CategorySwine Health - General Disease
Date Full Report Received12/06/2019
Date Abstract Report Received12/06/2019
Funded ByNational Pork Board
Introduction: Senecavirus A (SVA) is an emerging viral agent that has been associated with vesicular disease and neonatal mortality in swine herds in different countries. However, the greatest concern is the clinical similarity to other important vesicular diseases that can also affect pigs: Swine Vesicular Disease, Vesicular Stomatitis, Vesicular Exanthema of Swine and most importantly Foot-and-Mouth Disease (FMD). The United States swine industry has had increasing number of SVA reports in the last decade which prompts the question regarding how widespread SVA is this virus in the industry together with which factors are contributing to its occurrence. Therefore, there is a need to further understand the basic epidemiology of SVA.
Objectives: 1) Estimate the prevalence (proportion) of sites (breeding and growing pigs) with anti-SVA antibodies and 2) Determine herd-level risk factors associated with the presence of anti-SVA antibodies.
Methods: Pig producing companies and swine practitioners were invited to participate in this study. Herds were randomly selected based on willingness to participate. A total of 30 blood samples from each farm were collected and tested for SVA antibodies using an indirect immunofluorescent antibody test (IFA) at the University of Minnesota Veterinary Diagnostic Laboratory. For sow herds, blood samples were collected across parities and for finishing herds, blood samples were collected from pigs 20 weeks or older. The number of positive samples needed to classify a herd as positive was calculated. A questionnaire was used to record farm level characteristics that were used in the analysis to explore associations between seropositivity and risk factors.
Results: A total of 5,762 blood samples from 192 farms from 16 states were collected and tested for SVA with 268 (4.7%) samples yielding a positive result. Twenty-four herds (12.5%) had at least one positive sample out of which 17 and 7 were sow and finishing sites, respectively. There was significantly higher proportion of sow herds testing positive when compared to finishing sites. There were positive sow and growing pig farms located in 6 and 5 states, respectively. The average number (standard deviation) of positive samples in positive farms was 10.2 (9.8) and 13.4 (11.3) for sow and finishing farms, respectively. When the number of positive samples used to classify herds was increased to 2, only 1 farm was reclassified as negative. A total of 150 surveys have been received for a response rate of 78%. Factors such as rendering, farm type, number of biosecurity measures in place were positively associated with SVA status.
Discussion: Based on the findings of this study, antibodies to SVA are difficult to find which would suggest that the virus remains at a low prevalence in the industry. Even at a low prevalence, the virus continues to transmit as antibodies were found in farms located in different states and belonging to different production systems.