Feed is a fomite for swine viruses. These viruses not only cause significant animal welfare issues but also result in significant economic losses. Combating these viruses requires reviewing and strengthening your operation’s biosecurity program to block potential opportunities for transmission.
Biosecurity programs are systems designed to keep farms free of pathogens and resulting diseases. Swine disease outbreaks, such as PEDV, PRRS and ASF, remind us that it is always essential to understand how pathogens can enter production systems, oftentimes via transmission vectors referred to as fomites.
When developing on-farm biosecurity programs, producers typically assess the risk of pathogen entry onto farms by determining how, when and where a pathogen's introduction can occur. Accurately assessing risk requires the identification of possible fomites, methods by which fomites can become contaminated and enter the farm, frequency of fomite entry and potential for fomite to come into direct contact with livestock. From there, on-farm biosecurity plans, action items and personnel education programs are developed for fomites presenting the most significant risk of pathogen transmission.
For example, let's evaluate the risk associated with feed as a fomite for viruses causing swine disease by answering the following questions:
- Is feed a fomite for viruses? Several peer-reviewed studies have evaluated the survival of viral pathogens in animal feed ingredients or feed products. These studies confirmed that viruses can survive in feed matrices, ascertained that some feed ingredients or feed products present a better matrix for virus survival than others, and identified selected ingredient matrices seem to enhance virus survival. In an experiment designed to simulate transoceanic shipment, ASFV demonstrated a half-life in feed ranging from 9.6 to 14.2 days. In approximately two weeks, the total viable virus concentration would only decay by half its original count. Furthermore, feed has been identified as an infectious vehicle and a credible risk to biosecurity. Studies using real-world conditions to simulate virus transmission in feed confirmed PEDV and PRRSV recovery from contaminated feed and demonstrated that contaminated feed could cause disease among the herd. Similar studies looking at ASFV transmission via feed found that the infectivity of contaminated feed is heightened due to repeated exposure, or in other words repeated herd exposure to contaminated feed reduces the viral load required for infection.
- How does feed come onto farms? Feed is central and widespread within all animal production systems and present throughout the entire animal production cycle. Feed and feed ingredients are sourced and transported worldwide, coming from various climates and growing seasons. Tractors, trains, boats, trucks, flat stores, silos and feeders are all used to transport and store feed and are subject to subsequent contamination and possible secondary fomites. In turn, repeated feed exposure to these secondary fomites increases the risk of contaminating subsequent feed batches and increasing pathogen prevalence within the feed and food production chain.
- How frequently is feed brought onto the farm? Feed is delivered directly to farms and production animals daily. Feed touches everything, trucks, milling equipment, people and feeder lines, meaning it has widespread influence within multiple areas of animal production, primarily if the contamination occurs during the feed production stage.
- What are the chances that feed introduces viruses to livestock? Since feed is part of everyday animal production, the opportunity for contamination in feed to reach the herd is high. Suppose the contaminated feed is consistently fed to herds; even at a low level of contamination, the likelihood of swine disease increases. In addition, pigs are the target host for viruses such as ASF, PEDV and PRRS, so once the farm and pigs are reached, the odds of virus survival increase and the potential for host-to-host transmission occurs. Feed as a fomite significantly impacts animal production, performance and welfare because of its prominent role in swine production. Every operation has different needs and challenges. Contaminated feed has a massive impact because it touches all feeders in all houses and barns in every operation, large or small.)
Access the latest data on PEDv & PRRSv mitigation below.
