In the world of swine health, rule-out testing emerges as the surefire way to determine the cause of blisters in pigs.
Dr. Jette Christensen, the Canada West Swine Health Intelligence Network (CWSHIN) manager, underscores the importance of this approach, emphasizing that it provides the certainty needed to safeguard against Foot and Mouth Disease (FMD) and Seneca Valley virus.
CWSHIN’s recently released swine health surveillance report for the second quarter sheds light on two incidents in Manitoba and Saskatchewan. In both cases, sows displayed troubling signs of blisters, prompting the initiation of FMD and Seneca Valley virus rule testing. The results, however, were negative for both diseases.
Dr. Christensen highlighted the significance of rule-out testing, saying, “It’s a complex investigation because first CFIA needs to rule out Foot and Mouth Disease and Seneca Valley Virus or other viruses that can cause blisters, and then the herd practitioners will come in to figure out, if it’s not Foot and Mouth Disease, it’s not Seneca Valley virus, what is it?”

In one of the cases, laboratory histopathology suggested a potential link to burns. Dr. Christensen explained that “burns” encompasses various causes, including frostbite, sunburns, and chemical burns. However, despite a thorough investigation, the veterinarian couldn’t pinpoint any specific causes of burns within the barn.
“So, we know for that specific herd that it wasn’t Foot and Mouth, it wasn’t Seneca Valley, but we’re not sure what it was,” Dr. Christensen admits.
The story repeats itself on the other farm. Extensive testing ruled out Seneca Valley Virus, Foot and Mouth Disease, and other viruses that could cause blisters. While the vets identified some chemicals as potential causes of burns, definitive laboratory confirmation remained elusive.
Dr. Christensen sums it up concisely: “The bottom line for both of these cases was we know what it was not, but we are not certain what it was.”
The key takeaway from these incidents, Dr. Christensen asserts, is that not all blisters in swine result from bacterial or viral causes. This underscores the critical need for robust surveillance, particularly in Foot and Mouth
Disease cases and the Seneca Valley virus.
She emphasizes, “There are blisters out there, but not all caused by bacteria or viruses. Therefore, our Foot and Mouth Disease and Seneca Valley virus surveillance must investigate every case of blisters thoroughly.”
In the ever-evolving landscape of swine health, rule-out testing is the linchpin to ensuring the well-being of our swine populations. As Dr. Christensen aptly demonstrates, ruling out potential diseases is an essential part of the puzzle, allowing them to eliminate threats and focus on safeguarding the health and vitality of our swine herds.
“With each case of blisters meticulously examined, we strengthen our defences and enhance our ability to protect against the most significant challenges facing the swine industry.”
Dr. Christensen said there are blisters out there but not all are caused by bacteria or viruses. Hence, it’s critical for the Foot and Mouth Disease and Seneca Valley virus surveillance for every case of blisters to be investigated. •
— By Harry Siemens