More than 230 Senecavirus outbreaks have been confirmed after July 2015 in the United States and this is why it is important:
“The clinical signs in pigs infected with vesicular disease caused by SVA are variable and can range from no outward signs, to nonspecific signs such as decreased appetite or fever, or pigs may develop vesicles, or blisters, on the skin or in the mouth.[..]
While SVA continues to plague U.S. and global pork producers, it is important to be reminded of and understand some basic characteristics and behavior of this virus. SVA causes vesicular lesions affecting the skin, mouth and feet of pigs of all ages and has been associated with increased neonatal mortality which may be accompanied by neonatal diarrhea. If vesicular disease is present, your state animal health official must be notified in order to rule out other foreign animal diseases, such as FMD. The virus can be detected in multiple sample types but there is variability in the amount of time for which each sample type can be used for detection. Finally, SVA is extremely stable and contaminated facilities, transport vehicles and fomites are concerns for possible virus transmission but several disinfectants have been shown to be effective at neutralizing the virus.”
This is our Friday rubric: every week a new Science Page from the Bob Morrison’s Swine Health Monitoring Project. The previous editions of the science page are available on our website.
Monitoring antimicrobial resistance is a research topic of utmost importance in the swine industry. Dr. Julio Alvarez at the University of Minnesota is leading some of this effort and this week, his team is presenting the latest results regarding Salmonella antimicrobial resistance in the strains isolated by the University of Minnesota – Veterinary Diagnostic Laboratory between the years 2006 and 2015 and the emergence of a new serotype S.4,[5],12:i:-
Key Points
Swine is the reservoir most commonly associated with the S.4,[5],12:i: serotype.
The prevalence of S. agona and S. 4,[5],12:i:- in isolates of swine origin recovered from clinical samples received at the Minnesota Veterinary Diagnostic Laboratory (MVDL) in 2006-2015 has increased.
In these serotypes an increased proportion of isolates were resistant to ceftiofur and enrofloxacin, compared with other serotypes.
The increase in the frequency of isolation of the S.4,[5],12:i:- serotype in humans may be paralleled by a similar increase in swine clinical samples received in the MVDL.
The information synthesized in the figure below is the evolution, over the years, of the percentages of Salmonella isolated at the UMN – VDL, belonging to each of other the following serotypes: typhimurium, agona, derby, typhymurium var5, and 4,5,12:i:-. The increase in the proportion of S.4,5,12:i:- can be seen starting back in 2011-2012.
How long do sows and piglets shed Senecavirus A after a clinical outbreak? How long is the viremia? Those are the questions answered in this case study of a Senecavirus A outbreak in one US farm.
Objective and Methods
Senecavirus A is a challenge for producers and veterinarians because of its clinical similarity to Food and Mouth Disease (FMD). In this study, 34 sows and 30 individual piglets from 15 different litters were sampled at day 1 post-outbreak and later at 1, 2, 3, 4, 6, and 9 weeks post-outbreak (PO). Serum, and tonsil, rectal, and vesicular swabs were collected for all of the pigs included in the study. The objective of the study was to explore the viremia and shedding patterns in those infected animals. All samples were submitted to the University of Minnesota, Veterinary Diagnostic Laboratory to be tested by PCR.
Percentage of serum (a), tonsil swabs (b), and rectal swabs (c) positive for Senecavirus A. Clinical outbreak happened in sow farm 1 (S1) and piglets from sow farm 2 (S2) were mixed with piglets from S1 at weaning.
Results
Vesicular lesions were seen in sows only for 2 weeks and had the highest amount of virus. In sows, the detection of Senecavirus A in tonsil and rectal swabs was greater than 90% at 0 week PO and remained as high as 50% through 5 weeks PO. Generally, viremia was detected up to 1 week PO in sows but it is important to note that viremia was not detected in 11 out of 34 (32%) of the sows at any point during the study. Viremia was detected in 18 out of 30 (60%) and 19 out of 30 (63%) in the suckling piglets from site 1. Similar to sows, viremia was not detected in 9 out of 30 (30%) of the site 1 piglets enrolled in the study.
The detection of Senecavirus A in sows tonsil swabs peaked 1 week PO (94% positive) whereas it peaked at day 1 PO for piglets (83% positive). The detection of virus shedding decreased over time in sows and piglets, and a single sow and piglet tested positive at 9 weeks PO.
The peak of Senecavirus A detection from rectal swabs in sows (91%) occurred at day 1 PO and continued to steadily decrease and was not detected at 9 weeks PO. In site 1 piglets, the detection of SVA peaked at 1 week PO (90% positive). 64% of the rectal swabs were positive at 4 weeks PO in site 1 piglets. At 6 weeks PO, the detection of Senecavirus A was same for both site 1 and 2 piglets (11%); however, a single piglet from site 1 was still shedding SVA at 9 weeks PO.
Discussion
The study assessed the shedding pattern of SVA in sows and piglets during an outbreak on a farm in the US and investigated the spread of SVA between pigs during the post weaning period. Vesicular lesions were seen in sows only for 2 weeks and had the highest amount of virus. In sows, the detection of SVA in tonsil and rectal swabs was greater than 90% at 0 week PO and remained as high as 50% through 5 weeks PO, these sample types should be collected and submitted, in addition to vesicular lesion swabs and fluid (if present), as part of FAD investigations for the detection of SVA.
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Abstract
Background: The study highlights the shedding pattern of Senecavirus A (SVA) during an outbreak of vesicular disease in a sow farm from the South-central Minnesota, USA. In this study, 34 individual, mixed parity sows with clinical signs of vesicular lesions and 30 individual piglets from 15 individual litters from sows with vesicular lesions were conveniently selected for individual, longitudinal sampling. Serum, tonsil, rectal, and vesicular swabs were collected on day 1 post outbreak, and then again at 1, 2, 3, 4, 6, and 9 weeks post outbreak. Samples were tested at the University of Minnesota Veterinary Diagnostic Laboratory for SVA via Real Time Polymerase Chain Reaction (RT-PCR)
Results: In sows, vesicular lesions had the highest concentration of SVA, but had the shortest duration of detection lasting only 2 weeks. Viremia was detected for 1 week post outbreak, and quickly declined thereafter. SVA was detected at approximately the same frequency for both tonsil and rectal swabs with the highest percentage of SVA positive samples detected in the first 6 weeks post outbreak. In suckling piglets, viremia quickly declined 1 week post outbreak and was prevalent in low levels during the first week after weaning (4 weeks post outbreak) and was also detected in piglets that were co-mingled from a SVA negative sow farm. Similar to sows, SVA detection on rectal and tonsil swabs in piglets lasted approximately 6 weeks post outbreak.
Conclusion: The study illustrates the variation of SVA shedding patterns in different sample types over a 9 week period in sows and piglets, and suggests the potential for viral spread between piglets at weaning.
This is our Friday rubric: every week a new Science Page from the Bob Morrison’s Swine Health Monitoring Project. The previous editions of the science page are available on our website.
This week, we are talking about Secure Pork Supply (SPS).
The goal of SPS is to develop procedures that pork producers, processors, and Federal and State agencies all agree are feasible to allow for the safe movement of animals from farms in an FAD Control Area to harvest channels or other production sites as long as they have no evidence of disease.
Key points
In the event of a foreign animal disease (FAD) outbreak in the U.S., maintaining business continuity for the pork industry is critical for food security and animal health and well-being.
The goal of the Secure Pork Supply (SPS) Plan is to provide a workable business continuity plan.
Having the SPS Plan in place prior to a FAD outbreak will enhance coordination and communication between all parties and speed up a successful FAD response.
Bob was a dedicated advocate for the swine industry, passionate about doing relevant work that will help producers. Man of the utmost integrity, he was a leading force in our world, striving to get better every single day. Bob was also the coordinator of the Allen D. Leman swine conference for many years and even if he was not seen walking down the hallways of the St. Paul RiverCentre, his presence was heavily felt throughout the four days of the conference. Around 1,000 participants gathered from all around the world to attend this annual event designed to provide science-driven solutions to problems encountered on swine farms.
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At the opening of the conference, both Dr. Trevor Ames, Dean of the College of Veterinary Medicine at the University of Minnesota and Dr. Gordon Spronk, lifelong friend of Bob, honored Bob’s memory and urged the swine industry to continue his legacy.
On Monday, Gary Louis and Dr. Luc Dufresne from Seaboard Foods gave a keynote lecture on their perspective of what it means to pursue initiatives for the greater good as an integrator whereas Dr. Bob Thompson received the Leman Science in Practice award and shared his experience and advice with young practitioners during the Breakfast Conversations. A lot of high quality research posters were displayed during the reception sponsored by Tonisity and some of our graduate students were among the six selected as best poster presentations.
The new DVM student session showed us that the next generation of veterinarians is curious, passionate about the swine industry and eager to solve its challenges. We will continue this session and enhance it with the creation of the Morrison Swine Innovator Prize which was unveiled during the Science in Practice reception sponsored by Boehringer Ingelheim.
On Tuesday, the keynote session was centered around coopetition, or the act of cooperating with your competitors as Rebecca Liu from Lancaster University explained. Dr. Noel Williams from Iowa Select Farms and Dr. Joel Nerem from Pipestome Systems both gave their perspective on how coopetition works in the swine world. One of the example mentioned was the Morrsion Swine Health Monitoring Program (MSHMP), a project Bob was passionate about, which allows producers to share information such as disease status and work together towards better swine health for all participants.
Most importantly, we would like to thank all of you for your continuing support. The Allen D. Leman swine conference would not exist without you and we hope to see you next year: September 15-18, 2018.
