Introduction
African Swine Fever Virus (ASF) is a highly contagious pathogen causing hemorrhages and higher fevers with mortality rates that approach 100% (Ge et al., 2018). The recent fast spread of ASF across Russia, China, and Eastern Europe has heightened awareness of ASF and other World Health Organization reportable diseases as a threat to the United States (US) pork production (Dee et al., 2018; Guinat et al., 2016). An introduction in the US of Foot and Mouth Disease (FMD) or Classical Swine Fever (CSF) have a projected loss of $2.6-$14 billion (Dee et a., 2018; Paarlberg et al., 2009; Paarlberg et al., 2002). ASF introduction estimates to cause the US pork industry $15 billion revenue loss in the first two years and up to $50 billion over ten years (Carriquiry et al., 2020). Quick and effective methods for disease containment and elimination is a must to keep the financial burden of a new introduction of a Foreign Animal Disease (FAD) in the country to a minimum.
A diagnosis of a FAD like ASF in the US will evoke “stamping out policy” by which the goal is to eliminate an outbreak by the depopulation of all confirmed and exposed herds (World Organization for Animal Health, 2019). A successful depopulation to eradicate disease requires a means of disposing of infected carcasses in a manner that properly eliminates the virus to prevent further pathogen spread and exposure. FAD breaks in countries like the United Kingdom with FMD have shown the limitations of current carcass disposal methods (Wilkinson, 2007). An on-farm mass burial has legislative restrictions due to groundwater levels, burning presents public perception and human safety concerns, and the use of rendering facilities and landfills is troublesome due to the requirement of transporting infectious carcasses off-site (Scudamore et al., 2002; Wilkinson, 2007). Composting, however, is recognized as an environmentally friendly mortality management option for routine and emergency use in Australia, New Zealand, the US, and Canada (Guan et al., 2010; Wilkinson, 2007).
Studies on the degradation of swine viruses in compost material are limited, even for common industry viruses such as Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) and Porcine Epidemic Diarrhea Virus (PEDV). Traditional composting of covering full carcasses in a carbon source is commonplace for regular daily mortality. However, the method of grinding of carcasses (pre-processing) with carbon sources before windrow formation may be better suited for mass depopulation. Pre-processing requires less land space to complete than traditional compost. Pre-processing also shows a faster completion in the composting process than full carcasses with cattle, but limited information is available for swine (Erickson et al., 2004). Many compost studies are also done in temperature-controlled containers or buildings and not in the outdoor setting that mass composting would likely occur (Guan et al., 2010; Vitosh-Sillman et al., 2017). The ability to compost outdoors and achieve the required high composting temperatures are of particular concern in cold weather situations that exist during winter in the Midwestern US, where the majority of the countries pork production exists (Oppedahl, 2020). The risk of environmental contamination and the spread of viruses is a concern for carcass disposal in FAD eradication events for which little information is available for swine viral pathogens. Thus the objectives of this study were to analyze environmental contamination risk of pre-processing of swine carcasses, ensure required temperatures to kill FAD swine pathogens in compost under cold weather conditions, and to monitor the ability of compost to denature common swine viruses.