Because the porcine epidemic diarrhea (PED) virus can be transmitted quickly in herds, it is imperative to diagnose PED immediately once symptoms are apparent. Once a PED infection occurs in piglets, symptoms are usually seen 15 to 24 hours later, and may last up to three days. For prewean piglets infected with PED, the mortality rate can be alarmingly high.

• Sows: watery diarrhea, loose feces, vomiting, off feed
• Weaners and Growers: acute watery diarrhea with no blood or mucus, vomiting, off feed
• Prewean Piglets: diarrhea, dehydration, vomiting, malnourishment, high mortality

Testing is the only way to identify PED

A laboratory test is the only way to positively identify PED, since clinical symptoms are similar to those associated with transmissible gastroenteritis (TGE) and other diseases.

There are three primary types of diagnostic testing available for PED:

1. Serum antibody: A positive enzyme-linked immunosorbent assay (ELISA) test detects whether there’s been exposure to the PED virus or if there was passive transfer of antibodies from sow to piglet. A negative ELISA test tells us that the animal has not immunologically responded to the virus, due to no exposure or very recent exposure, or that the animal was sufficiently exposed to the virus in the past and the antibodies have declined to non-detectable levels. Note: A negative ELISA test may not mean that PED is not present in the herd.
    
2. Fecal antigen/Oral fluid antigen: The polymerase chain reaction (PCR) test detects whether the virus or a portion of the virus was present at the time of sampling using small samples of RNA.
    
3. Environmental antigen: This PCR test detects whether the virus or a portion of the virus was present at the time of sampling using small samples of RNA. This test can help define the environmental level of virus following a break, or it can test the success of sanitation programs.

Work with your herd veterinarian to establish a testing protocol customized for your operation. The following tests may be appropriate for diagnosing PED status:

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Tips for PED testing

Below are several important things to keep in mind when testing for PED:

• Ideal pigs to sample are those acutely affected with watery diarrhea.
• Collect samples and immediately refrigerate.
• Send samples overnight to a laboratory using an insulated box with ice packs.
• Completely fill out laboratory submission form.

University diagnostic labs can conduct testing for PED, as well as provide a variety of other services. A definition of the cases that must be reported can be found on the USDA APHIS website.

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