The PRRS Calculator is a decision support tool that quantifies the economic impact of PRRS and models the return on mitigation strategies, including air filtration. It builds on the economic impact assessment published by Holtkamp and colleagues in 2013. Its stated practical conclusion is that preventing a single outbreak will typically justify the filtration investment.
That conclusion depends on inputs that vary between sites, which is what makes a calculator the right form for it. Holtkamp and colleagues put the annual economic impact of PRRSV on US pork producers at 664 million dollars in 2011 dollars, a national aggregate that says nothing directly about any individual herd. The financial companion to the Alonso 2013 work reported payback of 2.1 years on a 150 dollar per sow attic filtration investment and 2.8 years on a 200 dollar per sow attic plus sidewall investment, with the authors cautioning that those figures are long term averages not intended to apply to individual herds and not applicable to low PRRS risk herds.
The useful discipline a tool of this kind imposes is that it forces the assumptions into the open. Break frequency, herd size, the value assigned to a negative weaned pig and the replacement schedule for filters and prefilters all enter the calculation, and each of them is a site specific number rather than an industry constant. A payback figure produced without stating those inputs cannot be checked. For a producer evaluating a proposal, asking which numbers were assumed is the fastest way to test whether the result applies to the operation in question.