Pharmagap Inc., an Ottawa-based biotechnology firm, in conjunction with PEI Pork and the Canadian Centre for Swine Improvement (CCSI), have devised a Swine Disease Resistance (SDR) blood test that measures an animal's immune response to both bacterial and viral infections.
The simple laboratory test will potentially allow seedstock suppliers to develop breeding lines with dramatically improved disease resistance and, that hopefully, will ultimately reduce producers' dependency on antibiotics.
“This test will hopefully let us separate the animals with a stronger immune system from the ones with a weaker (immune) system so we can breed and select for the stronger ones,” says Daniel Hurnik, Industry Chair for Swine Research at the University of Prince Edward Island in Charlottetown, Canada.
All that is required is a blood sample that is analyzed in the laboratory for immune response.
“In the SDR test, we chemically stimulate the white blood cells, the immune system's soldiers,” says Robert Letellier, President of Pharmagap. “This causes them to start working and multiplying as if they have encountered an infection. Afterwards we count the number present after the exposure. The larger the number of white blood cells that we find, the stronger the animal's immune response will be. The test works very well.”
“It is really simple and practical,” adds Hurnik. “We have finished the proof-of-concept stage of testing of the technology.” Research on heritability will soon follow.
Implications for Antibiotic Use
Reduced antibiotic usage is becoming more important to livestock producers all the time. Hardly a month goes by without a story on how yet another type of bacteria has developed antibiotic resistance. Rightly or wrongly, antibiotic use in livestock production is often blamed for the problem. Consumer pressures are forcing livestock producers to reduce antibiotic use whenever possible. Cost, too, is an issue for producers. The North American swine industry annually spends about $1.5 billion ($US) in health care.
“Antibiotics are used to control disease in swine production. If we can't use antibiotics, how do we control disease?” Hurnik asks. “What alternatives are there?
“Can we make animals more resistant to disease? The answer to that is yes. Nature does this all the time. Tropical cattle, for example, are resistant to certain diseases. If you take cattle from here to Africa, they die. We know that hardiness is an inheritable trait. A number of geneticists and immunologists around the world have been looking at this issue, but the bottom line is, how do we select for disease resistance?”
Studying the Possibilities
Perhaps the simplest way to test for disease resistance is to expose an animal to a disease and then mate the ones that survive. The problem is that unless you are dealing with a really virulent, deadly disease, you just wind up with a lot of sick animals, Hurnik explains. In practice, this raises all kinds of issues. How do you have healthy, disease-free breeding stock if you are constantly exposing them to disease? Nobody wants to deliberately make pigs sick.
At present, Pharmagap is working with PEI pork and CCSI to test a sample large enough to be able to categorize individual animals as having either a strong or weak immune response level.