SHIC Wean-to-Harvest Biosecurity: Investigating Novel Farm Entry Systems

A study funded by the Swine Health Information Center Wean-to-Harvest Biosecurity Research Program, in partnership with the Foundation for Food & Agriculture Research and Pork Checkoff, assessed the development of an effective and practical biosecurity entrance system. Led by Dr. Teng Lim at the University of Missouri, various biosecurity interventions were evaluated for their effectiveness, including air showers, disinfectant spraying, disinfectant fogging, and their combinations, on reducing bacterial and viral contamination of cloth, skin, and hair surfaces. While full-body showering was confirmed as the most effective method, a system combining air showers with disinfectant spraying and hair nets performed similarly, revealing opportunities and challenges with novel methods. 

Find the industry summary for Swine Health Information Center project #23-049 here. 

Traditional biosecurity measures such as shower-in/shower-out and Danish entry systems (DES) are effective but can be difficult to consistently implement due to time requirements and compliance by farm personnel. Farm-specific coveralls and human hygiene are critical barriers to pathogen entry. However, overlooked aspects such as worker hair, clothing, and dirty hands remain significant reservoirs for pathogen transmission. Human hair is a naturally shedding material that can carry and release pathogens when not properly covered with hair nets or sanitized through physical (showering) or chemical means. Since a single lapse in protocol can lead to pathogen introduction, developing alternative or supplemental methods that are practical, efficient, and acceptable to workers is essential. 

Objectives of this project were to evaluate a combination of innovative biosecurity-effective entry systems for commercial pig farms as replacement options for the strenuous shower-in and shower-out system. The study was designed to evaluate the effectiveness of multiple biosecurity interventions—including air shower (AS), disinfectant spraying (DS), disinfectant fogging (DF), and their combinations—with and without integration of the DES and hair nets (HN). Another treatment was the Modified-DES (MO.DES), which was the DES but instead of hand washing, it utilized hand sanitizer. Three representative surfaces, including coverall or t-shirt, leather or pigskin (representing human skin), and faux fur (representing human hair), were contaminated with two bacteria, Staphylococcus aureus (Gram-positive) and Escherichia coli (Gram-negative), and two viruses, canine distemper virus (CDV, enveloped) and feline calicivirus (FCV, non-enveloped), to assess the efficacy of the treatment methods. 

A commercial AS unit was installed for personnel decontamination. For the DS and DF components, a 7-ft × 4-ft outdoor storage shed was repurposed as a dedicated chamber for disinfectant application. Slightly acidic electrolyzed water (SAEW) was used as the disinfectant and was prepared at available chlorine concentrations of 50, 100, 200 and 300 mg/L. SAEW was generated by electrolyzing tap water with a brine/electrolyte solution containing 107 g NaCl and 40 mL of 12 M HCl in 500 mL distilled water, using a commercial electrolyzed water generator.  

Two entry protocols were evaluated: the Danish entry system, which involved the use of hand soap, farm-specific clothing, and dedicated footwear; and the modified Danish entry system, which used hand sanitizer and hair nets in addition to farm-specific clothing and footwear. Treatments were tested with and without the Danish entry system, hair nets, and a modified Danish entry system using hand sanitizer.  

For the evaluation of bacterial load reduction, standard plate count methods were used to evaluate the effectiveness of the individual and/or combined treatment systems in reducing E. coli and S. aureus contamination from cloth, skin, and hair surfaces. For the viral load reduction test, cycle threshold (Ct) values were measured using real-time PCR on samples recovered from control and treated sample surfaces, and were evaluated for the effectiveness of the individual and/or combined treatment systems. 

Overall, results demonstrated that while the single-step methods including air showers, disinfectant spraying, and disinfectant fogging were largely ineffective on their own, integrating the Danish entry system or hair nets significantly enhanced both bacterial and viral reductions. The bacterial reduction study (E. coli and S. aureus) revealed that disinfectant spraying and air showering with disinfectant spray achieved over 2-log reduction, while Danish entry system or hair net-enhanced combinations reached 3–4-log reductions. While the full shower remained most effective, particularly for hair (5-log reduction), the air shower plus disinfectant spray plus hair net treatment performed similarly. The modified Danish entry system eliminated bacteria to undetectable levels on hands. Across all treatments, E. coli exhibited consistently higher susceptibility to treatment than S. aureus. 

For the viral reduction tests (FCV and CDV), only Danish entry systems or hair net-based combinations achieved meaningful reductions, with two combinations performing close to the full shower protocol:  

1) air shower, disinfectant spray and Danish entry system 

2) air shower, disinfectant spray and hair net  

Incorporation of Danish entry system markedly increased viral Ct values (higher Ct values indicate low viral load), with mean Ct values above 35, significantly higher than controls and single-step treatments. Combinations containing Danish entry system, particularly air shower plus Danish entry system, disinfectant fogging plus Danish entry system, and the combination of air shower, disinfectant spray and Danish entry system, produced Ct values >35 with several undetectable replicates, representing significantly greater viral reduction than all non-Danish entry system treatments.  

Overall, results of this study demonstrate that Danish entry systems and hair nets are critical additions for effective microbial control during farm entry. Further, the use of an alcohol-based hand sanitizer as part of a modified Danish entry system and multi-step combinations can offer practical, effective alternatives in settings where full-body showering is not feasible. 

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 US Department of 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. Connect: @FoundationFAR