bvd diagnostics goals, strategies and best tests...m. daniel givens, dvm, phd, dact, dacvm bvd...

M. Daniel Givens, DVM, PhD, DACT, DACVM

BVD Diagnostics—

Goals, Strategies and

Best Tests

BVD: An Industry Prevention

Strategies & Solutions Forum

Do you have BVD in your herd?

Yes No Maybe

Corporate

Distribution Centers

Major Food Services

Corporate

Distribution Centers

Major Retailers

Distributor/Broker

Industry Segment

Retail Outlets/ Food Services

Rural & Urban United States

End User

Rural United States

Pre-conditioners/Backgrounders8 to 14 months 500 to 900 lbs

Feedyards

Packers

Commonly shipped to Midwest

14 to 18 months 900 to 1150 lbs

Calf age Calf weight

Birth to 8 months Birth to 500 lbsCow/Calf Producers

Typical U.S. Nationwide Beef Supply Chain

1. Do you have BVD in your herd?

Yes No Maybe

NAHMS 2007-08 Beef Cow-calf study

15.1%

24.0%

31.5%

25.2%

4.2%

0.0% 10.0% 20.0% 30.0% 40.0%

Had not heard of before

Recognized the name

Knew some basics

Knowledgable but with no testing

Knowledgable & tested in last 3 years

BVDV Knowledge of Producers from the Southeast


Yes No Maybe


2.6%

8.1%

31.9%

41.8%

15.6%

0.0% 5.0% 10.0% 15.0% 20.0% 25.0% 30.0% 35.0% 40.0% 45.0%


Recognized the name

Knew some basics



BVDV Knowledge of Producers with 200 cows


Yes No Maybe


2.6%

8.1%

31.9%

41.8%

15.6%

0.0% 5.0% 10.0% 15.0% 20.0% 25.0% 30.0% 35.0% 40.0% 45.0%


Recognized the name

Knew some basics



BVDV Knowledge of Producers with 200 cows

The intent to test for BVDV is not the same as testing.

(205 submitted samples of 306 ordered sample collection kits = 67%)

Herd Prevalence of PI calves (8 studies)

Report Reference

Data

collection

year

PI Prevalence Herd Prevalence

Houe et al. {439} 1995 7/5,481 (0.13%) 3/20 (15%)

Grooms et al. {1088} 2001 5/1,952 (0.26%)d 3/13 (23%)d

O'Connor et al. {1504} 2006 12/12,030 (0.09%)c 4/102 (4%)

Wittum et al. {1494} 1996 56/18,931 (0.3%) 3/76 (4%)

Fulton et al. {1496} 2006 26/4,407 (0.6%) 5/29 (17.2%)

Bolin et al. {1495} 1985 54/3,157 (1.7%)b 6/66 (9%)b

NAHMS {1646} 2007-2008 53/44,150 (0.12%) 18/53 (8.8%)

Lawrence & McClure {1535} 2005-07 3,489/866,602 (0.4%) 2,470/11,857 (20.83%)

Prevalence of PI calves (26 studies)

Report Reference

Data

collection

year

PI PrevalenceHerd

Prevalence

Hoar et al. {1500} 2004 3/900 (0.3%)

Grooms & Keilen {1145} 2000 6/332 (1.8%)

Munoz-Zanzi et al. {1190} 1999 2/434 (0.5%)

Houe et al. {439} 1995 7/5,481 (0.13%) 3/20 (15%)

Mawhinney et al. {1505} 2007 3/1,769 (0.2%)

Grooms et al. {1088} 2001 5/1,952 (0.26%)d 3/13 (23%)d

Stephenson et al. {1593} 2005 24/7,544 (0.3%)

Cornish et al. {1367} 2005 59/559 (10.5%)c

O'Connor et al. {1504} 2006 12/12,030 (0.09%)c 4/102 (4%)

Wittum et al. {1494} 1996 56/18,931 (0.3%) 3/76 (4%)

Fulton et al. {1496} 2006 26/4,407 (0.6%) 5/29 (17.2%)

Paisley et al. {309} 1996 8/1,201 (0.67%)a

Bolin et al. {1495} 1985 54/3,157 (1.7%)b 6/66 (9%)b

NAHMS {1646} 2007-2008 53/44,150 (0.12%) 18/53 (8.8%)

Report Reference

Data

collection

year

PI Prevalence

Cleveland et al. {1253} 2003 5/2,921 (0.17%)

Taylor et al. {352} 1992 51/560 (9.1%)

Taylor et al. {412} 1991 1/1,029 (<0.1%)

Loneragan et al. {1497} 1998 8/4,000 (0.2%)

Fulton et al. {1476} 2004 86/21,743 (0.4%)

Larson et al. {1478} 2004 3/938 (0.32%)

Loneragan et al. {1347} 2002-03 6/2,000 (0.3%)

Loneragan et al. {1347} 2002-03 36/1,383 (2.6%)

Loneragan et al. {1347} 2002-03 39/1,585 (2.5%)

Howard, et al. {104} 1988 12/1,538 (0.78%)

Lawrence & McClure {1535} 2005-07 3,489/866,602 (0.4%)

Yan, et al. {1686} 2006-2008 111/27,932 (0.4%)

From presentation by J. Lawrence at 50th AAVLD meeting October 2007.


Yes No Maybe

BVD virus is considered to not be in the herd if the herd has high pregnancy rates, few

aborted fetuses, no birth defects, excellent calf health and lacks diagnostic evidence for

BVD virus.


Yes No Maybe

BVD virus may be in the herd if the herd has clinical signs consistent with BVD (e.g., lower

than expected pregnancy rates, aborted fetuses, birth defects, low birthweight calves,

or poor calf health) but no diagnostic confirmation of BVD virus.


Yes No Maybe

BVD virus is in your herd if virus (not antibodies) has been detected in samples

from your herd (aborted fetuses, dead calves, or live cattle).

Why test?

• Increase market value of animals

• Ensure that a herd is free of PI animals

• Identifying individual PI animals spreading disease within a herd or group

Surveillance to detect

How??? 1

A. Question: Is BVDV circulating in the herd?

Methods to answer the question:Lowest Cost &

Least Reliable1.

2.

3+2.

4+2. Submit ear notches from young calves for validated pooled PCR testing.5+2. Submit ear notches from young calves for individual testing (ELISA or IHC).

Highest Cost &

Most Reliable6+2.

Submit blood samples for antibody detection from unvaccinated sentinel

animals that are 7 months of age and have experienced close contact with

all other animals in the herd at least one month prior to sampling.

Submit ear notches from young calves, non-calving females and bulls for

individual testing (ELISA or IHC).

Observe for clinical signs of disease. Submit samples from all aborted and

underweight calves for BVDV testing

Observe for clinical signs of disease

Persistently infected (PI) cattle are the source of ongoing exposure in herds with BVD virus, and they need to be identified and removed

prior to the breeding season. Will you do this?

Yes. If yes is selected, you and your veterinarian know who to test, when to test, and how to test. If not, please review info to define this question.

Help to define: Where do PI calves come from?

Which test should I use to detect PI cattle? Consideration of strategy of testing for PI cattle?

No. If no is selected, you are deciding to accept the cost of continued presence of the virus in your herd.

When should you test?

Which cattle should you test?

January

April

July

October

Calving Season

Breeding Season Bull BSE’s

May: wean calves &

pregnancy cows

August: strategic

summer deworming

March: castrate, dehorn,

and vaccinate calves

Intense

Biosecurity

Institute testing of calves

& introduce herd additions

Beef Cattle - Prebreeding Test of

Calves, Bulls, Cattle without Calves

Negative

Retain in

Herd

Positive

Sell for

Slaughter

Bulls and

Cattle without

Calves Remove Positive

Calves and Dams

from Herd

Prebreeding

Calves

Adapted from:

Kelling,et al,The Bov Pract, 34:1 (2000) 13-22

Remove Positive Calves and

Dams from Herd Prebreeding

Sell positive

calves for

slaughter

Test Dams

Positive Cow -

PI calf product

of PI cow

Sell for

slaughter

Only cow may

return to herd

Negative Cow -

PI calf from

acute infection

Adapted from:

Kelling,et al,The Bov Pract, 34:1 (2000) 13-22

Diagnostic Test Relative cost Specimen Used for Notes

Polymerase chain

reaction (PCR)Low to high

Serum, whole

blood, tissue

Identifying PIs and

acute infections

Rapid and sensitive on individuals.

Pooling reduces sensitivity.

Polymerase chain

reaction (PCR) of skinLow to high

Skin-usually

taken from earIdentifying PIs

Rapid and sensitive on individuals.

Pooling reduces sensitivity.

Immunohistochemistry

(IHC) of skinLow

Skin-usually

taken from earIdentifying PIs

Fresh or formalin-fixed samples.

Work closely with validated lab to

provide preferred sample.

Antigen-capture ELISA

(ACE) of serumLow Serum Identifying PIs

Rapid results. Serum testing may

be inhibited by passive immunity,

thus not recommended for young

calves.

Antigen-capture ELISA

(ACE) of skinLow

Skin-usually

taken from earIdentifying PIs Rapid results.

Virus IsolationModerate to

high

Serum, whole

blood, tissue

samples

Identifying PIs and

acute infections

Gold standard test for detecting

BVDV; however, expensive, slow

results and requires specialized

labs.

Immunoperoxidase Assay ModerateSerum, whole

bloodIdentifying PIs

Moderate time to results and

requires specialized labs.

Virus neutralization or

antibody ELISALow Serum

Identification of

virus exposure-NOT

for detecting PIs

Detects immune response (titer) to

BVDV.

Which test should you use to detect PI cattle?

Also cost appropriate

for individual samples

Not affected by

colostral antibodies

If I get a positive, how sure am I that the calf is PI?

If I get a negative, how sure am I that the calf is not PI?

When I “remove” a PI, what am I

going to do with it?

Follow-up surveillance is a critical aspect to assessing and maintaining your BVD control program. There are several options for this:

Yes If yes is selected, you and your veterinarian know how to assess the success of your BVD control program and ensure that no PI calves are maintained in your herd during the subsequent year.

No If no is selected, you are deciding to accept a risk of maintaining PI calves in your herd during the subsequent year.

Please select one.

Low est Cost &

Least Reliable

1.

2.

3+2.

Highest Cost &

Most Reliable

4+2.

Complete step #2 and submit appropriate samples from all young calves for validated

pooled PCR testing.

Complete step #2 and submit appropriate samples from all young calves for validated

individual testing.

Observe for clinical signs of disease (e.g., lower than expected pregnancy rates, aborted

fetuses, birth defects, low birthweight calves, or poor calf health). Submit samples from all

aborted and underweight calves for BVDV testing

Observe for clinical signs of disease (e.g., lower than expected pregnancy rates, aborted

fetuses, birth defects, low birthweight calves, or poor calf health).

#1. Individual animal testing for BVDV is tremendously rewarding to animal health and

financial productivity of a farm.

Agree Disagree Conflicted

#2. Individual animal testing for BVDV is tremendously rewarding to animal health and

financial productivity of a farm when PI cattle will be detected.

Agree Disagree Conflicted

A sensitive and specific screening test at the level of the pen or farm can appropriately motivate individual

animal testing!

Walter Coles

www.ablogabouthistory.com

Consumption Surface Sampling to Detect BVDV using PCR

1 2 3 4

Pen #1: Ten seronegative

calves commingled with two PI calves

Day 0 1 2 3 sample sample sample

20 min 2h 4h 6h 23.5h

Indicates that serum, whole blood, and nasal swab samples were collected from all calves between 20 min and 2 h after feeding to assess infection status of all animals.

Consumption surface sampling

Validation of a non-invasive, novel testing method

Seronegatives only

PI’s only

Day 3 4 5 6 7 8 9 10 11

Pen #2: Only two PI calves

sample sample sample sample sample

Pen #3: Ten seronegative, exposed calves

Day 3 4 5 6 7 8 9 10 11 sample sample sample sample sample

Results

Consumption surface swabs obtained within 6 h of feeding from pens containing commingled or PI calves were consistently positive for BVDV.

Time post-feeding

Sample handling (No. positive samples/ total samples tested)

Refrigerate 1 to 3 d Refrigerate 7 to 10 d Freeze 7 to 14 d

20 min 16/16 16/16 15/16

2 h 16/16 16/16 15/16

6 h 16/16 16/16 12/16

23.5 h 11/16 12/16 11/16

Conclusion

Results indicate that consumption surface swabbing within 6 h of feed consumption is a

sensitive and non-invasive method to determine if PI animals are present within a

group of cattle

Surveillance to detect

How???

1

2 Biocontainment to affect

OR

Biosecurity to protect

3 Vaccination

to keep in check

Factors impacting the detection of viral RNA of BVDV from consumption surfaces

• Acute vs. Persistent Infection (PI) • Variability in viral shedding from PI cattle • Presence of maternal antibodies in PI calves • Dilution of viral RNA

– Over a greater consumption surface area – With a greater number of cattle

• Characteristics of consumption surface • Swab used for sample collection • Ambient temperature • Direct sunlight • Precipitation • Humidity • Time between surface contact and sample collection • Sample handling • Time between sample collection and assay for viral RNA


• Acute vs. Persistent Infection (PI)

– PI only

• Variability in viral shedding from PI cattle

– Detects a PI (AU #18) that exhibits:

• low serum concentrations of virus (350 to 4,600 CCID50/mL)

• neutralizing antibodies to the strain with which she is infected

• Presence of maternal antibodies in PI calves

– Detected two PI calves (at 45 and 47 days of age) within a group of 30 calves via 1 swab of all feed & water buckets in 30 individual calf hutches


• Dilution of viral RNA – Over a greater consumption surface area – With a greater number of cattle – Detected one PI dairy heifer in a pasture containing approximately

120, 21- to 23-month-old pregnant heifers. One swab was taken of the 240 linear feet (73 meters) of polyethylene troughs in this pasture to detect the presence of a PI in a large group of heifers containing only heifers that previously tested negative by individual animal ear notch ELISA. After a positive consumption surface swab, follow-up testing using virus isolation from white blood cells identified the PI heifer that produced a positive test result upon retest using individual animal ear notch ELISA

• Characteristics of consumption surface – Prior testing has focused on polyethylene, rubber, and concrete feed

trough and water trough surfaces. Swabs have been developed to withstand swabbing of concrete troughs.


• Swab used for sample collection – Optimized for durability and diagnostic sensitivity

• Ambient temperature • Direct sunlight

– Repeated positive results achieved when swabbing PI feed troughs at 6 hours post contact at:

• -3 °C (27 °F) which were protected from exposure to sunlight • 34 °C (93.2 °F) which were provided exposure to direct sunlight. Under these

conditions, the temperature of the black polyethylene surface of the feed trough exceeded 50 °C (120 °F).

• Our efforts have thus far been unable to identify a minimal or maximal ambient temperature that would prevent detection of viral RNA of BVDV from PI cattle.

• Precipitation – Repeated positive results achieved when swabbing PI feed troughs

during light to moderate rainfall.

• Humidity – Repeated positive results at 44 to 92% humidity.


• Time between surface contact and sample collection – Research results indicate that sample collection within

6 hours of trough contact will provide repeatable and diagnostically sensitive results.

• Sample handling – Research results validate refrigerated storage of

diagnostic samples.

• Time between sample collection and assay for viral RNA – Research results validate refrigerated storage of

diagnostic samples up to 10 days after collection.

bvd diagnostics goals, strategies and best tests...m. daniel givens, dvm, phd, dact, dacvm bvd...

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