Swine dysentery is a disease that causes bloody and mucoid diarrhea in pigs. Several species of bacteria called Brachyspira cause this disease in grower-finisher pigs (young pigs over two months of age being fed to reach market weight).
Although swine dysentery doesn't usually kill pigs, it does stunt their growth for one to two weeks. It also decreases feed efficiency and increases medication usage. And in an industry where every dollar counts to keep a farm in operation, lost production time is a major concern.
Historically, bloody diarrhea was caused by a bacteria species called Brachyspira hyodysenteriae. But in 2009, WCVM researchers discovered a "new" Brachyspira species, now called "Brachyspira hampsonii," in pigs from two Saskatchewan pork farms.
B. hampsonii has since been found across Western Canada and causes disease that is indistinguishable from B. hyodysenteriae. So far, laboratory testing is the only way to make an accurate diagnosis.
Drs. John Harding and Janet Hill, who are professors and researchers at the WCVM, have been involved with this issue ever since two Saskatchewan veterinarians presented the first cases of B. hampsonii-related bloody diarrhea to them in 2009.
"It [B. hampsonii] is indistinguishable from swine dysentery. We can't tell it apart and there are no commercial vaccines on the market," says Harding, who hopes their research will lead to the development of a vaccine against this new bacteria species.
Hill, a veterinary microbiologist, has developed a technique to identify B. hampsonii in tissue and manure samples from infected farms. Using a test called polymerase chain reaction (PCR), the samples can be tested to determine whether or not bacterial DNA is present. This PCR was adapted for use on paraffin-embedded tissues.
My project uses these new techniques to test "cold cases" and determine if B. hampsonii actually existed before its discovery in 2009. I'm looking at old cases of diarrhea in pigs, especially those cases where a cause for the disease was not found.
And where would a good detective be without her team? In addition to my supervisor, Dr. Susan Detmer, I rely on Harding, Hill and WCVM veterinary pathologist Dr. Bruce Wobeser as well as research technicians Betty Chow-Lockerbie and Champika Fernando.
The first step is to track down these cases. Using a computer database, I comb through hundreds of archived cases of pig illnesses to find ones matching the description of swine dysentery. After weeks of sleuthing, I manage to find over 100 suspect cases dating from 1984 to 2009.
Once the computer work is done, I grab my stepladder and head to "evidence storage" – also known as the veterinary college's basement. Thousands of tissue samples have been saved during the past 40 years and stored in boxes. My task is to search by case number to find the cases I want to test.
I brush cobwebs out of my hair and with tissue samples in hand, I am off to the lab where I cut and extract DNA from these samples. After my DNA samples are ready, I head down the hallway to the college's molecular microbiology lab and perform the PCR tests to find out if my suspect has left its fingerprints on these cases.
So far, we have exciting preliminary results indicating that B. hampsonii did exist before 2009. We have more work to do to confirm these results, but I look forward to presenting our findings at the student research competition of the American Association of Swine Veterinarians' conference in March 2015.
This research will provide important clues for the research team: by learning more about when this pathogen developed and where it came from, we can figure out how to stop it from getting into swine barns.
And that knowledge will allow the industry to develop more successful biosecurity and control programs in the future.
Stephanie Derbawka of Borden, Sask., is a fourth-year veterinary student who was part of the WCVM's Undergraduate Summer Research and Leadership program in 2014. Stephanie's story is part of a series of articles written by WCVM summer research students.