Farms.com Home   Expert Commentary

Influenza: a growing threat to your swine herd’s potential

Nov 17, 2017

Subscribe to our Newsletters

Influenza A virus in swine (IAV-S) has been present in U.S. 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 case 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, cost the producer $3.23 per head.2

The Economics of Concurrent Infections

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 was present with Mycoplasma hyopneumoniae, it led to even greater production losses that totaled $10.12 per head.2 And when present with porcine reproductive and respiratory syndrome (PRRS), it cost the producer $10.41 per head.2 Unfortunately for producers, these concurrent infections are all too common.

“It’s not common to find IAV-S by itself in swine,” says Christa Goodell, DVM, MS, PhD, DACVPM, technical manager at Boehringer Ingelheim. “More often, it’s going to be present with other pathogens 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.”

Clinical Signs of IAV-S

Recognizing IAV-S in a herd is the first step to addressing it. An uncomplicated infection has an approximate 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. IAV-S is not a disease that gets in the blood, and therefore is not passed on to pigs in utero or through milk.

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 all stages of production, but is found particularly in early nursery when pigs are weaned and comingled, late nursery, as maternal antibodies wane,  or in the grow-finish phase in swine dense areas or continuous flow sites; but pigs of any age are susceptible. Additionally, because IAV-S infections can often be subclinical or have co-infections, they can go undetected until entire sites have been exposed

Not only can the virus spread quickly, it has the ability to mutate and form new strains. In the last 20 years, multiple new strains have emerged, which has caused IAV-S to become increasingly difficult to manage,1 and achieving solid cross-protection against such a dynamic threat is difficult.

“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 Phil Gauger, DVM, MS, PhD, associate professor at Iowa State University College of Veterinary Medicine. “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 IAV-S to learn more, or visiting www.aboutswineinfluenza.com.

###

References

1 USDA. Swine disease information. Available at: https://www.aphis.usda.gov/aphis/ourfocus/animalhealth/animal-disease-information/swine-disease-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