somehow

61
Q

what is a provirus

A

the genetic material of a virus as incorporated into, and able to replicate with, the genome of a host cell.

62
Q

what does retrobulbar process leading to exophthalmus mean

A

tumour tissue grows and pushes eyes out of their socket - if you see this, check for BLV

63
Q

can BLV lead to generalized edema

A

yes, means circulation isn’t going well

64
Q

can BLV lead to enlarged lymphnodes

A

yes

65
Q

can BLV lead to cardiac lymphosarcoma

A

yes - tumour tissue around heart & can also cause lymphosarcoma of spleen and intestines

66
Q

how is BLV transmitted between animals

A

blood, colostrum, milk, in the uterus, and natural breeding (not through semen but through wounds during mounting)

67
Q

when should you do an ELISA for BLV

A

36 days post infection - retrovirus so won’t detect it earlier

68
Q

when should you do a PCR for BLV

A

26 days post infection

69
Q

does BLV have variation in proviral load in blood?

A

yes - wide variation in peak proviral load. Proviral load is established early following infection

70
Q

BLV - how does number of viral copies in blood affect infected animals?

A

increased number of viral copies in blood - more likely to be leukemic animals

71
Q

is testing for BLV infection difficult?

A

no, a relatively simple antibody test that is very reliable, quick, not expensive

72
Q

what can you test for BLV infection

A

blood and milk

73
Q

should you test for BLV

A

yes, essential for a targeted control program + monitoring progress. Also part of proaction

74
Q

how do you get rid of BLV?

A

prevent new infections!!! Find management practices that involve blood, colostrum & cause transmission & change them then MONITOR !!!

75
Q

Examples of management practices that spread BLV

A

-colostrum
- ear notcher
-reusing the same needles
-flies
-using same rectal sleeve
-using the same hoof trimmer
- natural breeding

76
Q

BLV - which animals should you test?

A

introduced animals, any animals that leave farm (cattle shows, etc)

77
Q

most important causes of BLV infection

A

blood & colostrum spread

78
Q

is management prevention of BLV hard?

A

YES! many variables

79
Q

BLV- why is the proviral load of animals important?

A

gives a good idea of which animals to cull asap (High proviral load) vs can keep longer (low proviral load)

80
Q

BLV - the more proviruses an animal has, it has a(n) ______________ chance of transmitting the disease and a(n) ____________ probability of getting tumours

A

increased, increased

81
Q

do proviruses make products

A

yes

82
Q

what do provirus products do

A

we don’t know

83
Q

what is the threshold for considering culling an animal?

A

50% proviral load

84
Q

if an animal has increased lymphocytes, what also increases

A

proviral load

85
Q

is there a vaccine for BLV

A

no, but management practices can reduce virus burden in herd

86
Q

is there a vaccine for BVDV

A

yes - and works very well but will not eradicate the virus from popn

87
Q

has BVDV or BLV been eradicated in many western countries?

A

BVDV

88
Q
A

VETM 422: Virology (20 decks)

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