With humans, illness may just keep us home from work for a day or two (or three if we still have sick time to use). For pigs on the other hand, disease is often debilitating or fatal, and too much disease can affect the producer’s bottom line. That reality is at the heart of a new Genome Alberta-led research project aimed at boosting disease resilience in pigs through the cutting edge use of genomics.
There are actually four separate activities within the project. One of them, entitled “Activity 2.1 - Developing Ex Vivo Models to Evaluate Resilience”, is focused on resilience to enteric diseases, which are those that cause diarrhea in pigs.
“Assessing resilience to enteric diseases in livestock populations is complex because there are no simple laboratory tests to quantify genetic or phenotypic resilience,” said Project Lead Dr. John Harding from the University of Saskatchewan. “Furthermore, animal challenge studies are generally small and use a single challenge organism and dose.”
As Dr. Harding pointed out, experiments involving animals are generally quite costly; thus the need for alternative research methods.
Is bioassay the way?
One approach that shows great promise involves bioassays, which use live animal tissue to determine the biological activity of a substance.
“We’re trying to develop a screening method that can measure resistance to enteric infections,” said Harding.
He explained that regardless of what disease you deal with, some animals get sick and some don’t. Researchers often don’t know why, but that may soon change.
“There are underlying genetic predispositions for some animals to develop more severe diarrhea than others,” said Harding. “By using this bioassay screening method in the lab, we can collect intestines from donor pigs, grow intestinal cells in the lab and test them for a new disease; so instead of using an individual animal once we can use it several times.”
Picking the pathogens
In Activity 2.1 of this project, the focus is to use those intestinal cell lines and expose them to different pathogens, starting with the Porcine Epidemic Diarrhea (PED) virus. The researchers will then use the colonic cells from the large intestine and expose them to Brachyspira hyodysenteriae, a bacterium causing swine dysentery.
“Starting with these two key diseases, we will screen 100 pigs supplied by PigGen Canada so we have a diverse set of breeding lines to work with,” said Harding.
By measuring the pigs’ response to PED and Brachyspira bacteria, they can determine which animals are resistant and which are susceptible to the diseases. From there, they use a transcriptome approach (measuring which genes are actually turned on and working) to determine the difference between the resistant and susceptible pigs; why they are the way they are.
Brave new (diarrhea-less) world?
Of course, being on the forefront of research is both exciting and frustrating.
“This is really novel from a technique point of view, getting intestinal cells to grown in petri dishes. At the same time, it’s a challenge, especially with the small intestine cells. We’ve had some success but we’re still working on the methodology to get more consistency.”
Harding is confident that once they get that consistency, the infection process will be easy.
By the way, if you ever think researchers have it easy, try spending your day immersed in pig diarrhea research; you may think twice.
A gram of prevention…
In spite of the challenges, Harding is excited by the prospects of this project.
“Veterinarians always wonder why ‘pig A’ got sick while ‘pig B’ is healthy. If, instead of wondering, we can screen for an underlying genetic predisposition and do something about it, we can really focus on prevention instead of just treatment, and that’s powerful.”
And as is the case with much genomic research, the possibilities are endless.
“Once we get our tests up and running, we will be sampling exotic breeds as well to see if they have higher or lower levels of disease resistance.”
From there, who knows? Maybe we’ll target those human illnesses that keep us home sick, and we’ll never have to miss work again. On second thought, we might want to hold off on that one.
Protecting Pigs and Profits with Genomics Technology