Dr. Matt Loewen, an Associate Professor in Veterinary Medical Biosciences with the University of Saskatchewan’s Western College of Veterinary Medicine is confident they can apply to other pathogens a new approach to dealing with bacterial diarrhea in pigs.
To assist in vaccine development, researchers with the Western College of Veterinary Medicine have isolated two specific Brachyspira hyodysenteriae proteins that appear to be responsible for diarrhea in pigs.
The University of Saskatchewan is researching the mechanisms of diarrhea aimed at developing strategies to prevent diarrhea in pigs.
“There are two classes of pathogens that would cause diarrhea, one being viral and the second one being bacterial,” said Dr. Loewen. “Right now, we’ve focused on both because they’re both economically important. Both types of diarrhea caused by both pathogens are important for Western Canada. The viral one is the big one out there for the last couple of years, porcine epidemic diarrhea virus, and several other viruses will cause diarrhea, too.”
Dr. Loewen said scientists returned to first principles and looked pointedly at what the bacteria produce and how the pig reacts to it to cause diarrhea.
“If they are strongly immunogenic and a good antigen, that the pig can take those antigens and produce a response to them that prevents the bacteria from functioning,” he said. “This concept of going back to first principles of what’s happening in the pig, in the bacteria, and knowing the particular proteins and processes involved. Then targeting particular things in the bacteria to produce an immune response successful in other diseases, in particular for cholera in human vaccines.”
He thinks if this process works, they could apply it to other pathogens that are problematic to pigs such as other E. coli diarrheas and Salmonella and even some of the viral diarrheas.
“If it works, then we can probably move this to another pathogen,” said the researcher. “That said, the time frames to do this type of work are huge. You’re taking a decade or more to go back to very first principles, figure out what’s happening and find the specific proteins that you’re after.”
Dr. Loewen acknowledges, because of the timelines involved, this process is unlikely to replace the commonly used methods of vaccine development completely.
He said the problem with brachyspira hyodysenteriae for the longest time the industry could control it with biosecurity and antibiotics. The amount of antibiotic use is limited, and biosecurity works only to a certain degree.
“What we would like is a vaccine for it, and that has eluded us for years. Because the industry needs a vaccine for brachyspira right now, we focused in on this pathogen in hopes of producing one and coming at it from a different perspective,” said Dr. Loewen.
Instead of grinding the isolated bacteria from a farm, then trying to make a vaccine, or taking the proteins from a bacteria and looking at the immunogenicity of it, they went back to the pig.
“What is the bug producing to cause diarrhea; what’s coming out of the bacteria and causing diarrhea,” said Dr. Loewen. “We were then able to identify two proteins that were very central to causing those changes in the pathophysiology.”
The researchers found these two proteins seem to recapitulate a lot of what the bacteria can do without the bacteria being there.
“But if the pig produces a specific immune response against these very central proteins to the bacteria and its ability to cause disease, then you will hopefully prevent the disease. It’s a very long process in comparison to what has been done previously to try and create a vaccine for brachyspira,” Dr. Loewen said. •
— By Harry Siemens
