Swine disease due for a checkup

Friday, August 19, 2022

By Geoff Geddes

Swine disease is like income tax: unpleasant to think about but ignore it at your peril. For producers, such conditions are expensive, disruptive and damaging - and they're no picnic for the pigs. In combatting the problem, it helps to know where things stand with prevalent diseases and where they might be heading in the years to come.

"In general, disease is a significant challenge within the pork sector in terms of animal health and welfare, production and profitability," says Dr. Egan Brockhoff, veterinarian with Prairie Livestock Veterinarians in Red Deer, Alta.

While the industry tries to put a price tag on disease, it's not as simple as it sounds.

Pay me now & pay me later

"I've seen PRRS (porcine reproductive and respiratory syndrome) impact estimated at anywhere from $4 to $15 per pig and Mycoplasma in the $5 to $8 range," says Brockhoff. "It really depends on the variant of a particular disease and on which costs you're considering."

While there's immediate fallout in the form of mortality or morbidity, there are also long-term costs such as lower productivity, ongoing damage to the breeding herd and reduced fertility. Whether it's short-term or big picture, the impact can be equally devastating.

"I've worked with outbreaks where all the gilts had so much damage to their respiratory tract and scars from chronic pneumonia that it affected them for the rest of their lives," says Brockhoff. "Diseases like PRRS can destroy a farm's financial viability forever. On the other hand, PED (porcine epidemic diarrhea) causes fewer ripples in the pond down the road, but it can bring massive costs when it first appears."

PRRS

"PRRS has been at the forefront of pig diseases since the late 1980s," says Dr. Kevin Vilaca, veterinarian with South West Vets in Listowel, Ont. "It can cause abortion issues and affect sperm production in boars, but also has that respiratory component that leads to lung damage in growing pigs. All told, it's the most significant and expensive disease for the swine industry."

Though vaccines have shown some promise against PRRS, its high mutation rate makes it hard for science to keep up. As a result, strong biosecurity is the best bet for keeping it at bay, especially in winter.

"PRRS likes to move around a lot and thrives in cold conditions," says Vilaca. "It's started with a vengeance this winter and we're seeing a real upswing of cases in Ontario. From what I'm hearing, that is also the case throughout North America right now."

Between its mutations and mobility, PRRS poses a real challenge for veterinarians.

"We seem to get a new strain of PRRS every five to seven years," says Brockhoff. "It moves in many different ways: via live pigs, semen, trucks and feed and is also truly aerosolized, so it moves through the air."

PED

Originating in China, PED came to Canada in 2016, first arriving in Ontario via feed ingredients. Like PRRS, PED does well in cold weather and can move easily into barns in a variety of ways.

"The silver lining with PED is that it really exposed our weaknesses when it comes to biosecurity and demonstrated how important it is to maintain good practices in that regard," says Vilaca.

For the most part, Canada has done well in controlling the spread of PED, often containing and eliminating it quickly when it becomes present on-farm.

"The notices going out from provincial pork bodies have been very helpful in sharing where PED has been found most recently and what your risk level may be," says Vilaca. "Since it's not airborne, PED is easier to prevent than something like PRRS, but the fact that it causes almost 100 per cent mortality in piglets makes it very expensive when it does take hold."

PED is in the headlines again after affecting more than two dozen herds in Manitoba, so there is still work to do in addressing the virus.

"We don't have any really successful vaccine options for PED," says Brockhoff. "Also, once animals are affected by it, they only stay immune for four to six months and can get sick again with subsequent exposure."

Influenza

Due partly to its airborne nature, influenza has posed a problem for the swine industry, but that may be changing.

"In 2016, we started looking at influenza differently," says Vilaca. "The human model for dealing with the virus works very well and vaccines for people have been a marvel of public health. Every year, the World Health Organization sets up surveillance across the globe to identify the high-risk influenzas and manufacture vaccines to combat them. It begs the question: Why can't we do something similar for pigs?"

Since South West Vets deals with 80 per cent of swine in Ontario, they approached the Canadian Food Inspection Agency and proposed a regional vaccine for swine influenza. Finding a receptive audience, they set up a database where they could track cases of the disease and any changes they saw in the field.

"We've built the first regional database for swine influenza in Canada and it's already proving highly successful in helping to properly vaccinate herds and reduce the impact of the disease," says Vilaca.

In response, other provinces are now looking at creating a similar model.

Type 2 porcine circovirus

Though the original porcine circovirus has been around for decades, vets and producers began seeing the type 2 species, a more virulent strain, on farms in 2004. Spreading quickly, it soon appeared in most North American pork farms and became the dominant virus on the continent.

"Its main function is to suppress the immune system and it's really variable in its impact," says Vilaca. "Some infected animals remain quite healthy, while others get very sick. It also tends to hide out in the immune system, making it harder to track."

Fortunately for the industry, European scientists recently released a vaccine that has largely eliminated the threat. On the downside, producers are now dealing with an unwanted sequel: porcine circovirus type 3 (PCV3). In the last couple of years, PCV3 has been playing a greater role, acting as a primary cause of disease in combination with other viruses.

"Our understanding of PCV3 is a bit lacking, but we now have some ability to make vaccines," says Vilaca.

"Farmers are having mixed results with the vaccine, so we need to work with researchers on better strategies to control PCV3 or prevent it altogether."

Rotavirus

Science has identified eight different strains of rotavirus in pigs, with serogroup A being the most prevalent. The virus is widespread and while most pigs develop immunity and rarely show clinical signs, they can become silent carriers and shed the virus to their pen mates.

"We have rotavirus type A, B and C in Canada," says Brockhoff. "They're a constant, nagging problem that causes piglet and nursery scours, yet we don't have an effective vaccine against all three types, so this is a tough one."

African swine fever (ASF)

As a disease with almost a 100 per cent mortality rate, ASF continues to draw attention since its emergence in China and subsequent movement through Europe via wild pig populations.

"This is a border-closing disease in the U.S. or Canada," says Vilaca. "Our country exports 70 per cent of pig production, which means we couldn't eat our way out of that much pork. It's now a notifiable disease in Canada, so any signs must be reported immediately to the government."

Stay afloat: stay informed

Between new, emerging diseases and ones that keep reappearing as a different strain, the pork sector has its hands full in combating them. As with any battle, getting an edge may start with a key step: knowing your enemy.

"Some of the most important tools we have are the Canadian Pork Council, Canadian Association of Swine Veterinarians and Canadian Animal Health Survey Network (part of the Canadian Swine Health Intelligence Network (CSHIN))," says Brockhoff. "They're all about keeping vets and producers informed of health changes."

CSHIN gets most of its data from regional networks like the Canadian Western Swine Health Intelligence Network and Swine Health Ontario. All of these groups provide regional updates to the industry on what's happening in the area.

What you don't know CAN hurt you

"It's all about knowledge transfer and raising awareness of what's working and what's not," says Brockhoff. "We also work closely with our American colleagues and their surveillance efforts to broaden our knowledge."

As important as these organizations have become, producers themselves play a large role in disease prevention.

"I tell my clients to stay informed and make sure they're talking to their vet regularly about what is happening around them," says Brockhoff. "From there, it comes down to three things: biosecurity, biosecurity and biosecurity. We may not fully understand swine disease, but we know that it's never random. When we look at biosecurity audits and surveys, there's always room for improvement."

When biosecurity seems like BS

At the same time, veterinarians recognize the threat of biosecurity fatigue for producers dealing with the prospect of disease daily.

"People are tired of always showering in and out; biosecurity is hard work," says Brockhoff. "They just want to go about their business and do their thing, which is why we're always conducting research on biosecurity. How do we make protocols simpler to follow? How can we engage everyone on the farm to invest in biosecurity? There's no silver bullet, but we have to do what we can."

High hopes for high-tech

As with many sectors, advances in technology are another weapon in the fight against disease.

"It's exciting to see what the future holds," says Vilaca. "Technology has allowed us to better understand some of these complex disease interactions. We're now more equipped to detect disease earlier, determine if it has mutated and decide whether a vaccine is applicable. We can get a clearer picture of what's happening with our herds. Is a certain disease present? What is it doing and how can we distinguish between a virulent strain and one that's less threatening?"

Many years ago, science could only state if a disease like PRRS was present on a farm. Fast forward to 2021, and we can now determine the extent of disease.

"Science builds on itself and every bit of information we gain is progress," says Vilaca. "We have advanced to the point where we can identify the different types or strains of a disease and see if and how it's changing in the field."

Genes that fit the problem

Thanks to genetic sequencing, researchers may also get a fingerprint of a virus and calculate the percentage change in its mutation.

"We look back 20 years now and say, ‘Can you believe we used to make decisions off of that?'," says Vilaca. "At the time, though, it was the best information we had. Two decades ago, I couldn't do what we're doing now with influenza, as we couldn't interpret genetic sequence technology and understand where the key disease sites are located. A lot of that knowledge has been acquired from research on human influenza and it's truly a game-changer."

For many in the pork industry, progress on the disease research front can't come too soon.

"One constant for our sector is the appearance of new and reemerging diseases," says Brockhoff.

"Twenty years ago, PRRS first came on the scene and a decade later it was porcine circovirus. There may be an old virus that has stayed quiet for some time and then suddenly changes and becomes significant in a hurry.

"I've seen a lot of new threats over my lifetime, and while we don't have 200 years of good data to say for sure that the cycle is speeding up, it doesn't feel as if it's slowing down. With the growing trend of globalization and an increase in pig movement, there will always be new challenges for us to address." BP