Post-weaning diarrhea (PWD) caused by E. coli infection is not pretty for pigs or their owners. Finding ways to combat this illness could save producers a bundle in treatment costs and lost production, while improving the well-being of animals and strengthening food safety. Led by Dr. Vahab Farzan, Research Scientist with the Ontario Veterinary College at the University of Guelph, scientists sought a probiotic solution to PWD.

E. coli bacteria that reside in the intestines of humans and some animals are usually harmless, and support a healthy digestive tract. Some strains, however, can produce toxins that cause a number of symptoms such as vomiting, diarrhea and damage to the lining of the intestine. Additionally, infection in post weaning pigs often leads to mortality, making E. coli a major focus of research for the pork sector. Not only does it severely impact the industry in Canada to the tune of $100 – 150 million per year, but it is of great concern around the globe.

Given that it causes dehydration, diarrhea and often death, E. coli is an animal welfare problem as well. Even pigs that recover from the infection may fail to keep pace with others in terms of development, remaining stuck at a lower performance level during the growing stage.

Going all in to keep it out

In light of E. coli’s impact, producers try a range of approaches to keep it at bay. Prevention starts with thorough cleaning and disinfection of all pens from one batch of pigs to another; however, infection sometimes sneaks through in spite of a farm’s best efforts.

Another strategy for guarding against E. coli is the inclusion of antimicrobials in the nursery diet. A popular choice is zinc oxide, which is usually administered in high doses of 2500 – 3000 ppm (parts per million). Because this substance is a heavy metal, too much of it can be toxic for pigs. To guard against this, the animal’s physiology ensures that excessive zinc intake is excreted. That can be a problem, as it means that zinc accumulates in manure and winds up contaminating soil and groundwater.

Keeping Resistance in Check

There is also evidence from previous studies that the gene in bacteria responsible for resistance to zinc oxide is carried on a “mobile genetic element”. This element is a type of genetic material that can move around within the genome of the bacterial population of a pig. The genome is akin to a recipe book for the animal, containing all the instructions for making and maintaining it.

While “mobile genetic element” may sound harmless, it cannot be taken lightly, since it also carries the genes for resistance to other antimicrobials. Left unchecked, it will lead to more resistant bacteria in the pig’s gut, which could eventually inhibit the treatment of future infections in the herd.

Taking your best shot

A critical tool for preventing infection is vaccines. Though they are often effective, they can be of limited value to piglets, whose immune systems are still immature and unable to reap the benefits of vaccination. This led researchers to explore the most promising option, probiotics, which are live bacteria (the good kind) and yeasts that promote gut health and guard against disease.

Pondering Probiotics

Before a control measure such as probiotics can be used at the farm level, researchers need to evaluate the product’s effectiveness thoroughly through experimental challenge trials. This required that they develop an infection model to determine at what age, and with how much bacteria, pigs should be infected by E. coli to show the clinical signs of post-weaning diarrhea. For the benefit of other scientists, the model can now be used as part of future projects.

Additionally, in order for E. coli to infect a pig, the animal must possess a special receptor in the gut where the bacteria can attach and begin to wreak havoc. Absent that receptor, the pig possesses a natural resistance to E. coli, as harmful bacteria are unable to “land” and release their toxins.

Discovery of the receptor’s role in resistance, and refinement of the disease models, are key outcomes which unlock new avenues for future studies. This foundational knowledge should go a long way to protecting pigs from E. coli down the road.

Collaboration Drives Discovery

Science is a team sport, and this project found financial backing from Swine Innovation Porc (SIP), Ontario Pork, and the Ontario Ministry of Food, Agriculture and Rural Affairs (OMAFRA). The project was co-led by Dr. Vahab Farzan from the Ontario Veterinary College at the University of Guelph. Progress was powered by the knowledge of his collaborators, who are also members of the Ontario Veterinary College: Dr. Robert Friendship, professor, and Dr. Brandon Lillie, department chair and associate professor. Dr Joshua Gong, research scientist with Agriculture and Agri-Food Canada (AAFC), also played a large part in the study.

From here, the team will continue running disease challenge trials to evaluate products such as probiotics and vaccines.

In addition to reducing mortality and hindering performance among pig herds, fighting against a devasting enemy like E. coli would address public health concerns around contaminated soil and antimicrobial resistance. Though it can be hard to find a win-win these days, anything that promises healthier pigs and happier consumers is a good start.