Piglets.

2020-21 Rapid Ag: Evaluation of Biosecurity Procedures to Prevent Indirect Transmission of Senecavirus A

May 17, 2019

Principal Leader

Fabio Augusto Vannucci

Department

Veterinary Population Medicine

The Problem

Vesicular disease caused by Senecavirus A (SVA) is clinically indistinguishable from high-consequence foreign animal diseases, including foot-and-mouth disease (FMD). SVA infection became an emerging concern in the swine industry in 2015 when an increasing number of cases started been reported in large production systems. The disease is currently endemic in the swine population and the industry is continuously facing a false-alarm of FMD in a daily-basis due to the high similarities between vesicular lesions caused by SVA and FMD. Therefore, understanding the transmission routes by which SVA spreads among swine farms is critical to mitigate the disruption in the pork chain caused by this vesicular disease. Based on the applied problem-solving priorities of the Rapid Agricultural Response Fund, we are proposing to study the impact of biosecurity procedures on the transmission and spread of SVA among pig populations. Low, medium and high biosecurity procedures will be assessed under experimental conditions in order to investigate survival and transmission of SVA from fomites and personnel after contacting infected pigs. The information from this study will be essential to guide practical decisions focusing on reviewing, and potentially adjusting current biosecurity practices to prevent and mitigate SVA infections.         

Background

Based on the high similarities between vesicular lesions caused by SVA and other foreign animal diseases, differential diagnosis is critical and it has been specifically driven by the devastating economic impact of FMDV. Due to a restricted protocol followed by swine veterinarians for diagnostic investigations of vesicular diseases, the impact of the SVA infections has significantly affected both, public sector (i.e. Board of Animal Health, USDA, State Veterinary Laboratories), through the reallocation of resources for diagnostic investigation, and the private sector (i.e. producers and pork processing industry), through temporary closures of pork processing plants until the diagnosis of foreign animal diseases has been ruled out. This scenario has drawn significant attention from pork producers and official authorities due to potential compliances and decreases of diagnostic investigations for foreign animal in SVA cases, especially if the disease becomes endemic in swine herds. Others economic relevance for pork producers has been characterized by:

      • Hold and/or redirect market pigs to other processing plants due to closure for diagnostic investigation of vesicular disease.
      • Increasing culling rates and the additional costs associated with SVA elimination
      • Acute mortality of neonatal piglets
      • Increasing lameness and susceptibility to opportunistic bacterial infections finishing farms.

The present proposal is focusing on identify viable modes of transmission and spread of SVA within and between swine herds. Indirect transmission is the most worrisome to producers since it is hard to visualize and test for. Movement of contaminated materials, including personnel, can play a significant role in the spread of virus within and between farms. The biosecurity levels proposed (low, medium and high) include a combination (or lack) of changing of clothing, footwear, showering, hand washing and downtime procedures commonly used in commercial swine operations. We have successfully used the model proposed in this study to evaluate the indirect transmission of swine influenza virus and PEDv.

The information from this proposal will help quantify the risk of SVA transmission and to obtain relative information on the frequency of transmission under different levels of biosecurity. Information on the survival of the virus on fomites along with the investigation of human as a potential vector for indirect transmission will be critical to design and establish effective mitigation methods in swine systems. Lastly, the long term impact of the information from this study will be essential to prevent and reduce the spread of SVA and will allow swine operations to follow validated biosecurity protocols.

Objectives and Goals

The overall goal is to determine the impact of biosecurity procedures on the transmission and spread of Senecavirus A between pig populations. The study will address three specific objectives:

Objective 1: To evaluate the indirect transmission of SVA from infected pigs to sentinel pigs under low, medium or high biosecurity measures as a model to determine means of SVA spread between pig populations. Biosecurity categories:

    • Low: direct movement of personnel from infected to sentinel pigs.
    • Medium: change coveralls, boots, gloves and washing hands.
    • High: 24 hours of downtime, shower, and clean set of clothing.

Research question: Does the level of biosecurity procedures prevent or mitigate the indirect transmission of SVA between pig populations?

Objective 2: To assess the survivability of SVA in fomites (coverall, shirts, pants, boots, etc.)

Research question: Is SVA able to survive in fomites and play a role on the indirect transmission between pigs?

Objective 3: To investigate human as potential vector for indirect transmission of SVA.

Research question: Are humans able to carry and/or harbor SVA and play a role on the transmission of the virus between pigs?

References

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  3. Morrison, B. Swine Health Monitoring Program, College of Veterinary Medicine, University of Minnesota, 2017.
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