IAV-S — An ongoing threat to productivity
Influenza A virus in swine (IAV-S) is an economically damaging respiratory disease in pigs, endemic in most herds, and responsible for widespread losses in productivity.1,2 Managing the threat of IAV-S requires a comprehensive approach to herd management and disease control.3,4 In this section you will find helpful information about IAV-S, its cause, and its impact on productivity and health.
Introduction to IAV-S
Prevalence and endemicity
IAV-S is a prevalent pathogen affecting all phases of an operation.
Significant morbidity and mortality7,8
For the swine industry, the economic impact of viral infections can be severe. One of the most common viral diseases in pigs is influenza.8 It causes clinical signs that affect mortality and reduce weight gain and feed efficiency.8
IAV-S–infected pigs are susceptible to co-infection with other bacterial respiratory agents (Streptococcus suis, Haemophilus parasuis, Actinobacillus suis, etc.). Concurrent Mycoplasma hyopneumoniae (Mhp), porcine circovirus 2 (PCV2), and porcine reproductive and respiratory syndrome virus (PRRSV) infections are a significant contributor to poor performance.9
The Infection Chain™ provides a visual tool to promote discussion of controlling infection through an understanding of how, through each phase of production, it is most likely to spread.
Widespread impact on performance
As a component of the porcine respiratory disease complex (PRDC), IAV-S infection can have a detrimental impact on the performance in the grow/finish stages of production. Although the economic ramifications of IAV-S infection alone may be difficult to measure in the field setting, pigs affected by PRDC are known to have poor performance as they are infected with multiple primary respiratory pathogens.
IAV-S can spread across all production phases. Therefore, it can be endemic in large populations, even in all-in, all-out operations.10
IAV-S survives in a pig population because of the presence of non-immune animals. Thus, sow farms, in particular, can become endemic because of the routine entry of replacement animals and the birth of naive pigs.2
The disease reduces weight gain. Non-immune young may have variable amounts of maternal antibody to IAV-S, which allows the disease to have a prolonged impact in nursery populations and makes the pigs susceptible to secondary infections. Growing pigs can be hit hard with acute IAV-S, which can also significantly reduce feed consumption and increase mortality. 11
In one study, linking historical diagnostic reports with closeout information to determine the production and economic impact of swine influenza virus, the theoretical additive cost of separate Mycoplasma hyopneumoniae (Mhp) and IAV-S infections was $3.86, but the actual cost for these pathogens when occurring concurrently was more than double that figure. Similarly, the economic losses associated with concurrent porcine reproductive and respiratory syndrome (PRRS) and IAV-S costs were significantly greater than the additive costs of PRRS and IAV-S alone.1
IAV-S and the impact on growing pigs
Historically, phase-specific respiratory pathogen burden, from the time of weaning to marketing, has not been well characterized. This poses a considerable challenge to producers to effectively evaluate the association between the timing, duration, and concurrent infection of key respiratory disease agents and performance outcomes.
A recent study reported by Iowa State University analyzed the burden of respiratory disease during the growing period as it relates to multiple pathogens, including IAV-S and PRRSV.12
Studying pathogen burdens through production
The study described by Iowa State University measured pathogen burden from oral fluid sampling. Forty-five flows (independent groups of pigs) were sampled every 2 weeks from nursery placement through closeout. The results of these diagnostics determined 3 main “patterns” of burden for each pathogen. The study then coupled the diagnostic data with the total mortality data reported from each enrolled group.
Flows that were seen to have growing nursery pathogen burdens (moving from low to moderate-high pathogen burden in the nursery) had the highest average mortality rates; over 40% greater than any other pattern for IAV-S, and 80% greater than any other pattern for PRRSV. Based on these mortality rates, average daily gain (ADG) for the affected flows would be negatively impacted as well.
In flows where IAV-S and PRRSV move from low to highest burden in the nursery, this compounded late nursery pathogen burden affected overall mortality rates even more, climbing from 10.4% and 10.1%, respectively, for the individual pathogens to a combined 13.7%.
Controlling IAV-S leads to better health outcomes1
The presence of an increased burden of respiratory pathogens inevitably leads to increased numbers of diseased pigs. When pigs are affected by respiratory disease, lost productivity has been shown to impact the ability of pigs to reach their full potential.1