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New Weapons Now Available for the War Against Circovirus Type 2 (PMWS)

by 5m Editor
1 April 2006, at 12:00am

CANADA - Farm-Scape: Episode 2103. Farm-Scape is a Wonderworks Canada production and is distributed courtesy of Manitoba Pork Council and Sask Pork.

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Farm-Scape, Episode 2103

New vaccines are offering new cause for optimism as swine producers worldwide defend their herds against a disease that afflicts baby pigs, just after they leave their mothers.

Post-weaning Multisystemic Wasting Syndrome (PMWS) was the main focus earlier this week in Saskatoon as swine producers gathered for the Prairie Swine Centre's annual "Focus on the Future" conference. This new infection is believed to actually date back as far as 1991; it affects young pigs, typically from eight to 16 weeks of age and it is often fatal.

Disease Characterized Just Over One Decade Ago

“The name PMWS abbreviated was coined back in ’95 by [Dr.] Ted Clark and [Dr.] John Harding," recalls Dr. Frank Marshal, with Camrose, Alberta based Marshal Swine Health Services, part of the Western Swine health Associates.

“It’s a descriptive term, for what the disease plays out in our farms. It’s post weaning, so after weaning, multi systemic wasting. What this means is that you can have multiple systems within the body affected so I could have lung, liver, kidney, skin or any organ or tissue affected and consequently producing a wasting syndrome in the animal.”

Dr. John Harding, an associate professor of swine production at the Western College of Veterinary Medicine notes, “This is an emerging viral disease. It was discovered in western Canada in 1995, [and] has spread throughout the world since then. [To] most European, Asian countries in the decade since. It has come back to Canada and is affecting Ontario and Quebec at this point in time and causing some fairly severe mortality on some of the affected farms.”

Circovirus Type 2 Considered Primary Cause

The primary cause has been shown to be a common pathogen, porcine circovirus type 2 (PCV-2). However, because this organism is so common, it is believed some additional triggering mechanism is required for the infection to result in actual symptoms.

“The cause of this disease has been extensively debated over the last decade. What we do know is that a new virus called circovirus is required to cause the disease but there are other factors that are also required as well and they work synergistically,” explains Dr. Harding.

“Ones that we certainly know of are other infections and those would be probably the biggest ones affecting us today, so other infections like PRRS virus, swine influenza virus, parvovirus have been shown experimentally and on the field as being triggering factors,” he says.

Dr. Marshall notes, “The virus itself has been shown to produce this scenario just by itself. However, out in the field we see the scenario that you require another cofactor, another disease entity to be cycling at the same time. In this way it up regulates the immune system stimulating it to combat disease X, Y or Z. If circovirus is present at this time and cycling, you will get PMWS as a consequence.”

“We know there’s cofactors involved, various viruses, bacteria, mycoplasma agents, those things will be at play when PMWS causes major mortality.”

Symptoms Can Be Devastating

The one factor that leaves no room for debate is the impact of this syndrome on inflicted animals.

“The big one is obviously mortality, so elevated mortality either two to four times pre-outbreak levels and that can affect finisher pigs,” Dr. Harding observes.

“It just depends on the farm and the situation,” he adds. “So mortality is obviously the big one but, in addition to that, it will cause slower growth rates so producers may see more pigs not getting to weight in time and have to hit some sort of pre-market cull type grid. Then, as well, there’s probably an affect on feed conversion on the farm as well.”

Management Remains the Front Line of Defense

Until recently the only defense against PMWS was management. Dr. Marshall recommends, “Really staying on top of their herd biosecurity, so that is to prevent introduction of other diseases, new diseases into the herd.”

He explains, “Some of our swine diseases move through aerosol means. That’s through the air, so radiuses around a farm, if it were two to three miles, we’re protected from some diseases but not others. There’s another virus that’s emerged almost 20 years ago now, PRRS virus. This one will move as an aerosol two to five miles very readily, as well as direct pig contact. So we really want to focus on preventing other diseases from establishing within a herd and/or if they are in a herd you look to eradicate them or control them and stabilize things so you avoid having these viruses cycle when circovirus is cycling.”

Now, new vaccines are offering new reason for optimism. Four companies have either introduced or are on the verge of introducing new products.

One of those companies is Merial. Merial was granted a special import permit last month clearing the way for the distribution in Canada of Circovac, a product that is administered to the sow which then passes the protection to her offspring.

Merial Introduces Circovac to Canada

Dr. Francois Joisel, Merial’s global technical services director was on hand during the conference to explain to those on hand how the new product works, to outline its development and to provide updates on the level of infection in Europe.

“This is a sow and gilt vaccine,” he explains. “This is an inactivated vaccine which is intended to be used before farrowing to increase passive immunity for the piglets.”

“We have decided to choose the sow option for this vaccine because, first of all, contamination of the piglet occurs very early in the life. Second it’s really necessary not to immunostimulate the piglets early in life because it may trigger PMWS so the sow option appeared to be the best option.”

Dr. Joisel notes the vaccine has undergone considerable laboratory experimentation and the progeny of vaccinated gilts were perfectly protected. “We have been using it for one and a half years in France and Germany and now we have more or less 350 thousand sows that have been vaccinated and the results are particularly encouraging.”

Jean-Claude Noel, Merial Canada’s product manager, continues, “The vaccine called Circovac against PCV2 has been researched for at least the last ten years. Merial has been looking at what’s going on in the field of PCV2.”

He says, “PCV2 and PMWS have been present in Europe for at least the last eight years. We saw probably a smaller number of mortality when we’re talking about mortality here [in Canada] ranging in the ten to 15 to 20 percent. What we saw in Europe was more in the, I would say, eight to ten percent mortality rate.”

The strain of PCV2 used to develop the vaccine actually originated in western Canada but the vaccine has been effective in Europe, and because the strain currently being reported in Quebec and Ontario is believed to have originated in France, the vaccine is expected to be effective against that outbreak.

Strict Conditions Apply to Distribution

Because the product is not yet fully registered in Canada, there are certain restrictions that apply.

Noel explains, “Canadian regulations are fairly rigid and I would say it’s good for the Canadian market to be like that so we went to a special demand because the product is produced in Europe. We had to ask for a special permit from the Canadian government.”

“It was granted to us this year in February so we can import the product that is produced in Leone in France and that is the same product that is used in Europe right now.”

He says, “After consulting with the government we decided to put in a kind of a way of ordering the product. It has to go through a veterinarian first. The veterinarian has to agree to follow the rules of the government for this special permit.”

He adds, “The veterinarian is sending the demand to the office of Merial Canada and after that he can send orders and order the product.”

Demand for Circovac in Canada Already Brisk

Although Circovac has only been available for a couple of weeks, Noel notes, “We received demands from veterinarians across the country, since the disease is not present only in the east.”

Nonetheless, he remains confident availability of the vaccine will be sufficient to keep up with demand. “It seems that, in terms of supply, were going to be OK. The production in Leone is sufficient right now for France, Germany, Denmark and we are one of the countries that receives product from Leone.”

Other New Vaccines Offer Additional Hope

Dr. Harding concedes, “Vaccine is really what we’re all holding onto as being the silver bullet and we’ll see. Time will tell whether it is the silver bullet in Canada.”

He adds, “There are four companies that have products that are approaching market at this point in time. Two companies have an emergency license for products.”

But, he notes, “One company has inventory in the country at this point in time and it’s starting to filter out to farms.”

He adds, “[Depending on the vaccine] vaccinations are either given to sows before farrowing or they’re given to piglets some time in the suckling or early nursery phase.”

Management Still First and Best Defense

Despite the introduction of the new vaccines, the basic principles of good management remain the first line of defense against this and any other livestock disease.

“We’ve continued to tackle all the issues around disease stabilization in the sow herd, getting back to the basics of animal husbandry and management, focusing on all the issues around biosecurity, sanitation,” explains Dr. Marshall.

“All of those things have in depth review on each of the farms that are dealing with it. It’s like going to war, if you like. You set up all your strategies and slowly work away at getting that done.”

Staff Farmscape.Ca

5m Editor