What will be The Long Term Effects of Pedv After Exposure?

By Thomas G. Gillespie

As the Spring weather tries to break through on a winter that doesn’t seem to stop, many producers are still apprehensive about Porcine Epidemic Diarrhea virus (PEDv). About a year ago, PEDv became active in the United States.

Since it was a new pathogen to our country, new diagnostic procedures were quickly developed for rapid detection of the virus. The heavy blanket of snow and cold weather has definitely not helped in containing this new disease for producers. This virus is similar to Transmissible Gastroenteritis Virus (TGEv) in how it will thrive in cold wet weather, although it is more heat stable; therefore, summer and drying will reduce the incidence of outbreaks, but will not completely stop them.

For those of us that like to raise roses, the rose bushes are now showing themselves from underneath the heavy snow blanket that has been covering them for many weeks. This process of “uncovering” reminds me of the numerous lessons that have been learned about biosecurity over the past year, as well as, how to handle this virus once it does find a way into a sow unit. The virus itself has been elusive in how it has entered and therefore, infected some sow sites

One very pleasing aspect is how Pork Checkoff, USDA, National Pork Producers Council (NPPC), American Association of Swine Veterinarians (AASV), and research groups have tackled this problem and helped us quickly begin our understanding of this new pathogen. The American Association of Swine Veterinarians in collaboration with the Pork Board, NPPC, and USDA has quickly developed a survey to examine the epidemiology of PEDv. A cooperative project has been the updating of positive lab accessions that has tied diagnostic laboratories into the group with new cases being added each week as shown in chart 1.

Updated number of positive lab accessions by state

PEDv did not just spontaneously evolve in Midwest swine herds in April 2013. This virus was introduced into the United States pork production units from outside our country. The questions of how did it get here and where did it come from have been asked by many. These are “long-term” questions that will need to be answered so other pathogens are less likely to enter into our industry in the future.

This virus has caused the most economic concern in piglets less than two weeks of age. Therefore, biosecurity surrounding breeding herds has been the number one concern for the swine industry. Immediate changes that occurred began by limiting unnecessary visitors, having equipment go through a fumigation room prior to entering, thoroughly cleaning and disinfecting anything that drove onto the site, enforcing downtime requirements for people that needed to visit a site, as well as maintaining a log of visitors who entered the site. In addition, taking care of when and how animals were disposed, isolating newly arrived replacement animals, and incorporating oral fluid collections of these animals over and above routine diagnostic procedures performed, have vastly helped control this virus.

Additional biosecurity changes have focused on feed and feed mills. This virus quickly began known as an environmental contaminate with the potential of being “introduced” into a concentration point, i.e. any site that accumulated animals, and disseminated back out. This can happen with feed mills as well which puts numerous sites at risk of becoming infected.

One lesson learned is that little virus is needed to infect an animal or site. Diagnostic tests have shown that exceptionally large amounts of virus are produced inside the animals as it infects and multiplies within the intestinal tract, especially in the nursing piglets. All of these activities have led to changing routines and improving biosecurity programs. Even with this, the virus has found ways to infect very isolated and biosecure herds.

As our understanding about this virus as an environmental contaminant improves, the current approach is to develop protective immunity in sows by exposing the sow herd. The contaminated environment requires serious cleaning to reduce the amount of virus in the site’s environment. The units that use lagoon water to flush under the flooring have an additional risk factor to consider since the virus will survive in the lagoon water for several weeks. Each unit has constraints that need to be identified and discussed between the veterinarian and the farm’s staff, before success in controlling this virus will occur.

As veterinarians continue to work to limit economic losses of this virus, the benefits of improved biosecurity should be felt in controlling other pathogens as well, such as PRRS. Economic loses are coming in two forms:

“Biosecurity surrounding breeding herds has been the number one concern for the swine industry.”

As veterinarians continue to work to limit economic losses of this virus, the benefits of improved biosecurity should be felt in controlling other pathogens as well, such as PRRS. Economic loses are coming in two forms:

  • Immediate loss of piglets less than two weeks of age
  • Poor reproductive parameters, i.e. poor conception rates.

Aggregate percent cumulative incidence of pedv in 680 breeding herds

As chart 2 illustrates, the outbreaks in the Midwest started to increase in December, 2013, so not enough time has elapsed for more complete data to illustrate the reduced reproductive parameters.
The sudden onset of clinical signs which include sows not eating, vomiting and diarrhea in both sows and their offspring, as well as rapid death loss in young nursing piglets, are early warning signs for a sow

unit. The emotional drain that this disease has is equally troubling to the farm’s staff. Routines for the staff are immediately changed to tackle the severity of the health challenge. Managers need to examine biosecurity concerns without causing fellow employees to question each other’s activities.

Time to baseline production (ttbp) post exposure

One can only guess at the long-term issues that PEDv will create for the swine industry. The author suspects that improved biosecurity practices for all aspects of our industry will be one outcome. Our knowledge on how pathogens move throughout geographic areas will be another. A cooperative spirit in all facets of the swine industry will be needed to learn to work together for the common good when major economic challenges occur.


Tom is the owner and founder of Rensselaer Swine Services. He graduated from Purdue University with a DVM degree in 1979 and initially entered into a mixed animal practice in Illinois before moving to a mixed animal practice in Rensselaer in 1981. After several years of focusing on swine production medicine, he started Rensselaer Swine Services, P.C. in 1991. He obtained diplomate status with the American Board of Veterinary Practitioners in Swine Health and Management Specialty in 1989 and successfully was recently recertified for another term. He is a graduate of the Executive Veterinary Program from University of Illinois in 2009. Tom consults with swine operations worldwide and has been involved in the swine industry since his 4-H years on a hog and grain farm in north central Indiana. Professional involvement includes membership in the American Association of Swine Veterinarians, American Veterinary Medical Association and Indiana Veterinary Medical Association. Tom is the past president of American Association of Swine Veterinarians (AASV) and chairperson of the AASV Task Force on PCVAD from 2006 till 2009.