Whilst this report focuses on control measures for produces, results and suggestions may be of use to customers when assessing suppliers.
According to this expert panel, the most important preventive measures for commercial, non-commercial, and outdoor farms were the identification of animals and farm records; enforcement of the ban on swill feeding; and containment of pigs to not allow contact with pigs from other farms, feral pigs, or wild boar or their products. In addition to this, other measures were considered relevant in preventing ASF introduction, namely education of farmers, workers, and operators; no contact between farmers, farm staff and external pigs; appropriate removal of carcasses, slaughter residues and food waste; proper disposal of manure and dead animals, and abstention from hunting activities for a period of 48 h prior to any contact with domestic pigs. Finally, all experts considered important to facilitate and promote the access of veterinarians and health services to non-commercial and outdoor farms
From a Google it seems ASF detection kits do exist. I can't comment though on effectiveness or cost-benefit to your operation.