As the world deals with the COVID-19 pandemic, SHIC continues to focus efforts on prevention, preparedness, and response to novel and emerging swine disease for the benefit of US swine health. As a conduit of information and research, SHIC encourages sharing of its publications and research. Forward, reprint, and quote SHIC material freely. SHIC is funded by America’s pork producers to fulfill its mission to protect and enhance the health of the US swine herd. For more information, visit https://www.swinehealth.org or contact Dr. Sundberg at [email protected].
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A study on porcine circovirus type 3 (PCV3) funded by the Swine Health Information Center (SHIC) mined diagnostic data obtained by the University of Minnesota Veterinary Diagnostic Lab (UMN VDL) during the last two years to identify associations between the presence of PCV3 and its viral load, and specific lesions and clinical conditions. Results from this study suggest PCV3 may cause death in fetuses and myocarditis and systemic vasculitis in pigs. PCV3 was discovered in 2016 in the US, associated with cases of systemic disease and reproductive disorders. Multiple studies performed during the last two years have shown that this virus is widespread and has been around for decades. It can be found in multiple tissues and samples, in pigs with multiple clinical conditions and in healthy pigs. However, a lack of precise information on the relevance of this virus and its potential to cause disease in pigs existed.
PCV3 results, clinical signs, and information on the lesions for each pig were retrieved from the UMN VDL lab information management system, submission forms, and diagnostic reports. PCV3 frequency in pigs with different clinical signs ranged from 12% to 27%. No significant associations were observed between clinical signs and the presence of PCV3. In PCV3-positive pigs, no clinical signs were significantly associated with having a higher load of PCV3. PCV3 frequency in pigs with different lesions ranged from 0% to 62%.
Even though this study did not identify any significant associations with clinical signs, the lesion that had a significant association between its presence and PCV3 infection was heart vasculitis/perivasculitis. In PCV3-positive pigs, higher viral loads were significantly associated with pigs with myocarditis, heart vasculitis/perivasculitis, kidney vasculitis/perivasculitis and dermatitis.
And the presence of PCV3 in 20% of cases involving fetuses is remarkable. The samples with the highest PCV3 concentration in this study were from fetal tissues and lesions of myocarditis and systemic vasculitis were associated with the presence or the amount of PCV3 in these tissues. The lack of significant results for other lesions does not exclude the possibility of a real association and may be due to confounding factors or limited data.
In summary, this study provides an objective view of the relationship between PCV3 and disease, based on a large dataset of diagnostic cases. PCV3 is a very common virus that circulates in healthy populations and can be detected in around 20% of the pigs submitted to the diagnostic laboratory. Therefore, it is important to differentiate when PCV3 plays a significant role and when it does not. The results from this study support previous studies that suggested that PCV3 may cause death in fetuses and myocarditis and systemic vasculitis in pigs.
Working with funding provided by the Swine Health Information Center (SHIC), Dr. Scott Dee and his team at Pipestone Applied Research have been studying the risk of virus movement in feed. Early work was all completed in the laboratory and confirmed the survivability of porcine epic diarrhea virus (PEDV) in feed as the vehicle for transmission and transport. More recently, Dr. Dee developed a demonstration project to reproduce the results found in lab studies under real world conditions. In the report summary, results indicated the presence of viable porcine reproductive and respiratory virus (PRRSV), Senecavirus A (SVA), and PEDV in both soy products, while viable SVA was recovered from all five tested feed ingredients. In contrast, survival was limited in the vitamins and amino acid ingredients.
While all results achieved in the lab setting were valid, Dr. Dee noted a need, particularly from producers and governmental agencies, for more information beyond a lab setting. “We wanted to expose the viruses to as many environments as possible in the continental US,” he explained. “This was like an actual commercial journey.” The current SHIC-funded project saw feed spiked with viruses loaded in containers on a truck and driven all around the US. The trip lasted 21 days, involved 107 hours of transport, and crossed 14 states, covering approximately 6000 miles. From Minneapolis to Iowa to Colorado to Texas, across the southern coast, up the eastern seaboard, and back to the Midwest, the trip exposed the virus-spiked feed to mountainous, western, gulf coast, eastern, and New England environments as well as Midwestern.
Upon the truck’s return to Minnesota, the feed samples were tested. SVA was found in every feed ingredient being evaluated. Dr. Dee noted this reflected what had been seen previously in the lab, that SVA – a surrogate of food-and-mouth disease – survives and is stable in feed ingredients. The results for PEDV and PRRS showed they survived in feed as well. This demonstration also confirmed lab results showing soy-based products being supportive of viruses; both organic and inorganic soybean meal were included and all viruses lived well in each. In the end, results from the lab were reproduced in real world conditions.
It is important to note this demonstration project was conducted with great care for the viruses included in the test ingredients. Samples were very well contained in boxes securely loaded in the trailer without risk for spills. There was no other cargo in the trailer and the only stops made were for fuel and overnight rest. “We wanted to protect the sanctity of agriculture,” Dr. Dee stated. “These were not foreign animal diseases. We talked to the Board of Animal Health director and USDA. If we were managing the demonstration as described, they were perfectly fine with it.”
The amount of feed in this demonstration was small – just 30 grams per test. This allowed for the entire quantity of feed to be tested at the conclusion of the journey so there were no false negatives. Because this was a proof-of-concept project, a larger scale demonstration is next on Dr. Dee’s agenda for this fall.
“We’re going to do this whole thing again in November, using one ton totes of organic and inorganic soybean meal,” he remarked. “We will get away from the 30 gram amounts and into a representative volume producers are dealing with all the time in tons.” When these ingredients return, sample testing will be completed. The same route, viruses, and feed products will be used. “This helps bridge the gap from lab to the real world,” Dr. Dee concluded. He anticipates the results helping people gain more confidence with evidence viruses can live in feed under a commercial shipping event.
A new variant of porcine sapovirus (SaV) was identified in 2019 and appears to be the first detection of a single porcine SaV infection in piglets with diarrhea in the US. On a farm with SaV, piglet diarrhea during the lactation phase resulted in smaller pigs at weaning, with piglets losing one to two pounds, a severe impediment during this phase. Piglet diarrhea had been an issue on this farm for two years, creating a significant financial cost. A study on SaV funded by the Swine Health Information Center (SHIC) is underway with results expected in August 2020. SHIC funded the study to help understand if SaV, which is included on the Center’s Swine Disease Matrix, is an emerging pathogen in the US and to develop necessary diagnostic tools. An abstract of the SaV study with initial observations is now available.
The abstract states porcine SaVs are genetically diverse and widely distributed in pig-producing countries. To date, eight genogroups of porcine SaV have been identified, and genogroup III (GIII) is the predominant type. Most of the eight genogroups of porcine SaV are circulating in the US. In the study, reports on detection of porcine SaVs in pigs at different ages with clinical diarrhea using next-generation sequencing and genetic characterization are included.
All seven cases in the study have porcine SaV GIII strains detected and one pooled case was found to have a porcine SaV GVI strain IA27912-B-2018, per the published abstract. Sequence analysis showed that seven GIII isolates were genetically divergent and formed four different lineages on the trees of complete genome, RdRP, VP1 and VP2. In addition, these seven GIII isolates had three different deletion/insertion patterns in an identified variable region close to the three prime end of VP2. The GVI strain IA27912-B-2018 was closely related to strains previously detected in the US and Japan. A 3-nt deletion in VP1 region of GVI IA27912-B-2018 was identified. The study showed genetically divergent SaVs of different genogroups are co-circulating in pigs in the US.
Abstract authors state future studies comparing the virulence of these different genogroups in pigs are needed to better understand this virus. New diagnostic tools will help to understand the incidence of sapovirus and its contribution to piglet diarrheatic syndromes. Then an additional step could be if surveillance and vaccine development are needed to monitor and control porcine SaVs.
The Swine Health Information Center (SHIC) Global Swine Disease Monitoring Report has provided near real-time information on swine diseases regularly since November 2017, included in SHIC’s monthly enewsletter, posted online on the SHIC website, as well as published using channels available to authors at the University of Minnesota Department of Veterinary Population Medicine. The project created and now maintains a public, private, academic partnership for its reporting. Initial funding for the program will soon end, however, the team at the University of Minnesota VPM is preparing a proposal for continued funding of the project after August 2020. Ideas for improvements to the content or timing of the Global Swine Disease Monitoring Reports and the program itself are welcome. Please email SHIC Executive Director Dr. Paul Sundberg with your comments.
This reporting system identifies hazards and subsequently scores them using a step-wise procedure of screening to identify issues that potentially represent a risk for the US. A combination of soft and official data is actively and passively collected and organized. Following successive screening steps in which data and information is modified, edited, corrected, and expanded in collaboration with USDA/APHIS CEAH and selected stakeholders, a report describing the outputs has been available to the public routinely. In addition to the three USDA-classified tier 1 reportable foreign animal diseases (FAD) of swine, African swine fever (ASF), classical swine fever, and foot-and-mouth disease, which represent the main content, reports for significant changes in the epidemiological situation of production diseases such as porcine reproductive and respiratory syndrome or Aujeszky’s disease, have been included.
The project has been successful in identifying and communicating a number of potential threats to the swine industry. In particular, the project came in time to collaborate with relevant stakeholders in collecting, organizing, critically reviewing, and communicating the expansion of ASF through Asia and Europe.
Since the inception of the project and through April 2020, 44 reports have been produced (monthly, bimonthly, and emergency), which represents a higher frequency compared to the initial project design, mainly in response to the ASF expansion in Asia and Europe. Currently, the three USDA-classified tier 1 reportable FADs of swine are included in the report, and comments regarding diseases listed in the SHIC matrix are also included when appropriate, considering the epidemiological context of the event. New sections have been included in the report, in which specific topics are developed in-depth to provide context and interpretation of the monthly events.
Porcine reproductive and respiratory syndrome virus positive cases in April were down over March per the most recent Domestic Swine Disease Monitoring Report (DSDMR) and within the forecasted levels for this time of the year. The DSDMR advisory group pointed out COVID-19-related packing plant shutdowns have led to the retention of animals in the field and caused negative market impact. They also noted this may affect the implementation of health interventions, as well as cause disruptions of pigs and people flows. Altogether, these factors can lead to increased pressure of pathogen infection in the field in the near term. Porcine epidemic diarrhea virus (PEDV) and porcine deltacorona virus (PDCoV) cases were also down in April compared to March. Both were in forecasted levels for this time of year. The overall percentage of Mycoplasma hyopneumoniae positive cases in April was within the forecasted levels, down from March levels.
In Poland, 450 farms in the province of Greater Poland have been placed into lockdown, involving over 30,000 pigs in total, due to African swine fever (ASF). Five Chinese provinces reported new ASF outbreaks since last year. Authorities said the risk of ASF has increased significantly as farmers rush to rebuild their herds. India reported its first outbreak of ASF in the state of Assam in northeastern India. There, over 2500 pigs have died across 306 villages. ASF in Papua New Guinea continues with authorities confirming the first outbreak in Southern Highlands province. The Australian swine industry remains on high alert.