Tackling PEDv with feedback programs

As the PED virus continues to spread, producers around the world are employing a variety of control tactics. What can we learn from their experiences, and should feedback programs be part of the strategy?

Isselee I Dreamstime.com | Creating immunity in sows is essential during a viral disease outbreak.
Isselee I Dreamstime.com | Creating immunity in sows is essential during a viral disease outbreak.

Porcine epidemic diarrhea (PED) virus is a coronavirus that causes severe diarrhea and dehydration. It is spreading throughout the U.S., Canada and Asia. Up to 100 percent morbidity is seen, resulting in a significant economic cost to the industry. With producers having little or no warning of their pigs becoming infected, they have to think on their feet to minimize losses. There is between 80 and 100 percent mortality in young piglets during an outbreak, with productivity of the whole herd affected.

Creating immunity within the herd quickly is key to dealing with an outbreak. Feedback programs, which transmit the virus in a controlled way throughout the unit, are becoming popular. The benefit to pregnant sows, in particular, is that within two to four weeks natural immunity is created, which can be passed to the piglets via colostrum.

Producers can't afford to ignore biosecurity at this time, and extra precautions should be taken to help prevent the spread of the virus.

What is a feedback program?

A feedback program is a way of homogenizing herd immunity by "feeding" material containing the pathogenic agent. "This method had lost favor in recent years, until the PED virus entered the U.S. in April 2013," said Butch Baker, a senior clinician at Iowa State University. Historically, it has been used to prevent the spread of diseases including transmissible gastroenteritis virus (TGE) and piglet scours caused by E. coli, Clostridia, etc. In these instances, fecal material is fed back to the breeding herd. Also, in the case of PED virus, the aim is to eliminate the virus from the farm and back-feeding is carried out for approximately 10 days, during an outbreak.

Feedback programs have also been used to control parvovirus, reproductive failure and shaker pig syndrome. Placental material and stillborn piglets (mummies) are used as the feedback material; in the case of shaker pig mixture, a mixture of fecal and mummy is used. Ongoing control methods for problems like colibacillosis also employ feedback programs. In practical terms, diarrhea is collected from the farrowing house and mixed with water and fed back to sows and gilts for several weeks before farrowing. "The aim is to increase lactogenic immunity and antibody absorption from the colostrum," stated Baker.

What to back-feed?

There are conflicting opinions as to whether it is best to use dead piglets or fecal material. In the past, the intestines of dead, sick pigs were used to expose the breeding herd, and vets are advising it during PED outbreaks. Baker argued that "in my experience, it isn't necessary to use dead piglets as there is more than enough virus in the diarrhea from the environment." Michele Pfannenstiel, CEO of Dirigo Quality Meats, commented on the potential food safety risks and spread of disease when feeding pigs back to pigs. Within the EU, this practice was banned as part of the Waste Feeding Order, put in place after the BSE crisis. However, fecal feedback material is allowed and is used as a way of exposing young gilts to farm pathogens.

The use of farm-specific vaccines to create immunity to a variety of health challenges is becoming more common. The small intestine of diseased piglets are dissected and frozen before being sent to institutes for vaccine production, removing the risk of back-feeding this material. "The drawback of back-feeding is that eventually immunity will fall," says Alexander Dolzhenko, drawing on his experiences as production director of a large Russian pig producer. In his opinion, it can only be effectively maintained through vaccination of both sows and rearing pigs. "When we stopped vaccinating, although we carried on back-feeding (with fecal material), we took bloods from sows and found low levels of immunity to the virus," Dolzhenko stated.

Vaccines for PED are being developed but are not available in all regions. Vaccines made from killed or modified PED viruses have been used in China for several years, but there are concerns over their safety and efficacy. In the U.S., specific PED virus genes, which produce immunity in the host, have been replicated and used as vaccines.


Whilst feedback programs are proving to be a useful tool in fight against PED, they won't work in isolation. Biosecurity plays a vital role in preventing the spread of the virus both between and within farms. The transmission route for PED virus is fecal-oral; it is therefore essential to ensure that anyone or anything arriving at a farm does not bring in infective material. This means animals, people, equipment and vehicles. "Smaller herds are particularly at risk", said Pfannenstiel. "They need to take a proactive approach and think about truck movements, particularly from auctions, etc."

In the U.S. and Canada, the unusually cold weather may have helped the virus spread, reducing animals resistance and hampering biosecurity. Although the virus is susceptible to disinfectants, they don't work well in freezing temperatures. The addition of anti-freeze is suggested to prevent the disinfectant freezing and allow the necessary contact time.

Staff moving between barns should use gloves, shoe covers and consider changing clothes. Particular attention needs to be paid to the cleaning of housing and equipment, to help prevent the virus spreading. If a farm becomes infected, a 90-day closure and deep clean is recommended.


It is well known that stress has a negative effect on immunity. During an outbreak, it is pertinent to delay procedures such as tail docking and teeth trimming. Dead piglets should be removed quickly, along with those that are very unwell. There is much debate as to whether it is worth trying to nurse sick piglets. Many argue that the cost of such interventions is not worthwhile. However, particularly on family farms, not to try to save animals goes against their ethos.

As dehydration is the main cause of death, providing an electrolyte solution is important. The use of calf-type milk replacer to provide nutrition has also been recommended. Some vets have seen high survival rates on infected farms, when piglets are weaned at 5 days; younger piglets are not likely to survive. However, Baker explained that "there appear to be two strains of PED virus, one much less virulent than the other." This would explain why early mortality and therapy survival rates vary.

Go on the attack!

Feedback programs help to build immunity to disease challenges within herds. However, a variety of strategies can help to prevent disease outbreaks. Biosecurity procedures should be followed to the letter. Transport is a big risk factor; limiting movements and disinfecting correctly is vital. "Good nutrition and overall health status are important in enabling pigs to fight of infection," Pfannenstiel reiterated.

Whether there has been a serious outbreak in their country or not, pig producers across the world need to be vigilant. To quote Canadian pig farmer John Vandorp, "I am learning just like everyone else...so sharing what works is very important." Whilst prevention is, as always, better than a cure, in the case of PED it seems that going on the attack is what is needed. Feedback programs are a successful control tactic during viral outbreaks like PED.

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