Leman: Contamination from animal disposal
Contaminants around dead animal structures represent a breach of biosecurity
25 February 2026
2 minute read
By: Editor's note: Following is a presentation by Rafael Melo and colleagues at the University of Minnesota, USA, during the 2025 Leman Swine Conference.
Swine mortality, particularly from infectious disease, poses biosecurity risks and makes it essential to dispose of cadavers in a biosecure manner to prevent disease spread. While transmission routes of swine viral pathogens are well studied, limited attention has been given to the role of dead animal disposal methods as sources of environmental contamination. External areas of farms are often shared by farm personnel, vehicles, maintenance crew, veterinarians, visitors, and crucially, equipment and machinery involved in dead animal removal. It is possible that viral contaminants around dead animal structures represent a breach to both successful biocontainment and bioexclusion practices.
A study assessed the environmental contamination around dead animal disposal structures and determined if the contamination differs according to how dead animals are managed.
Environmental contamination in dead animal management structures was assessed on 33 Midwestern US wean-to-market farms. Those farms were porcine reproductive and respiratory syndrome virus 2 (PRRSV-2) or porcine endemic diarrhea virus (PEDV) positive, according to their attending veterinarian. Ten environmental samples (two each from road, ground, wall, carcass, and leachate) from the vicinity of the dead handling structure were collected and PCR tested at the University of Minnesota Veterinary Diagnostic Laboratory. For PCR-positive farms, samples were sent for viral isolation.
Out of 33 farms (330 samples) tested, 18 (54.55%) tested positive for at least one of the tested viruses. When stratified by the dead animal handling method, 79.0% (15/19) of the rendering sites and 21.4% (3/14) of the composting sites tested positive for at least one virus. PRRSV-2 was the only pathogen identified at both rendering and composting sites. The average cycle threshold (Ct) value for PRRSV-2 positive tests was lower at rendering sites (30.4) compared to composting sites (33.6, T-test p-value= 0.012).
PEDV and porcine deltacoronavirus (PDCoV) were exclusively identified on 12.1% and 21.2% of the rendering farms, respectively. The Ct value for all pathogens tested was lower (suggestive of higher viral load) in samples collected from leachate and carcass, respectively. No successful viral isolates were obtained.
The results of the study indicate that dead animal handling structures in wean-to-market farms are frequently contaminated, and that environmental contamination was more prevalent on rendering sites.
Virus isolation was not successful from any of the environmental samples, suggesting that the detected viral material was either not infectious, not viable, present at levels below the analytical sensitivity of the isolation method, or contained inhibitors that hindered the isolation.
Despite this, the presence of viral genetic material in and around these structures supports the possibility of accidental transmission through contact with contaminated surfaces. Practices that minimize contact of carcasses or fluids originating from dead animal structures and commonly used farm areas, such as roads, may improve biocontainment near these sites.
