US pig industry battling PEDV spread

Porcine epidemic disease virus (PEDV), a disease fatal tonewborn piglets is spreading through the US since its arrival in April 2013.

Neonatal pigs are most susceptible to PEDV infection.
Neonatal pigs are most susceptible to PEDV infection.

Porcine epidemic disease virus (PEDV), a disease fatal to newborn piglets and unfamiliar in the United States, is spreading through the Midwest an alarming rate with 300 confirmed cases in 16 states, since its arrival in April 2013. PEDV has been in the global pig industry for decades, with reports from Great Britain in 1972 and from China in 1982. Yet, with no previous exposure in the US, PEDV poses an economic threat to the 68,300 hog farms that make up the US pig herd.

PEDV affects a pig's intestinal system prohibiting the cells from absorbing the nutrients and fluid in water and milk, thus severely dehydrating affected pigs. While older pigs tend to recover in two to four days, entire populations of neonatal piglets are being wiped out. With no immunity to the virus available from sow's colostrum, piglets three weeks and younger have no resistance to the strain and lack the reserves necessary to recover, resulting in an 80 to 100 percent mortality rate. 

Who is at risk?

The entire US pig herd is naĂŻve to PEDV and thus, highly susceptible to infection. Farrow-to-finish operations experience the most severe impact with exceptionally high piglet mortality. However, the number of positive cases is highest in grow-finish operations. This may be linked to improperly cleaned trucks used to haul pigs from the farm to the slaughterhouse. 

Trucks that are not properly sanitized between loads can easily pick up the virus at the slaughterhouse and spread it among farms. With PEDV being a fecal-oral virus -- that is, it is transmitted by pigs ingesting manure -- it can be introduced through human traffic, feed, contaminated trucks, trailers and equipment. The virus is not harmful for other animals or humans, and meat from PEDV infected pigs is safe for human consumption.

Biosecurity measures

It is unknown how the virus arrived in the US. Multiple cases of PEDV were confirmed around the same time in various pig farms across the country. Three weeks after the first confirmed breakout, the National Pork Board approved $450,000 to be used for PEDV research. Researchers are looking for answers on how to contain and eliminate the virus. It is currently unknown how long an infected pig is contagious, and how long PEDV is able to live outside its host on clothing, equipment or feed.

Until more is learned about PEDV, the first step in prevention is tightening biosecurity. Pig producers are advised to keep a log of who visits their facilities and to limit the amount of traffic from vehicles and personnel on the farm. The goal of the hog industry is to prevent PEDV from being added to the list of US swine pathogens. 

To succeed, infected farms need to contain the virus until it can be eliminated from their herd. Trucks should be properly sanitized between farm visits with warm water and a disinfectant. PEDV is susceptible to most disinfectants that contain an agent for destroying viruses.

Internal  biosecurity 

Enforcing internal biosecurity measures are equally important for pig operations with more than one barn and multiple sites. If one barn on an operation is infected with PEDV, extra precautions are taken to ensure the virus doesn't spread to the rest of the facilities on the farm. 

Moving pigs in an all-in/all-out operation is advised to prevent mixing contagious pigs with an unexposed group. Employees, visitors and veterinarians must change boots and coveralls between barn visits. Power washers and other equipment are to be thoroughly sanitized with virucidal sanitizers from top-to-bottom between in-building uses. 

PEDV diagnosis

The virus responsible for PEDV was originally thought to be the same as that of transmissible gastroenteritis (TGE). The PEDV and TGE viruses are from the same coronavirus family and share the same clinical signs: diarrhea and vomiting, loss of appetite, severe dehydration and a decrease in milk supply from lactating sows. 

Because the clinical signs are similar for both viruses, the only way to diagnose PEDV is through a laboratory test. Lab tests can be done with a fecal sample, a rectal swab, feedback material or an environmental swab. PEDV and TGE immunity are not able to cross-protect against each other; that is, vaccines for the TGE virus will not protect pig herds against the PEDV virus, and herds that have been exposed to TGE virus do not have immunity to the PEDV virus.

Eliminating PEDV

While vaccines and immunity to the TGE virus will not protect herds from the PEDV virus, there is reason to believe that the same procedures for eliminating TGE will work to eliminate PEDV, with a few exceptions. The TGE virus is deactivated in warm weather. However, the spread of PEDV in warmer climates in the US has proven this strain is more stable than its counterpart and is surviving in heat waves of 85 degrees F or higher. Still, the US pig industry hopes the rapid spreading of the PEDV will slow down or stop during this summer.

The following four procedures are recommended for PEDV elimination:

1. Close the herd 

Pig producers are advised to begin a strict 12-week procedure of elimination with their veterinarian as soon as a confirmed case of the PEDV is diagnosed in their herd. The procedure begins with closing the herd -- not allowing new pigs to enter or leave the infected population.

If replacement pigs need to be added at a later date that is within the 12-week period, they should be added to the infected herd right away. During the first three weeks, the entire herd is aggressively exposed to the virus by placing infected pigs nose-to-nose with the rest of the herd and spreading around infected feces. It's vital to monitor each pig and make sure the virus is caught and pigs are showing clinical signs.

2. Sanitize the facility thoroughly 

Approximately after three to four weeks of aggressive exposure, when clinical symptoms have stopped, the herd is moved out of the infected facility in an all-in/all-out movement -- every pig is moved out at the same time. The infected facility is then properly sanitized with warm water and a virucidal sanitizer and dried completely before allowing pigs back into the pens.

3. Add sentinel pigs 

Thirty days after clinical symptoms subside start adding sentinel pigs to each pen of the closed herd. As the herd builds immunity to PEDV, the clinical signs will decrease. Therefore it is necessary to add pigs to the herd that have never been exposed to PEDV to see if they stay negative. After 30 days, if the sentinel pigs do not show clinical signs of PEDV, then the virus has been successfully eliminated from the herd.

4. Build pregnant sow immunity 

Infected farms with pregnant sows should expose the sows as early as possible to infected fecal matter to ensure the sow catches the virus and builds immunity to PEDV before farrowing. After three weeks, the sow will have built an immunity that is passed through her colostrum to her piglets resulting in fewer deaths. 

The elimination procedure is not risk-free. Other pathogens from sentinel pigs can be spread during this process, and the herd can be infected with a different virus. All steps in the procedure should be done with precaution. 

Sentinel pigs that are brought in from other sites or farms should be quarantined for 30 days in a separate facility that is at least 500 yards from the rest of the facilities. While the US pig industry is optimistic that strict elimination procedures and biosecurity will help to contain the virus, they are wary of the risks involved and concerned with discovering how PEDV entered the US.

Page 1 of 55
Next Page