“ASF will likely be endemic by the time we identify its introduction.” That was a statement made by the US Department of Agriculture (USDA) during a recent African swine fever (ASF) working group call. Although probably accurate, it was a little disheartening to hear it stated out loud. It is a statement of recognition of something we all already suspected - the swine industry is likely to have a huge problem on its hands from the start of an ASF outbreak.
That realization highlights the need to identify an ASF virus introduction as quickly as possible. The speed with which we identify those early cases depends on the robustness and effectiveness of the surveillance strategy in place prior to the outbreak. That strategy relies on two key factors: 1) the ability to detect the virus in samples submitted to the veterinary diagnostic laboratories (VDLs) as part of the routine USDA ASF surveillance program and 2) our ability to observe signs consistent with ASF in the field and report those observations to the appropriate animal health officials. The first factor operates mostly behind the scenes and routinely analyzes case-compatible samples submitted to the VDLs from a variety of resource streams. It is designed to work regardless of whether the submitter suspects ASF, and functions largely without relying on the observational skills of producers or veterinarians. It is the second factor I want to talk about in this article.
Much of our hopes to diagnose ASF as early as possible rely on the ability of producers and veterinarians in the field to observe something out of the ordinary and react to it. I have no doubt that any one of us that suspected they were facing a case of ASF would immediately reach out to the appropriate animal health official and report our suspicions. What worries me is that I am not sure we consider ASF as a possible cause for the oddities we see every day.
For months, I have participated in working group calls aimed at enhancing our ability to detect ASF in the field. All those efforts are based on people in the barns recognizing something is different from normal and reporting it. But, what is “normal” versus “different?” We all know that there is significant variability between farms, barns, groups, genetics, seasons, etc when evaluating production parameters like morbidity and mortality. Veterinarians and producers are busy people. “It’s probably just PRRS or influenza and I really need to get home at a reasonable time tonight. I’ll check on them tomorrow.” How do you know when to pull the trigger and call the state or federal animal health official?
I understand that routine variability means that the folks in the field must make judgement calls. What is worrisome to me are the times we hear about very dramatic shifts in the norm and still no one reports it. Just recently, we have heard reports of significantly elevated rates of condemnations at a packing plant but no notification to the folks responsible for tracking disease for weeks. In another instance, high levels of mortality were observed in multiple barns in the Midwest without any report to animal health officials or initiation of a foreign animal disease (FAD) investigation. Fortunately, neither of these turned out to be an FAD but that is hindsight and exactly why ASF will be endemic upon detection.
If we are serious about doing everything we can to minimize the impact of an FAD introduction, everyone in the production chain must stop being afraid to report something abnormal. The USDA should be doing a lot more FAD investigations than they are currently doing. According to data on the USDA ASF/CSF Surveillance website, the Animal and Plant Health Inspection Service only conducted 27, 48, 32, and 53 swine-focused FAD investigations in Fiscal Years 2019, 2020, 2021, and 2022 respectively.1 Since June 1, 2019, only 8190 specimens have been submitted to the VDLs from commercial herds as part of the ASF/CSF Surveillance Program.1
Those numbers are way too low. Do the math – an average of 40 investigations since 2019 on over 60,000 swine farms and only 8190 specimens from more than 330 million hogs marketed. Is that really the best we can do and claim to be concerned about finding that first case? Observational surveillance can be, and must be, a significant and effective tool in the surveillance strategy. Remember porcine epidemic diarrhea virus? It was a veterinarian in the field who was willing to stand up and ask the questions about why things were different that called attention to that outbreak. Everyone who sees pigs in the field must be empowered to raise the alarm when there are suspicions that things just aren’t “normal.”
Harry Snelson, DVM
Executive Director
Reference
*1. US Department of Agriculture. ASF & CSF Executive Summary. Accessed May 31, 2022. https://www.aphis.usda.gov/aphis/dashboards/tableau/asf-csf-exec-summary-dashboard
* Non-refereed reference.