Since reaching U.S. soil in April 2013, porcine epidemic diarrhea (PED) virus has killed more than 10 million piglets. Numbers like these cause alarms to go up the production chain.
The swine industry has faced disease outbreaks in the past; PRRS virus began in the 1980s and Circovirus in the early 2000s, and each time the industry has learned and improved. We currently don’t know a lot about PED virus, although many studies are underway, but we do know one thing -- biosecurity was once again the break in the cycle that allowed the virus the access it needed.
Biosecurity -- in other words, excluding disease organisms from the environment -- is the most effective form of protection from disease. But, biosecurity requires a lot of effort and time, and it isn’t simple. Biosecurity efforts are tri-fold, including:
- Bio-exclusion: Bio-exclusion includes attempts to keep new disease agents out of a location (barn, farm or country) such as excluding entry or quarantine.
- Bio-management: Bio-management is managing the diseases we have through means of vaccine, timed exposure, antibiotics and sanitation.
- Bio-containment: The final, but most rarely talked about component is bio-containment, which includes management strategies that prevent disease from expanding to other locations. These strategies often have no direct financial impact on producers, but may be why PED virus spread so quickly.
“We need to look at biosecurity at all levels -- including the feed industry,” says R.B. Baker, DVM, MS, senior clinician at Iowa State University. “There has been plenty of effort there, but we discovered that they may not be as effective or compliant as needed.”
Effective biosecurity strategies for feed mills
It is suspected that the virus originally came into the U.S. from Asia in the millions of pounds of vitamins, micronutrients and other feed-related products that are imported annually. Studies have shown that PED virus can be present in feed, but where and when entry of the virus into the feed chain occurs remains an unknown factor.
While the exact origins remain a mystery, the swine industry knows one thing for sure: PED virus thrives in cold weather. As winter approaches, what can feed mills do to mitigate the risk of spreading PED virus?
Cleaning, sanitizing and disinfecting: “A lot of people miss the cleaning part -- it’s key,” says Ross Thoreson, sales manager with Best Veterinary Solutions. “You must get the surface clean to remove the dirt and organic matter and then sanitize and disinfect after that.”
The cleaning and disinfecting must be two separate steps. Concentrating on the cleaning first will heighten the effectiveness of disinfectant products.
“The PED virus is relatively easy to inactivate with disinfectants -- complete contact and enough time needs to be the focus,” says Baker. “The virus is not that tough.”
Foaming products allow for increased contact time as well as a knowledge of where a product has been applied eliminating missed areas. Reading the instructions for each product is key. A number of disinfectants now have PED virus inactivation claims.
Transmission occurs primarily by direct fecal-oral route and can be transmitted though transport vehicles, loading equipment, personnel and clothing. Ensuring delivery drivers are wearing new disposable booties and clean clothing is also recommended.
Allowing for a window: Make sure delivery trucks as well as drivers going to sites with pigs have at minimum a 72-hour window between each location. However, particularly in cold months, without proper cleaning and disinfection the window is not effective.
Heat: When feed is heated properly, the PED virus is inactivated. Baker recommends consistently heating the feed to 200 degrees to inactivate the PED virus.
Six-days rest: The virus will likely not survive in feed stored in proper drying conditions more than six days. Allowing the feed to rest, or sit, for six days or more will likely inactivate the PED virus. It is recommended that producers order their feed before their bin goes empty, allowing for the feed being delivered to rest longer.
This is a technique from the past before pseudorabies was eradicated from the U.S. It was widely recommended corn rest for 30 days in the bin before grinding into feed. This allowed drying and inactivation of the virus, says Baker.
Ingredient Sourcing: Examining where your mill is sourcing ingredients is key. Ask ingredient suppliers where they get their ingredients. Make sure they are not exposed to pigs or pig people.
While areas like China are developing regions, they do not have a focus on sourcing, which leaves the door open for containment. Know how long imported ingredients have been in the country.
Storage: Insuring feed products and ingredients are stored properly in an isolated, dry and heated environment is key to limiting contamination points. Be sure to clean, sanitize and disinfect store rooms when empty between loads. Stocking larger quantities of products so they can rest for a week or more in a heated space also reduces the risk of an infectious virus surviving.
Young swine diets: The normal pelleting process heats feed ingredients 160 to 200 degrees for less than a minute; however, young pig starter diets are pelleted at a much lower heat, increasing the chance of virus survival, if present. While feed mills are limited on their ability to increase heat at risk of losing palatability in starter diets, it’s key to ensure these ingredients are given proper care when delivered, stored and shipped to prevent contamination.
Sampling: As a way to prove to customers that the facility is PED virus-free and secure, feed mills should consider a wide range of sampling including environmental sampling, feed stuff sampling and vitamins sampling.
Nonetheless, proving a negative is difficult and requires statistically adequate sampling. A Polymerase Chain Reaction (PCR) test has been validated for PED virus, but may not be consistent when applied to feed stuffs. Thus there is increased risk that utilizing PCR technology in feed samples and ingredients can lead to false positives and false negatives.
Industry remains vigilant
The PED virus remains a large hurdle for the swine industry. Scientists still can’t grow the virus on a cell culture, so in order to show a virus is active in feed, it must be fed to a pig. This leaves many variables about where contamination could have occurred. But the fact to be concerned about is contamination is happening, somewhere.
“Right now it’s a shotgun effect -- we worry about a lot of things, but don’t have control of all of those worries,” says Baker. “Once we know where we can apply real interventions we can spend our money and time effectively.”
While some of the evidence remains unclear, the feed industry has been incriminated, and it is our turn to rise to the alarm. Prior to PED virus, biosecurity concerns had reached a sleepy lull. Now we have several research trials started, and the good news is we are learning pretty fast -- a year from now we will be able to reexamine our biosecurity processes and understand what efforts are most effective. Stay awake!