Porcine Epidemic Diarrhea Virus (PEDV)

Albert Rovira, DVM, MS, PhD Veterinary Diagnostic Laboratory

Porcine Epidemic Diarrhea

• PED is caused by a coronavirus (PEDV)

• PEDV causes diarrhea and vomiting in swine of all ages

• High mortality in piglets under 2 weeks of age

Porcine Epidemic Diarrhea

• PEDV first described in Europe in the 70s

• PED currently not a problem in Europe

• PED is an important problem in Asia

Porcine Epidemic Diarrhea

• PEDV replicates in the epithelial cells of the small intestine

• Incubation period: 1-2 days

• Shedding in feces: 7-11 days

• Immune response: mucosal and serological: serum antibodies at 7-14 dpi

Source: AASV

Diagnostics

• Same basic guidelines of diarrhea diagnostic workups

• Select live, acutely affected pigs with diarrhea

• Perform necropsy and collect samples within 15 minutes of euthanasia

• Gross lesions: liquid intestinal contents, thin-walled intestines?

Sample collection

• Small intestine:

– 6 sections representing the whole length of the small intestine

– 10 cm segments fresh and 2 cm segments fixed

• Other tissues for a complete workup and to rule out differential diagnoses

– Stomach, colon, tonsil, lymph node, lung, heart, spleen, liver, kidney -- fresh and fixed

Other sample types

• Feces

• Fecal swabs

• Oral fluids

• Feedback material

• Environmental swabs

• Feed

PEDV diagnostic tests• Virus isolation:

– Difficult to grow in vitro

• Electron Microscopy: – low sensitivity

• Histopathology:

– atrophic enteritis

– same as TGEV and Rotavirus

• Real time PCR:

– sensitive and specific

– available in US laboratories

PEDV diagnostic tests

• IHC, ISH:

– less sensitive than PCR

– good for research, retrospective studies

• Serology:

– Indicative of previous exposure

– IFA/IPMA: will be available first

– ELISA: available in Asia, under development in the US

Testing protocols

• Diagnostic investigation in farms with diarrhea:

– Tissues from acutely affected pigs

– Fecal samples: 15 samples in pools of 5 (3 PCRs)

– Oral fluid samples from 2 pens

• Monitoring the status of farms with no diarrhea:

– Fecal samples: 15 samples in pools of 5

– 2 oral fluid samples

– 10-15 serum samples for serology

Testing protocols

• Monitoring the status of positive sow farms after herd

closure

– Fecal samples: 30 samples in pools of 5

– Serology on sentinels?

• Example:

– 8 wks after clinical signs: 10/10 positives

– 12 wks after clinical signs: 7/30 positives

– 14 wks after clinical signs: 1/30 positives

First cases observed in May

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>100 positive submissions in 2 months

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Negative

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Were we ready for a foreign animal

disease outbreak?

• VDLs:

– Early identification of the disease

– PCR test available within days

– Real-Time PCR test available within 2 wk

(results in 24h)

• Immediate involvement of Universities,

USDA-APHIS, AASV, NPB

Sharing of lab results to obtain a

national monitoring system for PED

• U of Minnesota and ISU combined results -

database maintained at ISU

• Combined database transferred to USDA-APHIS–

NAHLN

• Weekly summary

• Collaboration Universities–USDA–AASV-NPB

MN VDL + ISU + SDSU + KSU + OHADDL

Distribution of PED positives

Courtesy of Dr. Dane Goede

Limitations of current national

monitoring system for PED

• Detail of the data: state, farm type, sample type,

result

• Quality of the data: missing/wrong data

• Quality of the data: reported by submission, not by

premise

• Include premises ID in submission form and give

permission to VDLs to share that info with national

database

Where did PED come from?

• Asia, Europe,…???

• How did it get here?

– Pigs

– People

– Feed

– Wildlife,…

• U of M, AAVLD and USDA-CEAH:

epidemiological study to answer these

questions

Courtesy of Doug Marthaler

Sequencing of

Spike gene

Did it come from feed products?

• Some feed ingredients tested positive by PCR

• We performed a bioassay to figure out is it was live

virus

• 3 pigs inoculated with PBS (negative controls)

• 3 pigs inoculated with PCR-positive feed products

(bioassay)

• 3 pigs inoculated with PCR-positive fecal samples

(positive controls)

Results bioassay

Vomit Diarrhea PED PCR Atrophic

enteritis

NEG Control No 1/3 0/3 0/3

Bioassay No No 0/3 0/3

POS Control YES 2/3 3/3 3/3

CONCLUSION: feed can contain PEDV nucleic acid

that is not infectious but can test positive by PCR