2.2 Information sources
The search for the papers started on Nov 16, 2018, after all the relevant records from the literature had been collected. MEDLINE and Centre for Biosciences and Agriculture International (CABI) databases were searched from 1864-2018 using the Iowa State University (ISU) Web of Science interface. The country of investigation and year was not used as exclusion factors.
The Swine Information Library (SIL) enables access to the Journal of Swine Health and Production (JSHAP) journal, American Association of Swine Veterinarians (AASV) Annual Meeting Proceedings (1999-2019), the International Pig Veterinary Society (IPVS) Congress proceedings (2000-2016), James McKean (formerly known as Iowa State University) Swine Diseases Conference proceedings (1996-2018), and the Allen D. Leman Swine Conference proceedings (2007-2018). These dates were dictated by the availability of electronic versions. We also searched the following relevant conference proceedings: American College of Veterinary Pathologists (ACVP) conference (2012-2018) and American Association of Veterinary Laboratory Diagnosticians (AAVLD) conference (2017-2018).