Influenza is a respiratory disease. Except when it’s not. Highly pathogenic avian influenza (HPAI) has reminded us once again that viruses find a way to adapt, and influenza is a master at adapting. I can accept that an influenza virus occasionally finds its way from the respiratory tract of a migratory bird into a chicken, or even pig. But a bovine mammary gland?? Come on. Really.
As everyone knows, the influenza virus made exactly that leap earlier this year. At the time of this writing, the virus continues to circulate at will, putting much of the US dairy herd at risk. Fortunately, it is not killing cows, but infection does result in significant, hopefully temporary, illness and losses in milk production. Continued virus circulation, however, poses an increased risk for infection in poultry flocks where exposure results in high rates of mortality and depopulation of entire flocks. To date, we have been fortunate to have avoided swine infections – as far as we know.
Researchers are beginning to explore what the implications might be for an H5N1 infection in swine. We need to understand what clinical signs to expect, how the disease might manifest in swine, how it might be transmitted, any risks to exposure in meat, etc. There are early indications that it might be a relatively mild clinical disease in swine but with possible central nervous system signs raising concerns that the disease might go undiagnosed (or misdiagnosed) for a time.
This is why continued surveillance and sample submissions are critically important. The US Department of Agriculture Swine Influenza Surveillance Program is still accepting submissions from the veterinary diagnostic laboratories and conducting next-generation sequencing to monitor for the emergence of new strains or potential recombination. We have heard, however, that sample submissions are declining due to reluctance to have samples tested because of limited detail regarding the regulatory response.
In response to these concerns, the National Pork Producers Council is leading an effort involving AASV, National Pork Board, Swine Health Information Center, and others to develop an H5N1-specific response plan that can then be shared with state and federal animal health officials. The goal of this effort is to have an agreed-upon response plan ahead of an H5N1 outbreak in swine so everyone understands what will happen when the first, and subsequent, positive herds are detected.
Our only hope of detecting this influenza variant early in an outbreak will likely rely on robust surveillance. The earlier we can detect it, the more options we have of addressing it, controlling it, monitoring it, and ultimately eliminating it. Please encourage your producers to continue to submit suspect samples to the diagnostic laboratory and be vigilant for any production abnormalities. In addition, encourage farm employees to get vaccinated for seasonal flu and avoid contact with pigs if they are not feeling well. While it may not prevent an H5N1 introduction, it will help decrease the number of strains to which pigs are exposed.
Harry Snelson, DVM
Executive Director
AASV resources on Influenza A can be found here.