Porcine Endemic Diarrhea Virus:
Quick Facts and Management Tactics
Pat Hoffmann, DVM
Director of Health & Biosecurity
Porcine Endemic Diarrhea Virus (PEDV) was confirmed in the United States by Iowa State University and the National Veterinary Services Laboratory on May 17th, 2013. For weeks prior to that veterinarians were describing TGE-like outbreaks despite negative lab reports. Although this is the first known detection in the United States, PEDV exists in many parts of the world including Europe and Asia. Thus, PEDV is not considered a foreign animal disease in the US, but rather a “transboundary” disease. It is also not on the World Organization for Animal Health’s (OIE) list of reportable diseases for the US or Canada. PEDV does not affect people and is not a food safety concern.
PEDV is a member of the Coronavirus family. Other members of this family include Porcine Respiratory Coronavirus (PRCV), Hemagglutinating Encephalomyelitis Coronavirus (PHE), and the most notable Transmissible Gastroenteritis Virus (TGEV). Different strains of PEDV do exist with virulence dependent upon the spike (S) gene sequence.
The clinical signs for PEDV are very similar to TGEV including severe acute watery diarrhea, vomiting, and anorexia. It is reported that in naïve herds, suckling pig mortality can be as high as 100% during the initial weeks of the outbreak. In feeder and growing pigs mortality can reach 5%, with most animals showing signs of diarrhea, anorexia, and depression. The incubation period ranges from 1-5 days with viral shedding lasting up to 9 days.
Transmission of PEDV is primarily through the fecal-oral route from pig to pig. It is also imperative to prevent transmission via people or equipment. People can carry the virus on their boots, clothing, gloves/hands, etc. Equipment such as dirty trucks, trailers, power washers, portable chutes, etc. can also be a source of contamination. It is best to have site-specific people and equipment; however, when that is not an option strict biosecurity should be followed (wash, disinfect, and dry). Currently swine trailers returning from packing plants and returning isowean trailers pose the greatest risk of infection.
Although PEDV and TGEV viruses are related and the clinical signs are very similar, there is no immune cross-protection. In the event of a PEDV outbreak, currently the best means of protection comes from aggressive bio-feedback. The primary goal is to ensure that EVERY animal on the farm is infected AS SOON AS POSSIBLE. Bio-feedback includes fecal material and intestinal tracts from acutely infected piglets. During the early stages of the disease collecting enough of this material will not be a problem but it might be wise to freeze samples should re-exposure be necessary.
When a PEDV outbreaks occurs a “load, close, and expose” approach similar to a PRRS outbreak should followed. Loading the farm with the replacement gilts necessary for a minimum 3 month farm closure and immediately exposing the entire farm is the fastest way to cut the virus off. Utilizing and monitoring sentinel animals for 4 weeks prior to resuming gilt introductions should also help determine if the virus has been eliminated. It must also be noted that bio-feedback is not without the risk of exacerbating other pathogens (i.e. PRRS) and immunity from feedback is not lifelong.
Preventing the spread of PEDV should be everyone’s main focus. It is important to reiterate that strict attention to the movement of pigs, people, and equipment are all equally important. Sitting down with all farm employees and reviewing your current biosecurity protocols would be a great first step. A good protocol already in place for other pathogens (i.e. PRRS, TGEV) should greatly assist with preventing PEDV from entering your farm. A basic plan includes:
- Only traffic that is absolutely necessary is allowed onto the premises. This includes pigs, people, and equipment.
- Strict downtimes are enforced for anybody entering facility.
- Visitors are only allowed to enter only if absolutely necessary.
- A log of all human traffic is kept including each person’s previous contact with swine-related facilities.
- In order to enter the facility showering is mandatory and fresh boots and clothing will be provided.
- All equipment and supplies entering the farm should be thoroughly cleaned, disinfected, and allowed to dry.
- Isolation of new stock is recommended
- Particular attention should be given to disposal of dead stock, especially if rendering.
The latest summary released by the Veterinary Diagnostic Labs in Iowa, Kansas, South Dakota, and Minnesota reported 199 confirmed positive farms including 47 sow farms. The farms range in distance from Colorado to Pennsylvania and from Minnesota to Oklahoma. Although the total number of farms effected will continue to rise (the infected pigs that survive have to go somewhere) reports indicate the sow herd outbreaks are slowing down.
There is currently a collaborative effort to find out how PEDV entered the US. Positive herds are being surveyed to examine how the virus suddenly could have shown up in herds all across the Midwest. Due to the dissemination of positive cases across multiple states and different production systems, much of the current focus is on testing feed ingredients and their sources. Currently researchers are trying to use conventional testing methods to detect the virus. However, these tests are not validated for testing feed nor is there any scientific literature linking PEDV transmission via feed. In addition, feed has never been linked to PEDV outbreaks in Europe or Asia. Without a validated test for feed there is no guarantee that negative feed results are free of PEDV. Therefore, sampling and testing of feed for PEDV is not warranted without clinical signs present.
At the time of writing this article there were no confirmed positive cases in Canada and it is Genesus’ goal to do whatever we can to keep it that way. Due to the nature of our domestic business in the both Canada and the United States, Genesus has been fully committed to upholding the highest transportation biosecurity guidelines set in place by both the American Association of Swine Practitioners and the Canadian Swine Health Board.
When dealing with and preventing PEDV there really is no difference when compared to TGEV. Good biosecurity protocols already in place for farm entry and transportation should eliminate the risk of bringing PEDV onto your farm. The biggest concern is that the entire US swine herd was naïve and the source of the outbreak is yet to be determined. This outbreak has confirmed, at least for me, that swine producers and veterinarians can achieve a lot when working collaboratively to find the best science-based solutions. The industry will survive.