Influenza: A Growing Threat to Your Herd's Potential

October 30, 2017 10:33 AM

Production losses from influenza can total more than $3 per head


Influenza-A virus (IAV-S) has been present in U.S. swine herds for nearly 100 years,1 and until recently, was less complicated for producers and veterinarians to manage. Today, however, due to its endemic presence in swine populations in North and South America, Asia and Europe,1 as well as the emergence of new virus strains that are more difficult to predict and control, IAV-S has emerged as a major threat to the industry overall.


Nowhere is that threat more easily recognizable than in production losses associated with IAV-S. A 2012 study that looked at losses associated with average daily gain, culls and mortality rates among hogs with IAV-S estimated that the virus, when present alone, costs producers $3.23 per head.2

In addition, one of the effects of IAV-S is that it attacks the cells that line the respiratory tract of pigs, weakening their first line of defense against subsequent respiratory infections. The same study found that when IAV-S is present with porcine reproductive and respiratory syndrome (PRRS), it led to even greater production losses that totaled $10.41 per head.2 And when present with Mycoplasma hyopneumoniae, it costs producers $10.12 per head.2 Unfortunately for producers, these concurrent infections are all too common.

“Rarely do you find IAV-S by itself in swine,” says Christa Goodell, DVM, MS, Ph.D., DACVPM, technical manager at Boehringer Ingelheim. “More often, it’s going to be present with other diseases in the porcine respiratory disease complex. So, you have multiple respiratory pathogens affecting the pig at the same time, which can make diagnosing and treating them extremely difficult.”

IAV-S Transmission

Recognizing IAV-S in a herd is the first step to addressing it. An uncomplicated infection has an approximately 10–14-day timeline, with clinical signs including fever, coughing or sneezing, runny nose, difficulty breathing, going off feed, and lethargy appearing early in the infection.

The peak time for transmission occurs within the first 48 hours. IAV-S spreads most often through direct, nose-to-nose contact between pigs, through the air and via contaminated objects like sort boards, processing carts and equipment. The virus commonly infects pigs in the later stages of the nursery phase, between 8 and 10 weeks of age, and early in the grow/finish phase; however, pigs of any age are susceptible, according to Phil Gauger, DVM, MS, Ph.D., associate professor at Iowa State University College of Veterinary Medicine. And because IAV-S infections can often be subclinical, they can go undetected until it’s too late and entire herds have been exposed. (IAV-S is not a disease that gets in the blood, and therefore is not passed on to pigs in utero or through milk.)

Not only can the virus spread quickly, it has the ability to mutate and form new strains. In the last decade, multiple new strains have emerged, which has caused IAV-S to become increasingly difficult to manage.1 Existing vaccines do not have the cross-protection needed to effectively defend against such a dynamic threat.

“Right now, it seems as though many of our control methods through vaccination and biosecurity just haven’t been enough, in spite of our best efforts to control IAV-S,” says Dr. Gauger. “The frustration is high. People are ready to toss their hands in the air and say ‘We don't know what to do anymore.’ So, it’s become a problem of just trying to manage it as best we can, even though preventing IAV-S entirely has become extremely difficult.”

Goodell recommends talking with your veterinarian about Influenza-A virus to learn more.

1 USDA. Swine disease information. Available at:​sease-information. Accessed August 17, 2017.
2 Dykhuis Haden C. Assessing production parameters and economic impact of swine in influenza, PRRS and Mycoplasma hyopneumoniae on finishing pigs in a large production system, in Proceedings. 43rd American Association of Swine Veterinarians Annual Meeting 2012;75–76.
©2017 Boehringer Ingelheim Vetmedica, Inc.
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