Farmscape Article 2230  August 26, 2006

Despite the deaths of three pigs in Saskatchewan from anthrax, the risk of swine becoming infected by this particular disease, especially those housed in modern confinement facilities, remains extremely low.

Figures released August 25^th by the Canadian Food Inspection Agency (CFIA) show 693 animals on 147 Saskatchewan farms have died from anthrax during the worst year on record for the disease in the province. Included in that number are three pigs which were housed on one small outdoor swine operation in the Prince Albert-Kinistino area.

In Manitoba 137 animals have died on 21 premises, none of them hogs. In both provinces cattle have accounted for the vast majority of infections.

Anthrax Considered a Product of Environmental Conditions

“Anthrax is considered to be an environmental disease,” explains CFIA disease control specialist Dr. Sandra Stephens. “[Bacterial] spores that are the causative agent for anthrax are potentially buried and located in any number of places across western Canada. It’s not an infectious disease in the typical sense that it doesn’t spread from animal to animal. It’s something animals acquire from the soil.”

She explains, “We do tend to see a couple of environmental conditions that tend to result in exposing spores to grazing animals. The one would be similar to what we’ve seen in northeast Saskatchewan where we’ve had an extensive amount of rainfall, snow cover followed by more rainfall so there’s soil saturation, flooding. As those flood waters and the water starts to dry up from those saturated soils, the spores which are buoyant and have floated to the surface tend to get left behind on the soil.”

She adds, “The other would be prolonged periods of dryness or drought. In those situations we start to see pasture starting to get eaten back and growth of grass isn’t good so animals are grazing closer to the ground picking up more dirt which potentially could contain spores.”

Ruminant Mammals Face Greatest Risk

Dr. Stephens notes, “All mammals are considered to be susceptible but certainly within that there’s kind of a gradation of which ones are the most susceptible down to which ones are the least susceptible. Certainly at the top of the list we would have our herbivores which would be cattle, sheep, goats, elk, bison, and white tail deer. Those types of animals would appear to be the most susceptible. Then we would go to horses after that and move down into swine, people and then carnivores. Carnivores seem to be the least susceptible.”

Regina based CFIA veterinarian Dr. Greg Douglas adds the one Saskatchewan swine operation affected by anthrax is characterized as, “a backyard operation.”

He says, “It is an operation that keeps the animals outdoors on the land and they graze very similar to an outdoor ruminant operation. Though swine are more resistant to the disease, if the infection pressure is high enough [as it] obviously [is] in this particular case, they can get enough spores where they will get an infection.”

Biosecurity Virtually Eliminates Anthrax Risk in Swine

Dr. John Harding, an associate professor at the Western College of Veterinary Medicine agrees, “We normally think of anthrax affecting ruminants more than swine but it is reported in swine, although very rare.”

He suggests, “The only swine in Saskatchewan or the prairies that are likely to be contaminated would be those that are either feral swine, living outdoors all the time, or would be domestic swine that are outside on pasture.”

He notes, “Our modern systems where pigs are housed indoors, there’s good shower in and people biosecurity, and absence of contamination by soil, I think make anthrax really rare.”

Confinement Production Allows Biosecurity to Work

Dr. Shawn Davidson of Davidson Swine Health Services in Aneroid, Saskatchewan recalls, “Biosecurity came about when we started moving to confinement systems many years ago because confinement systems allowed us to have proper biosecurity. Obviously when pigs are housed outdoors, it’s very difficult to control their exposure to soil and thus, to parasites or any other soil borne organisms but, once we moved them into confinement barns, which started to happen 30 or 40 years ago, it’s allowed the industry to be able to secure these facilities from pathogen introduction.”

He explains, “The goal of biosecurity is to keep key production limiting diseases out of swine populations. If you have a clean herd, it’s a lot cheaper and a lot more effective in the long run to keep that herd free of diseases like PRRS and mycoplasma and APP or actinobacillus pleuropneumonia. It’s far more economical to maintain a herd of that health status than it is to deal with one once they break with one of those diseases. The way we do that is to establish a clean population and then with proper biosecurity measures maintain that health status.”

PRRS and TGE Set the Standards

Dr. Davidson suggests PRRS and TGE are the two diseases by which the standards are actually set for biosecurity in western Canada, “They are the ones that move around readily.”

He notes, “Most of our biosecurity programs are set up surrounding the prevention of introduction of PRRS. PRRS is economically an extremely important swine disease and we know that herds that remain PRRS free are in the long run more productive than those which are PRRS positive. So it’s probably the biggest concern from a biosecurity standpoint.”

“The PRRS virus will survive, particularly in a frozen state, for a good number of hours so we know that it can potentially be transmitted in a transport vehicle like a livestock trailer.”

He maintains, “Biosecurity protocols surrounding transportation, washing and disinfecting of trailers, and downtime for those trailers from the time that they’ve been to a slaughter plant until they return to a farm are all very important measures.”

As well, he acknowledges, “People are not known to be vectors of PRRS per se. But since we know that it can survive outside of a pig for some period of time, making sure that people have complete clothing changes and that shoes that may be contaminated with pig manure are never worn from one facility to the next and those types of measures are very important in preventing the introduction of that virus.”

TGE Less Common but Also a Consideration

As for TGE, Dr. Davidson continues, “We haven’t seen TGE or Transmissible Gastro Enteritis in western Canada for a good number of years but we did see some in the past winter.”

“It also is very resistant to the environment and it freezes very well. It’ll survive for long periods of time in a frozen state. It survives for very long periods of time in hog manure. So, if there’s any movement of hog manure from one facility to another, be that in a vehicle like a transport vehicle, be that on a person’s shoes, be that by what ever means manure can potentially move around, you can see some fairly devastating health breaks with that virus that could be prevented with proper biosecurity measures.”

“A lot of the biosecurity protocols that are put in place by veterinarians,” he concludes, “are put in place with the introduction of these viruses in mind.”

Staff Farmscape.Ca