New World Screwworm: Fact Sheet & SHIC Article 6/10/2026 & USDA NWS Website
New World Screwworm: Fact Sheet & SHIC Article 6/10/2026 & USDA NWS Website
To better understand disease risks associated with mortality management, the Swine Health Information Center’s Wean-to-Harvest Biosecurity Research Program, in partnership with the Foundation for Food & Agriculture Research (FFAR) and the Pork Checkoff, funded a study to determine whether swine pathogens can be detected around dead animal handling structures including dead boxes and composting bins. Led by Dr. Igor Paploski, University of Minnesota, the study tracked the presence of four major swine pathogens around structures to assess environmental contamination and the potential for pathogen spread. Researchers found that environmental contamination around mortality management areas was common on farms using both rendering and composting for carcass disposal, although contamination was more frequent around farms using rendering. Findings highlight that dead animal handling structures represent an important biosecurity risk and suggest that relatively simple management practices may help reduce environmental contamination, thus strengthening farm biocontainment and biosecurity.
Read the industry summary of project #24-076 here.
Key observations:
Rendering was associated with greater environmental contamination compared to composting.Vehicles and people may inadvertently transport environmental contamination from dead animal handling structures.Interventions such as whitewash may reduce environmental contamination on dead animal handling structures.Weather conditions such as rain can increase environmental contamination.Dead animal handling areas represent biosecurity risk areas, but also opportunities to reduce contamination.The study had four objectives: 1) assess environmental contamination surrounding dead animal handling structures on wean-to-market farms, 2) evaluate if a contamination-proxy compound could be mechanically transferred from these areas, 3) assess the effect of whitewash on reducing environmental contamination, and 4) identify farm practices associated with contamination levels around dead animal handling structures.
To conduct the study, a total of 40 PRRSV and/or PEDV positive wean-to-market farms were enrolled, including 20 that utilized rendering and 20 that utilized composting for mortality management. Ten environmental samples were collected per farm and tested by PCR for PRRSV, PEDV, PDCoV, and TGEV. Samples representing the ground near the structures, road, leachate, carcass, and the structure’s wall were collected. To determine if a viral proxy applied near a dead box could be detected in the vicinity of the farm or near a downstream dead box, Glo Germ was utilized as a marker for contamination. Glo Germ was applied on the road leading to the dead box on eight farms, and a car or a person was used to evaluate potential for movement of contaminated material.
Whitewash was also investigated as an intervention strategy through its application to the dead box of 10 additional farms that were potentially PRRSV and/or PEDV positive. To describe biosecurity and practices associated with dead animal disposal in wean-to-market farms and investigate their association with environmental viral contamination, questionnaires were administered to the 40 farms enrolled in objective 1 and results were used to stratify the environmental contamination findings. Farms were classified as environmentally contaminated or non-contaminated based on the detection of positive PCR results for viruses in environmental samples.
Results showed that environmental contamination was more frequently detected in farms using rendering (16/20; 80%) compared to composting (6/20; 30%) (p = 0.0015). The study found that farms that performed rendering were 5.4 times more likely to yield positive samples than composting sites, while recent precipitation increased the likelihood of environmental contamination. Specifically, the amount of precipitation during the seven days prior to sampling was positively associated with environmental contamination.
The quantity of viral genetic material detected in environmental samples also tended to be greater on rendering farms. Across all pathogens, positive samples from rendering farms had a mean Ct value of 30.8, while positive samples from composting farms had a mean Ct value of 33.6. Samples with the lowest Ct levels (highest viral genome quantity) were carcasses and leachates. While road samples were found positive, this sample type had fewer positive results comparatively. Overall, the environment surrounding dead animal handling structures on both rendering and composting farms frequently tested positive for pathogens known to be circulating within the herd.
Contamination of vehicles that drove over Glo Germ also occurred readily. In all six experiments, Glo Germ was detected on the vehicle’s wheels, mud guards, and undercarriage after driving through the treated area. After traveling 2 to 5 km to a neighboring farm, simulating the movement of a vehicle visiting multiple farms, Glo Germ could be detected both on the vehicle and on the road surface traversed immediately before reaching the destination farm. These findings demonstrate that vehicles can serve as potential fomites for pathogens, transporting material from the vicinity of dead animal handling structures to neighboring farm locations.
Glo Germ was applied to the road near the dead box, and a member of the research team, wearing disposable plastic boots, walked through the treated area before proceeding towards the farm office. Traces of Glo Germ were detected on the boots of the person, along the walking path, and near the entrance to the farm office, suggesting that personnel may inadvertently transport contaminants from the vicinity of dead animal handling structures even if wearing disposable plastic boots.
To investigate whitewash as an intervention to possibly diminish contamination around these structures, 10 additional farms were recruited, from which 10 environmental samples were collected from each farm, either from the ground immediately surrounding the dead animal handling structure or from the road leading to it. After sample collection, a whitewash solution was applied in the sampled area, and the farms were revisited two days later for post-treatment sample collection. On all collected samples, only PRRSV was found. The proportion of PRRSV-positive samples decreased from 13% to 3% after whitewash treatment with positive samples averaging a Ct value of 34.6. Results suggest that simple and inexpensive intervention measures, such as whitewash application, were associated with a substantial reduction in the frequency of PRRSV-positive environmental samples, indicating that practical mitigation strategies for contamination around these structures may exist.
Overall, dead animal handling areas represent biosecurity risk points and Dr. Paploski identifies opportunities for pork producers. The report recommends these areas should be treated as potential sources of contamination. Producers should ensure that mortality management structures are well maintained, properly designed, and used correctly. It is worth reviewing how carcasses are brought to the structure, if they are ever placed exclusively on the designated areas, and the structure’s overall condition. Also, having a line of separation, exclusive access routes for vehicles, unidirectional flow of carcasses and limiting unnecessary access to these structures may be beneficial.
The findings of this study highlight that dead animal handling structures represent a potentially important component of swine farm biosecurity. The consistency of the patterns observed across the objectives supports the hypothesis that dead animal disposal practices influence the accumulation and movement of pathogen-associated material in the farm environment. Future research should focus on determining the viability and infectivity of pathogens recovered from these locations, identifying which specific management practices contribute most to contamination, and evaluating interventions capable of reducing environmental contamination over longer periods.
Ultimately, improving our understanding of how dead animal handling structures contribute to disease epidemiology may provide new opportunities to strengthen biocontainment and reduce disease transmission risks within the swine industry.
Foundation for Food & Agriculture Research
The Foundation for Food & Agriculture Research (FFAR) builds public-private partnerships to fund bold research addressing big food and agriculture challenges. FFAR was established in the 2014 Farm Bill to increase public agriculture research investments, fill knowledge gaps and complement the U.S. Department Agriculture’s research agenda. FFAR’s model matches federal funding from Congress with private funding, delivering a powerful return on taxpayer investment. Through collaboration and partnerships, FFAR advances actionable science benefiting farmers, consumers and the environment.
Swine Health Information Center
The Swine Health Information Center, launched in 2015 with Pork Checkoff funding, protects and enhances the health of the US swine herd by minimizing the impact of emerging disease threats through preparedness, coordinated communications, global disease monitoring, analysis of swine health data, and targeted research investments. As a conduit of information and research, SHIC encourages sharing of its publications and research. Forward, reprint, and quote SHIC material freely. For more information, visit http://www.swinehealth.org or contact Dr. Megan Niederwerder at [email protected] or Dr. Lisa Becton at [email protected].