julia ridpath national animal disease center ames, ia€¦ · mlv - 65% hobi-like viruses ... may...
TRANSCRIPT
Julia Ridpath
National Animal Disease Center
ARS/USDA
Ames, IA
What’s in a name?
BVD
Umbrella term for a wide range of clinical presentations
○ Acute and persistent
○ Reproductive
○ Enteric
○ Respiratory
○ Immunosuppression
First causative agent isolated called
○ Bovine Viral Diarrhea Virus (BVDV)
Pestivirus genus
HoBi-like virus
BVDV3
Atypical pestivirus
BVDV1
BVDV2
HoBi-like
HoBi-like virus reports
Strain/
reference
Temperatu
re
Respiratory
signs
Decrease in
WBC* Viremia Shedding Seroconversion
HoBi_D32/00/
Schirrmeier et
al. 2004
Mild
increase
No clinical
signs
Slight
leukopenia
+
dpi 5
Nasal shedding
from dpi 3 to 6 +
Italy-1/10-1/
Decaro et al.
2011
40°C at dpi
3 and 7
Mucoserous
nasal discharge
from dpi 3 to 10
Reaching
about 50%
from dpi 3 to
10
+
dpi 5 to
24
Nasal and fecal
shedding from dpi
5 to 21 and 7 to
21, respectively
First detected at
dpi 14. Median
titer of 512 at dpi
21-28
Th04_Khonka
en/ Larska et
al. 2012
Around
39°C at dpi
7 to 10
Conjunctivitis,
nasal and ocular
discharge and
moderate cough
Around 40%
from dpi 5 to
7
+
dpi 5 to 9
Nasal shedding
from dpi 5 to 7 in
nasal swabs
Mean titer at dpi
14 of 54 and
1763 at dpi 42
Bovine pestiviruses acute
infections
Compare clinical presentation of calves
following infection with;
High virulence BVDV2
Typical virulence BVDV2
HoBi virus
Results
Similar to typical virulence BVDV2
○ Low grade fever of short duration
○ Reduction in circulating lymphocytes
Impact of HoBi-like viruses on reproduction
Reproductive/PI infections
Inoculation of 7 pregnant heifers (85
days gestation) resulted in
•1 late term abortion
•2 calves that died within 24 hrs
•Hemorrhagic gut
•4 clinically normal calves that are
persistently infected with a HoBi like
virus
BVDV1 BVDV2 HoBi-like
Immunosuppression X X X
Reproductive disease X X X
Respiratory disease X X X
PI X X X
Mucosal disease X X X
Hemorrhagic
Syndrome X*
BVD
More accurate to say causative agent is
a Bovine Pestivirus
Bovine Pestiviruses – 3 species
BVDV1
BVDV2
HoBi-like viruses (BVDV3)
BVDV1 BVDV2 HoBi-like
1st report 1946 1987 2004
Asia X X X
South America X X X
Europe X X X
North America X X
Africa X X
Australia X
HoBi-BVDV antigenic relationship
Bauermann et al. 2013
NADC/Novartis Study
Determine protection afforded against two different HoBi-like viruses by killed and modified live vaccine* Serum from vaccinated cattle provided by
Novartis Animal Health ○ Study typical for vaccine validation
○ 25 animals per group
Results Detection of virus neutralizing antibodies
○ % Vaccinated cattle with neutralizing antibodies MLV - 65% HoBi-like viruses
KV - 34% HoBi-like viruses
Species/
subgenotype Virus
Lowest
titer
detected
Lowest titer
detected/
genotype
BVDV -1a
VM 4.5
4.3 7443 4.3
C24V 4.1
BVDV-1b
NY-1 4.5
4.4 NE 4.3
TGAN 4.5
BVDV-2a
890 4.5
4.4 1373 4.1
296nc 4.7
HoBi-like HoBi
D32/00 4.5 4.5
Diagnostic
Antigen capture ELISA Panpestivirus primers
Serology
* *
* *
Commercial ELISA
Test 1 – missed 22%
Test 2 – missed 78%
Calves, sheep, goats, pigs;
2 groups (3 to 5 animals);
Group 1 (GIn) inoculated with HoBi D32/00 and Italy-
1/10-1;
Group 2 (GEx) exposed to PIs (one PI from each virus
strain) for 30min, 2x/day for 7 days.
Based on virus isolation and/or seroconversion
both inoculation and PI exposure resulted in
transmission to all 4 species
Transmission study
• No reports of detection virus in cattle herds;
• Two contaminated FBS lots originated in US (Xia et al., 2011);
• Test of FBS lots:
72 US negative samples;
9 contaminated samples from US;
Pestivirus search:
RT-PCR;
ELISA;
Virus isolation.
Specific antibody search:
ELISA;
Virus neutralization test.
North America status - what we know…
Surveillance for bovine
pestiviruses
PI
Low incidence and lack of specific tests
May have sample stability problem with
HoBi-like viruses
Exposure – Serology
No problem with storage of samples
It is possible to differentiate serological
response
Detecting HoBi-like PI’s
Bauermann et al. 2014
PIs Ear notch - IHC
HoBi-like
BVDV1 BVDV2
Bauermann et al. 2014
Heifer/virus HoBi
D32/00 BVDV1 BVDV2
933
HoBi-like
53232 3327 2896
391 40342 416 955
622 53232 416 4390
478
BVDV1
1911 6654 1448
541 630 4390 478
578 274 630 137
902
BVDV2
1097 208 6654
911 1911 955 7643
935 1663 1448 7643
Neutralizing antibodies – heifers serum
HoBi-like PI generation
Bauermann et al., unpublished
Surveillance using samples from brucellosis testing program
Virus neutralization
- BVDV-1
- BVDV-2
- HoBi-like
Location of packing
plants
200 serum samples per month for a total of 2000 samples
1972 total samples
Results – Average titers
Just averaging titers is not very informative Variation among
cross reactivities developed by different animals
Variation among sera
○ High titer sera versus low titer sera
Comparative ratios
0
1
2
3
4
5
6
7
8
9
BVDV1 Log2 BVDV2 Log2
HoBi-like Log2
Comparative titer ratios
(3 X A)/(A+B+C)
Where A, B and C are titers against the three different bovine pestivirus species
Antibodies are specific for one species when ratio is 0.2 higher
6 categories –
No antibodies, Clearly BVDV1, Clearly BVDV2, Clearly HoBi-like, Clearly BVDV, Equivocal
0
200
400
600
800
1000
1200
1400
No antibodies Clearly BVDV
Clearly HoBi Eqivocal
Number of sera placed in
categories determined by
comparison of R values
Samples rated equivocal with higher titer against
HoBi BVDV1 titer BVDV2 titer HoBi-like
titer region
6.2 7.2 7.8 midwest
8.5 7.8 9.8 midwest
9.8 8.5 10.5 midwest
7.8 8.5 9.5 Mountain
west
8.5 8.2 9.5 Mountain
west
8.2 9.8 10.5 Pacific West
avg 8.2 8.3 9.6
Regional differences Exposure ranged from 81% to 96%
No antibodies
0
2
4
6
8
10
12
14
16
18
Midwest Mountain
West Northeast Pacific West South
Southeast US
No antibodies
No antibodies
Level of protection
0
10
20
30
40
50
60
70
< 16 16 - 256 > 256
BVDV1
BVDV2
HoBi-like
Little or no
protection Reduce
disease but
still shed
Reduce
fetal
infections
Fetal
challenge
study
All fetuses
were PCR
positive for
HoBi-like
virus
Issues that need to be addressed
What vaccine is best? Globalization of vaccine companies
○ Different bovine pestivirus species present in different geographic regions
Protection versus surveillance
Trade in fetal bovine serum Little if any regulation
Labeling of origin does not necessarily reflect where sera was collected
Cross contamination in processing
Introduction of HoBi-like viruses into Europe theorized to be via import of contaminated FBS
What doesn’t kill you doesn’t necessarily
make you stronger
30 days post infection with high virulence BVDV
Impact of infections on
developing immune system
There is a relationship between age of ruminants and susceptibility to infection
Indicates that there is a choreographed maturation process that occurs in the immune system
Thymus largest in neonate and involutes with age
Thymus induces maturation of other immune tissues
Stress and disease results in early involution
Aftermath of neonatal
infections
0
50
100
150
200
250
Th
ym
us
- c
erv
ica
l w
eig
ht
(g)
Non
infected Typical
virulence
Enhanced
virulence
Destruction of thymus
evident 14 post infection
Control
HoBi D32/00
Italy-1/10-1
►Thymus
0
1
2
3
4
5
6
20-30 30-40 40-50 50-60 60-70
Percentage of reduction
Thymus reduction in calves
Number of calves
Bauermann et al., unpublished
►Thymus Non infected
2 weeks after acute bovine pestivirus infection
Emerging pestiviruses besides
HoBi-like viruses Porcine
Bungowannah ○ Limited sporadic outbreaks
Atypical Porcine Pestivirus (Congenital tremors) ○ Newly identified using NGS
○ Preliminary results indicate widespread in US
Wildlife Giraffe
○ Several isolations, prevalence unknown
Pronghorn ○ Circulating in mule deer, antelope, mountain goat
and big horn sheep in US
Zoetes
Animal
Health