Delving deeper into swine dysentery

But behind the scenes, the pork industry has been greatly affected by swine dysentery (SD), a disease that still lacks an effective vaccine. That’s an important concern for producers as they strive to keep their animals healthy while reducing the use of antibiotic drug treatments.

Researchers at the Western College of Veterinary Medicine (WCVM) are optimistic that a vaccine is within their reach as they investigate the disease mechanism of SD by capitalizing on the advancements of DNA sequencing technology.

Led by Dr. Matheus Costa from the WCVM’s Department of Large Animal Clinical Sciences, the team is focused on Brachyspira bacteria, the culprit behind swine dysentery. Brachyspira infects a pig’s large intestine and causes lesions, which results in watery to mucoid diarrhea — often with traces of blood. As the affected pigs get sick, they lose their appetites and become dehydrated and thin.

“If we understand exactly how Brachyspira infection leads to swine dysentery, we’ll have a better chance at making a vaccine that works, and we’ll also get a better chance to develop other tools — non-antibiotic alternatives that will prevent disease,” explains Costa.

One ongoing project for understanding the disease mechanism is investigating the pathway by which Brachyspira affects the response of B cells — the cells responsible for producing antibodies.

Since vaccines are typically aimed at stimulating B cells to produce these antibodies and the scientists have learned that Brachyspira affects B cell activation, they’re looking for a different approach to developing vaccines for SD.

“In the ’70s and ’80s, there were some brilliant experiments using the technology available at the time to investigate the disease,” says Costa. 

“Now, we have much better methods, and we understand the molecular changes that happen in the colon and the pig in general. So, we’re in a better place to develop a vaccine that will be efficient and that will protect pigs, or at least prevent severe disease.”

Until a vaccine has been developed, producers can lower the risk of infection by maintaining standards of biosafety and checking for signs of disease from incoming pigs.

Unfortunately, Brachyspira is oxygen-tolerant and can survive outside the intestine for extended periods of time so that it’s easily transmitted through manure or carriers such as rats. As a result, biosafety measures can only go so far as long as the bacteria’s infection mechanism remains a mystery.

Since the first description of swine dysentery was published a century ago, the disease has severely affected animal welfare and caused global production losses. Aside from animal welfare concerns, producers face significant financial losses as diseased pigs experience slower growth rates, forcing farmers to spend more resources feeding them and adding antibiotic drugs to their feed.   

In addition to the significance of this research for the livestock industry, the development of a vaccine is also critical to public health as a means for maintaining food security and sustainability and for decreasing antibiotic use. 

“It’s the One Health concept that I believe should always interest anyone who is human,” says Costa. “You don’t live in this planet alone; you live here and you interact with billions of organisms every day, from bacteria to trees to the animals or plants that you eat. If you don’t think about them and their health, people are not going to be healthy either.” 

Christine Tien Yang of Langley, B.C., is a fourth-year Integrated Sciences student at the University of British Columbia who worked as a University of Saskatchewan summer research student in 2021. Her story is part of a series of articles written by WCVM summer research students.