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Wild pig problem in the spotlight at pork conference

The number of feral pigs is growing here and playing a key role in the African swine fever epidemic elsewhere

(Editor’s note: The following is an abridged and edited version of two articles. The full versions can be found at meristem.com by clicking on the 2020 Banff Pork Seminar link.)

Two presentations at the 2020 Banff Pork Seminar highlighted the threat posed by wild boars.

Ryan Brook, a University of Saskatchewan associate professor and wildlife researcher, told seminar attendees that wild pigs are an ecological disaster, the problem is exploding and time is quickly running out on the ability to eradicate the problem.

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In addition, an international expert on African swine fever spoke of the key role that wild boars have played in this devastating epidemic.

Unrecognized problem

“More than 700 delegates came here to talk about managing pigs inside the fence,” Brook said in his address. “I’m the only one who came here to talk pigs outside the fence.”

The problem started in the ’80s when animals escaped from wild boar farms or were released into the wild as the economics of that industry faltered. Since then, they have bred with domestic pigs, resulting in larger animals (some weighing several hundred pounds) and larger litters.

In the wild, these animals travel in groups called ‘sounders’ run by a matriarch female with lone males travelling extensively in search of females.

Wild pigs are incredibly smart and elusive, and populations here are growing because they’re so successful in finding food, said Brook. There are many myths about wild pig control, he added, with one of the biggest being that populations can be controlled by sport hunting.

“We will not barbecue out this problem,” he said. “If anything, sport hunting increases the problem. Wild pigs scatter and more groups are formed as a result.”

Brook’s wild pig research efforts are funded in large part by the United States Department of Agriculture with support slowly growing from Canadian partners. But the problem is largely ignored here, he said.

“A year ago I thought African swine fever would have driven a whole new level of renewed interest in the wild pig problem,” said Brook.

But interest and support for control methods and research have not really increased, he said.

Role in African swine fever

African swine fever has made headlines around the world and controlling it will be extremely challenging — in part because of wild boar populations, said Klaus Depner, a virology expert from Germany’s Friedrich-Loeffler-Institute and a leading authority on the disease.

He detailed the history of African swine fever, which until a dozen years ago was considered a so-called exotic disease with minor impact. That changed when an epidemic started in Georgia in 2007, subsequently spread throughout the Caucasus and the Russian Federation, and then into the European Union in 2014. Four years later the first outbreaks were reported in Asia and it has since devastated China’s sow herd.

The strain in the current epidemic is highly virulent and can result in 90 per cent (or more) of an infected herd dying. However, it is not as highly contagious as first

thought and analyses of domestic pig outbreaks have found its contagiosity (degree of contagiousness) is rather low.

This complicates early disease detection because at the beginning of an outbreak usually only a few pigs are affected and die.

This is one factor in what Depner calls “the persistency triangle” — low contagiosity prevents fast and complete depletion of the host population, high case fatality makes the virus largely available in the form of carcasses, and high tenacity (the ability of the virus to survive over a long period) ensures its long-term persistence in the environment.

This has resulted in the disease becoming endemic in the wild boar populations of several European countries.

When African swine fever first reached the EU, it was expected to either spread rapidly within the wild boar population or fade out due to high case fatality rate and the resulting absence of long-term carriers. But none of these predictions held true. The infection survived locally in the wild boar population independently from outbreaks in domestic pigs.

It is now believed the virus persists for a long time in decaying carcasses of wild boars that succumb to the disease and may facilitate virus persistence for months within a region, significantly influencing the course of an epidemic. Even if the probability of infection for each contact is low, the long-lasting persistence will allow maintenance of virus circulation, Depner said.

Control program

Brook offered a checklist of what is needed to make progress on wild pig control.

One is leadership.

“There’s a real vacuum here and no one is saying, ‘Let’s go kill these pigs,’” he said. “It’s a big deal and nobody is getting on board.”

More research and monitoring is needed as well as disease testing.

He urged producers to be on the lookout for wild pigs on their land.

“Do some test cameras as a cheap and easy way to get started,” he said.

And if wild pigs are found, producers should not allow sport hunting as this will only scatter members of a sounder and exacerbate the problem. Instead, whole sounders need to be captured with all but one killed — that animal should have a tracking collar put on it and then be released so it can lead trackers to other sounders.

“It’s very effective,” said Brook, adding a comprehensive multi-pronged strategy is needed for effective control.

When asked what such a program would cost, he said it would be “bloody expensive.”

“Hundreds of thousands, maybe millions of dollars,” he said. “One thing is sure. Every year you wait it gets more expensive.”

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