Diagnostic laboratories consistently rank influenza among the most frequently tested pathogens, and industry data repeatedly place it among the top causes of respiratory disease. If everyone can agree the swine industry has a flu problem, why has the industry largely decided to live with it?
“The ship has sailed on prevention at this point,” says Andrew Bowman, DVM, PhD of The Ohio State University’s College of Veterinary Medicine, at the American Association of Swine Veterinarians (AASV) meeting in Las Vegas. “We are somewhere in control or elimination. And if we want to move the needle, we’ve got to start drifting toward elimination.”
Influenza A virus (IAV) in swine is typically not an isolated event, but rather a key contributor to the porcine respiratory disease complex (PRDC), which inflicts significant economic losses through reduced weight gain, increased days to market, and reproductive inefficiency, Bowman says. However, IAV in swine has broader implications beyond the barn door.
“Swine are well-established as ‘mixing vessels’ for human, avian and swine influenza viruses, facilitating genetic reassortment that can generate novel viruses with zoonotic and pandemic potential,” he says. “Our commitment to controlling IAV in swine herds is, therefore, a frontline defense for both the pork industry and public health.”
Management Versus Elimination
Bowman believes the bigger issue is not lack of information, but the goal the industry has set for itself. Many production systems focus on managing influenza rather than eliminating it.
“The most pervasive obstacle we face is not the virus itself, but a sense of futility summarized by the statement, ‘Why bother? We are just going to get it again.’ This perspective fundamentally misunderstands modern IAV epidemiology,” he says.
This passive acceptance enables IAV to establish the endemic circulation we see in many production systems, Bowman adds.
“The virus’s circulation in other hosts and its ability to evolve rapidly are not justification for inaction,” he says.
Rather, Bowman believes these are the very reasons proactive, persistent control is non-negotiable.
“Allowing uncontrolled circulation effectively gives IAV unlimited opportunities to shift and drift, all but guaranteeing that we will, indeed, ‘get it again’ in a costly and predictable cycle,” he says.
The pork industry should take the lead in driving change by moving away from reactive treatments and accepting an endemic state, actively working to eliminate IAV in herds rather than merely managing it, Bowman says.
“This is not about finding a single ‘silver bullet’ vaccine, but about implementing a concerted, multi-faceted strategy,” he adds. “This will take innovative thinking, challenging dogma and substantial effort.”
Can Influenza Be Eliminated?
Bowman says IAV meets all the typical criteria used to justify elimination programs. IAV directly affects three major areas of concern for the pork industry:
• Animal health
• Economics and production performance
• Zoonotic risk at the animal-human interface
“Influenza hits all three,” Bowman says.
The tools needed to reduce IAV circulation are not new or complicated, he points out. Across numerous research studies and field experiences, the same core strategies repeatedly appear in successful elimination efforts:
• Isolation or segregation of pig populations
• Strong biosecurity protocols
• Strategic vaccination programs
“It’s not rocket science,” he says. “Those three things — isolation, biosecurity and vaccination — are the tools we have, and they work. They are the same issues being discussed for porcine reproductive and respiratory syndrome virus (PRRSv) elimination, so it would be quite easy to shift from PRRSv elimination to also include IAV elimination in swine.”
Influenza diversity in swine has increased over time, making vaccine strategies more complex. But Bowman notes that diversity does not eliminate the effectiveness of biosecurity or pig flow management. Instead, he frames the challenge as one of industry mindset.
“While we may not always be able to prevent IAV infections, we can reduce clinical disease, decrease viral shedding and critically limit the probability of reassortment events within swine herds,” he says.
