dr. laura greiner - reducing pathogen transmission at the feed mill

Reducing Pathogen Transmission at the Feed Mill

Laura L Greiner, PhDCarthage Innovative Swine Solutions,

LLC

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Introduction

• Dee et al. discussed fomite transfer of PRRS virus

• Any item entering the farm has the potential to be a fomite (including feed and feed trucks)

• Discussion of areas of greatest risk and opportunities to minimize the risk

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Understanding Potential Routes of Introduction of Pathogens

• Ingredients– Contaminated with pathogen from supplier– Many ingredients sourced outside of US

• Sludge/Contamination – Trucks contaminated during transport– Dump over grated receiving pit

• Farm delivery trucks • Personnel

Feed Mill Swabs at Time of a PEDv Break

FindingsNegative Suspect Positive Total

Office floor 1 1

Corn pit 2 2

DDGs/SBM/Limestone pit 2 2 4

Mixer 2 2

Feed trailer – outside 3 1 4

Feed trailer - inside 3 3

Feed truck - sock 1 1

Bulk trailer 9 2 11

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Feed Mill Risk Assessment Study

• Objective: To assess the risk of areas within a mill to test positive for either porcine epidemic diarrhea virus (PEDv) or swine delta coronavirus (PDCov)

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Methods• Twenty-four feed mills from various regions in the US in the

summer of 2014

• Samples (foot pedals of feed delivery truck, bulk ingredient unloading pit, inside mixer/pellet cooler, mill office floor, inside feed compartment on feed truck, and incoming bagged ingredient truck) were collected at each feed mill for up to 5 days

• The samples were submitted for PCR testing for PEDv and PDCov

• Data were analyzed as probabilities and risk assessments

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Findings• Of the feed mills tested, 75% of the mills were supplying feed to

PEDv positive herds and 21% were feeding PDCov positive herds

• No samples tested positive for PEDv– 5% of the truck foot pedals and 1% of the bulk ingredient pit tested

suspect for PEDv

• Porcine delta coronavirus was found on 3.4% of the foot pedals of the trucks and 2.2% of the office floors

• As the number of days increase, the probability of a positive/suspect result also increased to being less likely

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Floor Mixer Pedal Bulk Ingred CompPEDv+ Sample Days

18 Test ~+ 1 0.000 0.000 0.069 0.017 0.000 0.014

2 0.000 0.000 0.133 0.033 0.000 0.0283 0.000 0.000 0.193 0.049 0.000 0.0424 0.000 0.000 0.248 0.065 0.000 0.0565 0.000 0.000 0.300 0.081 0.000 0.069

PEDv-6 Test ~+ 1 0.000 0.000 0.000 0.000 0.000 0.000

2 0.000 0.000 0.000 0.000 0.000 0.0003 0.000 0.000 0.000 0.000 0.000 0.0004 0.000 0.000 0.000 0.000 0.000 0.0005 0.000 0.000 0.000 0.000 0.000 0.000

Probability of Any Positive Test Results by Sample Days

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Probability of PEDv+ in Mill Given Negative Test Results by Sample Days

Floor Mixer Pedal Bulk Ingred Comp

Sample Days

1 0.750 0.750 0.736 0.747 0.750 0.747

2 0.750 0.750 0.722 0.744 0.750 0.745

3 0.750 0.750 0.708 0.740 0.750 0.742

4 0.750 0.750 0.693 0.737 0.750 0.739

5 0.750 0.750 0.677 0.734 0.750 0.736

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Floor Mixer Pedal Bulk Ingred CompDELTAv+ Sample Days

5 Test+ 1 0.000 0.000 0.160 0.000 0.000 0.0002 0.000 0.000 0.294 0.000 0.000 0.0003 0.000 0.000 0.407 0.000 0.000 0.0004 0.000 0.000 0.502 0.000 0.000 0.0005 0.000 0.000 0.582 0.000 0.000 0.000

DELTAv? Sample Days8 Test+ 1 0.033 0.000 0.000 0.000 0.000 0.000

2 0.066 0.000 0.000 0.000 0.000 0.0003 0.097 0.000 0.000 0.000 0.000 0.0004 0.127 0.000 0.000 0.000 0.000 0.0005 0.156 0.000 0.000 0.000 0.000 0.000

DELTAv-11 Test+ 1 0.033 0.000 0.000 0.000 0.000 0.000

2 0.066 0.000 0.000 0.000 0.000 0.0003 0.097 0.000 0.000 0.000 0.000 0.0004 0.127 0.000 0.000 0.000 0.000 0.0005 0.156 0.000 0.000 0.000 0.000 0.000

Probability of Any Positive/Suspicious Test Results by Sample Days

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Probability of DELTAv+ in Mill Given Negative Test Results by Sample Days

Floor Mixer Pedal Bulk Ingred Comp

Sample Days

1 0.320 0.313 0.276 0.313 0.313 0.313

2 0.327 0.313 0.243 0.313 0.313 0.313

3 0.335 0.313 0.212 0.313 0.313 0.313

4 0.342 0.313 0.185 0.313 0.313 0.313

5 0.350 0.313 0.160 0.313 0.313 0.313

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Contamination Sites

Transport

• Feed Mill ingredient unloading– Sometimes difficult to unload from trucks– Ingredient pit - sized and contained to prevent

side spillage

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Establish a Traffic Pattern at the Mill for Ingredient Unloading and Feed Loading

Ingoing

Outgoing

Ingredient unloading-bulk

• Weigh at truck scales• Driver entrance area separate from feed mill

personnel-disinfectant mat• Define area to receive paper work: tickets etc.• Unloading area:– No direct access to rest of feed mill

• Ingredient drivers must stay in receiving area– Phone call to manager if problems– Cover ingredient pit after finished unloading

Ingredient Unloading

Loading-Complete Feed

• Feed driver entrance separate from mill personnel– Stay confined to load-out area and break room

area• Use flooring that allows material on the bottom of the

shoe to fall away (elevated flooring)• Receive paper work• Bathroom/vending area

Load-Out

Frozen Sludge

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Frozen Sludge

• Dee demonstrated that frozen snow can carry PRRS virus

• Snow runs the risk of falling into an ingredient pit during the time of unloading

• Careful removal of the snow may be required before unloading or extra bulk storage to allow for a non-delivery day if needed

Vermin Control

• Doors to remain closed on ingredient loading and unloading bays

• Bait stations located outside of feed mill

Feed Deliveries

• Establish a biosecurity pyramid• Wash feed delivery truck before moving up

the pyramid• Disinfect floor mats/pedals• Watch shoes between facilities

Ranking of Greatest Biosecurity Ingredient Risks

• How fast is inventory used?• How is the product received?– Bags/totes – Bulk ingredient– Liquid tank

• How is the bulk product stored before arrival?

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Survivability of PEDv in Ingredients

Dee, et al. 2015

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Understanding Storage of Bulk Ingredients

• Storage areas– Flat-• potential for bird contamination• likely overhead load-out

– Silos/upright storage• more bio-secure with bird control

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Storage Devices

• Bags/totes– Ensure manufactured product has been kept in a

clean storage facility for a desired period to reduce risk of active virus

• Liquid products– Can liquid fat be kept in a fat tank for a period of

week before use to allow for the heat to inactivate any potential virus?

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Feed Mitigation

• Products can be added to the feed for control of pathogens:– Organic acids – bacterial control– Feed disinfectants – Salmonella control

• Pelleting process can heat inactivate pathogens

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Conclusions

• Areas of risk are multi-fold

• Feed mills that are working with active facilities have a greater chance of having areas positive for the virus

• Strict biosecurity measures at the feed mill will help reduce the risk

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Acknowledgements

• National Pork Board• Fellow nutritionists for feed mill samples• Dr. Bob Harrell

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Thank you