Some spectres come back to haunt us

Are you afraid of ghosts and goblins and other shades of the night?

At this Hallowe’eny time of year, it’s easy to get morose about the ghosts of grey and cold and drear dark that begin to invade our minds in the days before the white of winter lifts our spirits.

But farmers don’t need to feel the vague fears of abstract ghostly haunting. They are living with the reality of two ghosts that are haunting prairies again, after having faded to near-ecotplasm status in recent years.

This was the year when  blackleg came back to spook canola growers. The disease has never gone away, but in recent years did much less damage than farmers had suffered from it in the 1990s and early 2000s. Some producers could be forgiven for assuming that our doughty scientists and crop variety developers had managed to evolve canola away from being vulnerable to blackleg, and that it had become just a ghost haunting our memory. With the right conditions – humid early, hot and dry later – blackleg arose once more from that dark corner over there and began rattling its chains. Rather than fading, it had simply slunk away for a while, to evolve new races that are now back out there in the field. Blackleg is again something we have to fear.

So too do we have to once more fear the spectre of swine dysentery.

For decades prairie farmers and veterinarians thought swine dysentery – one of the products of the brachyspira family of diseases – had gone away for good. It just didn’t happen any longer in North American hog barns. It faded to a memory among older farmers and vets, and wasn’t even known to young producers and vets. It was just another ghost from the past, haunting memory but not reality.

That was true until a few years ago, when it began appearing again, frightening farmers and vets who had never seen it before. “Atypical diarrhea” began showing up in the labs, and sure enough – swine dysentery was back amongst us.

Where do these dread fears go when they retreat from our world? In what corner was brachyspira skulking, collecting its haunting powers? Did it have a few reservoirs somewhere that let it linger? It’s a disease that can live amongst the rodents and waterfowl without making any signs, so likely it hid there until recently.

Blackleg never went away, but its damage did for most producers. The sometimes-devastating outbreaks of blackleg – the kind of outbreaks the Chinese say they fear when they ban our canola from entering many Chinese ports – stopped happening to most farmers as new canola varieties got tougher and more resistant to the fungal phantom. But it was out there everywhere, and evolving. Canola experts have been warning farmers that new types of blackleg are out there, and this year their warnings were followed by many farmers having problems. The right combination of weather occurred, and blackleg was back amongst us as a major worry.

Will these two diseases continue to haunt us? Swine dysentery looks like its going to stick around, although good management can make it not much more than an occasional, treatable problem. Same with blackleg. It isn’t going away, but good rotation and treatment can make it flee like a ghost faced with the dawn.

But gone are the days when we could assume either disease was just a phantasm from past memory and not something we needed to worry about today. Ghosts have a way of retreating during the daylight, but being there to haunt us the next long, dark night.

(All images from wikimedia commons.)



Stories from our other publications