PCVAD is an acronym that you need to know.

It is the new name for what was previously called post-weaning multi-systemic wasting syndrome. The new title-- porcine circovirus associated disease—has received the U.S. pork industry’s endorsement, and more importantly that of the American Association of Swine Veterinarians. After all, AASV members are the ones who will attempt to diagnose, treat, prevent and study the disease.

The old name, more specifically the “wasting” portion, caused a lot of hand wringing among pork producers and veterinarians from a public-relations standpoint. Still, pigs dealing with the disease complex nearly do waste away.

It is important to point out up front that PCVAD is not associated with other “wasting diseases” like chronic wasting disease, which has effected the deer population. Nor is it of concern to humans; it is a swine-only disease.

Regardless of the name, the disease syndrome has been around awhile. It was first identified in 1991, in Canada, where it primarily impacted newly weaned pigs. While it was of concern, it was not devastating. Over the years, Canada, Europe and the U.S. pork industries all have dealt with variations of PCVAD.

However, the new, harsher episodes that are surfacing in Canadian and U.S. swineherds are raising the alert level. “It is making a difference on the supply of pigs in Eastern Canada,” says Clare Schlegel, Canadian Pork Council president. Ontario and Quebec produce about half of Canada’s 31 million annual market hogs.

The new version “is more severe, and is affecting older pigs,” says Bob Friendship, DVM with the University of Guelph in Guelph, Ontario. “It looks like a different kind of disease than we have had in the past.”

Europe faced the new version first, which is why it’s often referred to as the European strain. It surfaced in Canada’s eastern provinces of Ontario and Quebec in late fall 2004.

“It’s now widespread in North Carolina, the Midwest and as far west at Arizona,” notes Richard Hesse, virologist with Intervet.

What’s Old is New

Producers hate to hear this, and veterinarians hate to say it, but there are still a lot of unknowns about PCVAD, especially the new challenger.

First, let’s review the “old” version. Clinical signs include progressive weight loss, jaundice, diarrhea and respiratory distress, in weaned pigs (6 to 10 weeks old). Hepatitis, nephritis and pneumonia can occur. The lymph nodes become both enlarged and depleted, which compromises the immune system. Internal organs, such as the liver, kidney, pancreas, lungs, heart muscle and parts of the intestinal tract are often affected. Lesions are commonly found in post-mortem exams.

PCVAD is actually a disease complex, which requires multiple components to develop. For example, circovirus type-2 (PCV-2) is increasingly recognized as a factor, but its presence doesn’t automatically equal PCVAD. For that to occur, other infections such as porcine reproductive and respiratory syndrome, swine influenza virus and Mycoplasmal pneumonia often need to enter the picture. Environmental stressors add to the potential as well.

Concerning the “new” version, many of the symptoms are similar to the “old” version. The significant difference is that it affects older pigs— those weighing 90 to 150 pounds.

In the first week or two of PCVAD developing, you might see a little diarrhea due to Lawsonia infection. “It can be confused with ileitis,” notes John Kolb, DVM, technical services veterinarian with Boehringer Ingelheim Vetmedica, “both in the live animal and in post-mortem exams.”

By the third or forth week, pigs start to look tough. “Pigs don’t eat well, which leads to the physical decline,” says Joe Connor, DVM, Carthage Veterinary Clinic, Carthage, Ill. 

Kolb points out, as the diarrhea fades away, respiratory issues surface. The active, clinical infection period tends to last about 5 weeks.

Mortality rates run 18 percent to 50 percent. “We’ve had reports of 70 percent,” notes Hesse.

Even after you step in with management interventions, the impact can linger. “A herd with a 3 percent mortality, might jump to 15 percent, then drop back but still deal with 8 percent mortality,” adds Connor.

A 6- to 7-month period with 20 percent mortality in a unit is not uncommon. Winter months are worse than summer, notes Kolb.

Morbidity rates run from 4 percent to 30 percent, with episodes pushing beyond 50 percent, according to Joaquim Segales, DVM, Barcelona, Spain.

Some pigs recover within 3 to 6 weeks. They eventually gain weight and look normal. “Without records, you wouldn’t know the group was affected,” says Connor.  “But the recovered pigs often still have enlarged lymph nodes.”

Spreading it Around

Specific to PCV-2, the current thinking is that the virus is spread through nasal and fecal shedding. That process can last 70 days or more, according to Hesse. “Viremia can last 6 weeks or more; we don’t know when it stops.”

It appears that it doesn’t take much of an oral PCV-2 dose to infect pigs, so minimizing the viral load is key to controlling PCVAD. “This is a tough-as-nails virus,” says Hesse. “Horizontal transmission is the predominant mode of transmission; it is an extremely mobile virus.”

Specific to PCVAD, there is tremendous barn-by-barn variation, as well as variation within a pig group. Why some animals are affected and others are not is still unknown. “Studies suggest there may be some genetic robustness,” says Connor.

Diagnosing PCVAD is a challenge for veterinarians because the signs can point to any number of health issues. PCR tests, immunohistochemistry, histological lesions and clinical history are used together to confirm the diagnosis. “Real-time PCR is new and can quantify the viral load,” says Hesse. So that’s a useful tool.

One consensus to PCVAD control or prevention is not to overcrowd pigs. Moving, resorting and mixing pigs is another form of roulette. Washing and disinfecting facilities are standard-operating procedures, but most importantly—let them dry thoroughly. If PCVAD surfaces in a group, remove the severely affected pigs. For other guidance, see “Steps to Take Today” on page 16.

Fort Dodge Animal Health has received approval for a PCV-2 vaccine for use in the United States on 4-week-old pigs or older. Other companies are working on products for release sometime this year.

Addressing PCV-2, can help put out the PCVAD fire; as can addressing other co-infection factors.

But let’s face it, with double-digit mortality rates in the finisher, any answers and ideas to help address PCVAD can’t come quickly enough.


Looking for Answers

Various segments of the swine-health field are scrambling to find answers to porcine circovirus associated disease.

The American Association of Swine Veterinarians has partnered with the Purdue University Regional Visual Analytic Center to develop a tool to promote a better understanding of the syndrome.

“The tool will facilitate geographical and temporal visualization of disease syndromes and potential risk factors,” notes Sandy Amass, DVM, PurdueUniversity.

PURVAC currently uses similar tools to monitor human-health challenges and will design one for the pork industry at no cost. But, real-world data is needed to accomplish this task. Therefore, AASV is asking members to complete a survey for cases of elevated mortality. All data collected will remain confidential. The information submitted will not be made public and cannot be accessed using the Freedom of Information Act. The only people that will see the raw data will be designated AASV representatives and the Purdue Project Team.

Veterinarians can get more information at www.AASV.org

Also lending a hand is Boehringer Ingelheim Vetmedica, which will fund research targeted at improving the diagnosis, control, prevention or eradication of PCVAD. Beginning this year, the company will award a total of $75,000 annually to three North American research projects. The awards will be based on the review of submitted proposals. Emphasis will be placed on a one-year completion timeline and real-world application. 

Proposals for this year’s awards are due Aug. 15. The three proposals selected for funding will be announced at the 2006 Leman Conference this September.

More information is available at http://www.PCVADresearch.com