dr. scott dee - feed biosecurity: a new approach to pedv control

Feed biosecurity: A new approach to PEDV control

Scott Dee DVM MS PhD Dipl;ACVM

Director, Pipestone Applied Research (PAR)

Topics

• Disclosure

• What happened to PEDV?

• Review– PRRSV vs. PEDV risk factors– PCR basics

• PEDV in feed: The Pipestone Experience (Jan 2014)

• Feed biosecurity

What happened to PEDV?

• 2014 vs. 2015: what a difference!

– Immunity?

• Long lasting

– Biosecurity?

• Much improved

– Feed?

• Awareness of risk

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Review of Risk Factors

Route PRRSV PEDV

Genetics YES YES

Personnel YES YES

Supplies YES YES

Transport YES YES

Air YES YES

Feed NO YES

PEDV PCR fundamentals

• 1. The PCR assay for PEDV is a semi-quantitative measure of RNA in a sample.

• 2. Values are reported in terms of Ct (cycle threshold).

• 3. The higher the CT value the lower the amount of RNA in the sample.– Ct values of 38-40 = negative

– Ct values of 15-25 = positive

© 2014 Pipestone Veterinary Services, PLLC

This document and any files transmitted with it are for the sole use of the intended recipient(s) and may contain confidential and privileged information.

This is new paradigm for both the veterinary profession and the feed industry. Feed is not a risk for PRRSV.

We come not to blame the feed industry but to ask if we can help. We are partners and must work together.

Our only goal is to prevent PEDV introduction to our sow farms. We simply want to understand the risk and

make a plan to deal with it.

Pipestone’s position on PEDV in feed



Pattern of sow farm infections May-December 2013

2 PS farms infected January 2014

3 sow farms infected within a 1 week period Farm biosecurity very high (filtered) No animal by-products in PS sow herds

Epidemiology Clinical signs of PEDV began 1-2 days following feed delivery &

consumption Bin location corresponded directly to the onset of clinical signs

Role of feed was challenging No literature or references to learn from.

Lack of sampling methods.

Lack of infectivity assays.

History

Temporal relationship of feed delivery, consumption and diagnosis of PEDV in affected breeding herds

Farm A B C

Feed delivery date January 6 January 8 January 9

Consumption date January 6-7 January 8-9 January 10

At-risk populationWest gestation

Room 2 GDU West Farrowing North gestation

Clinical signs January 9 January 10 January 12

Index casesWest gestation

Room 2 GDU West Farrowing North gestation

PEDV diagnosis January 9 January 11 January 13

PEDV Ct in feed 20.25 22.60 19.50



On farm investigation

PEDV RNA was detected at the following points:1. Dust particles from exhaust fans2. Ground directly below exhaust fans3. External concrete pads at critical access

points4. Farm personnel: nares, hair, hands,

footwear5. Vehicle cab and tires6. Feed truck driveway entrance to mill7. Feed truck exterior upon arrival to mill8. Interior walls of suspect feed bins



Hypothesis: A high environmental viral load is source of feed contamination

1. A farm becomes infected2. The ground surrounding the buildings become

contaminated via virus in exhaust air dust3. Exterior critical access points become contaminated4. Delivery vehicles (feed truck) and personnel access farm

premises and become contaminated 5. Vehicle travels back to mill carrying virus on tires,

undercarriage and cab6. Truck enters mill & contaminates the floor7. Droppings from truck and spilled feed swept into the pit8. Batches of feed are contaminated, delivered to farm 9. The cycle repeats and the environmental load grows



Hypothesis: PEDV infection will occur following ingestion of contaminated feed.

Proof of concept: swine bioassay

Study design*

3 groups 1. Treatment group: Pigs consumed feed containing

PCR-positive samples from the 3 feed bins previously described.

2. Positive control group: Pigs consumed feed spiked with stock virus.

3. Negative control group: Pigs consumed feed containing saline placebo.

*Pigs were allowed to consume treated feed via natural eating behavior



Controls & Biosecurity1. BSL-3 facility (SDSU ARW)

*Documented free of residual virus

2. 3 week old PEDV-naïve pigs*Tested on arrival

3. PEDV-free feed*Tested prior to use

4. ARW personnel biosecurity plan (PAR validated procedures)*Negative control room > Treatment room > Positive control room

*Change of coveralls, boots, P95 mask and gloves between rooms*Shower in and out of facility

Ct = 20.65One-time application

PEDV feed bioassay: Summary of test groups

Date DPI Ct (AM/PM) Clinical Ct (AM/PM) Clinical Ct Clinical

Jan 17 0 neg neg neg neg neg neg

Jan 18 1 neg neg neg neg neg neg

Jan 19 2 neg neg 29.63/15.21 V/D neg neg

Jan 20 3 neg neg 16.06 neg neg

Jan 21 4 34.09/18.94 Diarrhea 15.48/23.19 Diarrhea neg neg

Jan 22 5 28.89 Diarrhea 15.79 neg neg

Jan 23 6 15.01/14.59 V/D* 16.94 neg neg

Jan 24 7 Study terminated

GI tractPCR (+)IHC (+)Lesions

GI tractPCR (+)IHC (+)Lesions

GI tractPCR (-)IHC (-)No lesions

Time Treatment Positive control Negative control

1. Could the bin samples used in the bioassay have been contaminated during the collection process?

Unlikely.

Protocol reduces the risk that sampling instruments were contaminated during accessing the bin.



Not that we have detected.

Adjacent bins do not always test the same. We have identified PEDV-infected farms with

negative feed bins. 4 farms on record.

1 farm tested bins multiple times over a 10 day period during an acute outbreak All bins negative

2. Do positive farms always have positive bins?

Suggests that routine contamination of bins secondary to environmental challenge does not always occur.



Not that we have detected.

We have identified PEDV-negative barns with negative feed bins. 4 farms on record All bins negative

3. Does the sampling method produce false positive results?

Indicates that the sampling method may possess a high degree of specificity



4. Was there room-to-room contamination during the bioassay?

No. Sequencing indicated clear differences in

strains. Cell-adapted isolate vs. field isolates. 963 bp to 1439 bp region

Negative controls remained negative.

Proves that the results of each group were the outcome of its respective strain and not due to cross-contamination.



5. Can we replicate the bioassay?

Yes. PAR has now conducted the following studies,

each involving a bioassay control: Assessment of PEDV viability in feed during periods of

diurnal temperature variation.

Evaluation of SalCURB as a means to reduce the risk of PEDV infection through contaminated feed.

Duration of PEDV viability in feed at 40 C.

Validates the natural feeding behavior model.



Conclusions

This is proof of concept of PEDV transmission through the consumption of contaminated feed. BMC Veterinary Research, 10:176, 2014.

The risk of feed as a vehicle for PEDV introduction into a farm is real. Both mechanisms (contaminated ingredients vs. environmental

contamination) must be recognized and managed. We must manage other risk factors as well.

What can we do?

We can’t even go to Hawaii and be safe from PED!

Immediate actions • Veggie diets

– Animal products removed in GDU and sow diets– Milk replacer removed

• Mill biosecurity– Points of risk identified (PAR)

• Office• Animal by-products• Trucks• Driveways• Dump pit

– Sanitation• Facilities

– Dry footbaths (Traffic Cop)

• Trucks– Synergize

Long-term actions

• Feed treatment

– Heat

• Pelleting time & temperature (PAR)– Heating feed to 1850 for 1 minute kills PEDV

– Feed is still PCR-positive but virus is no longer viable

– Chemical

• SalCURB (Kemin)

• Termin8 (AntiTox)



Introduction to SalCURB

Test Article: Sal CURB®brand ASF liquid antimicrobial, Kemin

Industries, Inc., Des Moines, IA

Description and Approved Use: A premix of aqueous formaldehyde solution 37% (for maintenance of complete animal feeds or feed ingredients Salmonella-negative for up to 21 days) and proprionicacid (as a chemical preservative for control of mold in feed or feed ingredients). Reference 21 CFR 573.460.

Disclaimer: Sal CURB®brand ASF provides effective Salmonella

control for up to 21 days; however, Sal CURB ASF is not approved for use by the U.S. Food & Drug Administration or the U.S. Department of Agriculture as a treatment for Porcine Epidemic Diarrhea Virus (PEDv).

Kemin process: Strict, high QA/QC, highly ethical company.



In vivo evaluation of a liquid antimicrobial (SalCURB) to reduce the risk of PEDV infection via contaminated feed BMC Vet Res 2014, 10:210

Objective: Determine whether pigs fed SalCURB treated feed can remain PEDV-free despite consistent exposure to virus via contaminated feed.

Hypothesis: The desiccant property of formaldehyde induces an anti-viral effect.

Bioassay design:As described

Date DPI PCR Clinical PCR Clinical PCR Clinical

3/20 0 neg neg neg neg neg neg


3/22 2 neg neg 19.98 neg neg neg

3/23 3 neg neg 16.32/18.84 Diarrhea neg neg

3/24 4 neg neg 17.10 Diarrhea neg neg

3/25 5 neg neg 16.07/15.70/16.58 V & D neg neg

3/26 6 neg neg 22.13 V & D neg neg

3/27 7 neg neg 21.20 Diarrhea neg neg








Necropsy 15 GI neg No lesions GI positive (5/5 pigs) Lesions GI neg No lesions

Pig data SalCURB treated (+) Controls (-) Controls

Treatment (SalCURB) group

Positive controls

Change in PEDV Ct in feed by groupthroughout the study period

0

5

10

15

20

25

30

35

40

45

Treatment Ct

Pos control Ct

Neg control Ct

0 1 3 5 7 9 11 13 15

PED

V C

t

Study day

P < 0.0001

Mean Ct = 35.55

Mean Ct = 25.15



1. Under the conditions of this study, the use of SalCURB appears to be a strategy for reducing the risk of PEDV infection in contaminated feed, based on the following observations:

a. The inclusion of SalCURB at labeled dose prevented PEDV infection and clinical disease in naïve pigs.

b. In the absence of SalCURB, pigs allowed to ingest PEDV-contaminated feed became infected at 2-3 DPI.

c. The inclusion of SalCURB had a negative effect on viral load in feed.

Conclusions

Current studies• PEDV survival in feed

– Complete feed at 40 C • Viable out to 21 days

– Ingredient survival under ambient winter temperatures• In process

• SalCURB– Duration of action

• 21 days

– Spectrum of activity• Enveloped & non-enveloped RNA viruses

– Effect on nutrient density and digestibility• No negative effect

– Effect on performance• No negative effect

– Dose titration• Underway

– Impact on virus survival in feed ingredients• Underway

Conclusions

• The risk of feed as a vehicle for PEDV infection has now been proven.

• Control options include:– Removal of animal by-products– Mill biosecurity– Feed treatment– Vehicle sanitation

• In combination, these actions have assisted in reducing the incidence of PEDV this winter.

dr. scott dee - feed biosecurity: a new approach to pedv control

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