In a recently completed study funded by the Swine Health Information Center (SHIC), Daniel Linhares, DVM, MBA, PhD, from Iowa State University (ISU) and his colleagues reported on the number of production events in facilities of all sizes and production styles that had a direct impact on porcine reproductive and respiratory system (PRRS) outbreaks to help prioritize biosecurity practices. The study also compared biosecurity practices of herds with relatively low or high PRRS incidence within and between production systems. Because of the significant sample size, the project provides concrete data to help producers allocating investment in biosecurity, minimizing the risk of virus introduction.
The objective was to describe key differences in the biosecurity aspects of breeding herds with relatively low PRRS incidence, compared to those with relatively high PRRS incidence, so ongoing biosecurity assessments can be more efficient and take less time. This was a collaborative project between ISU, the University of Minnesota, and swine production systems. It included 14 production systems and 84 herds in 13 states across the US.
“One of the findings is that the number of events matter,” Linhares remarked. For example, if a system weans pigs every day versus once a week it makes a difference. The frequency of people exiting and re-entering the farm also has an effect. A higher number of events was associated with a higher frequency of PRRS outbreak. While Linhares acknowledges operations cannot avoid the entry of pigs and people, he said the study suggests efforts to organize the people and pig flows to reduce events would be beneficial.
Linhares says that full, comprehensive biosecurity assessments are necessary to characterize all risks for a given pig population. In addition to that, the dataset from this study will allow identifying the minimum number of questions that, when combined, gives a good correlation with expected frequency of PRRS outbreaks. This would allow producers to measure farm vulnerability to disease introduction more frequently over time.
Biosecurity aspects of each breeding herd were assessed using a 346 question survey, developed by Dr. Derald Holtkamp, ISU, containing questions about herd demographics, area swine density, PRRS outbreak history, frequency of risk events, and biosecurity practices related to swine transport, people movement, carcass disposal, supply deliveries, and other events. Results of the surveys from high and low PRRS incident herds were compared.
High PRRS incident farms had a higher monthly frequency of people entering and exiting the farm, in addition to higher frequency of pig movements. On-farm rendering was the production practice having the largest difference in frequency between low versus high PRRS incidence farms. The study summary gives additional information about area density, downtime and other differences between the two groups.
Per Linhares, the relative risk of PRRS outbreaks can be measured using “biosecurity scores” derived from questionnaires. Benchmarking the scores according to high impact outcomes, like those summarized in the report, may be a great tool for managers and producers to identify opportunities to reduce the vulnerability of their swine operations.
Swine Acute Diarrhea Syndrome Coronavirus (SADS-CoV), a coronavirus variant emerging in China, has been on the Swine Health Information Center’s (SHIC) radar and, based on information directly from China, new actions are being taken. Affected piglets show morbidity and mortality similar to the effects of PED, which reemerged in China in 2010. A recent letter to Nature reported on research about a 2017 SADS-CoV outbreak associated with neonatal piglet diarrhea and death in four Guangdong Province farms. In October 2017, the SHIC Monitoring and Analysis Working Group reviewed virus and outbreak information and advised continued monitoring of this virus to track spread. Communication with sources in China report the virus is continuing to move between farms and provinces, so SHIC is initiating preparedness research.
What SHIC Did to First Assess and Communicate SADS-CoV Risk in 2017
SADS-CoV was first identified in 2004 then again in 2006 in bats. First clinical signs in pigs were observed in late December 2016 and was associated with SADS-CoV in the first half of 2017. When this information was received, SHIC communicated the potential emergence of SADS-CoV in China to the US pork industry and asked the SHIC Monitoring and Analysis Working Group to review the outbreak information and advise on risk. The SHIC Working Group arrived at a consensus that SHIC should closely monitor the situation but not devote resources for diagnostics or to further investigate this virus unless there develops evidence of interregional spread in China, indicating this is more than an isolated incident. When contacts in China recently reported spread of SADS-CoV to three provinces, SHIC followed the Working Group’s recommendation to devote resources to evaluate need and, if necessary, develop diagnostics to increase US readiness.
What SHIC Is Doing Now to Ensure North American Readiness for SADS-Cov
The SHIC Preparedness and Response Working Group recently outlined a research strategy. An urgent call for proposals is being prepared. The call will focus on the development of diagnostic tools to facilitate the detection of this emerging virus should it travel to the US. The ability to detect this virus in clinical samples and in diagnostic tissues, and to detect antibodies to the virus in various tissues, including oral fluid samples, are priorities. SHIC also continues to research common inputs to US production with the objective of identifying potential pathways and preventing the entry of viruses, such as SADS-CoV.
What You Can Do Now
SHIC is encouraging swine veterinarians to increase awareness and understanding of SADS-CoV to help monitoring. The Chinese experience indicated a PED-like outbreak that continued and worsened with negative PED tests. Continue to be vigilant for unresolved high impact neonatal diarrhea and mortality that may warrant further investigation.
In incidents of high or ongoing morbidity or mortality, where an etiology is either not identified or there is a strong suspicion that the identified etiology is not the likely cause of the outbreak, SHIC continues to offer diagnostic fee support after the initial diagnostic workup is completed and paid for by the owner. In these cases, additional support for the fees of further diagnostic workup may help to identify newly introduced or emerging swine diseases. Find a description of the requirements, submission and review process for the Support for Diagnostic Fees program on the SHIC website.
Why This Virus Got the Attention and Research Funds of International Human Emerging Disease Experts
There were several reasons the 2017 bat-to-pig transmission caught the attention of human emerging disease investigation teams. First, the virus has a viral ancestor similar to human severe acute respiratory syndrome (SARS), which transmitted from horseshoe bats to humans and caused over 8,000 infections and 774 human deaths in 2002. Of note, no further human SARS cases have been detected since 2004. To date, six CoVs are known to infect humans, but only two have been linked to large fatal outbreaks: SARS and Middle East respiratory syndrome coronavirus (MERS-CoV).
Second, like SARS, it is suspected the SAD-CoV infecting pigs has the same horseshoe bat reservoir. And lastly, the pig outbreak was within 62 miles of where the SARS (severe acute respiratory syndrome) index case-patient lived.
It is important to note researchers did evaluate the potential zoonotic transmission of the virus. They found no evidence of enhanced infection or entry for SADS-CoV in cells expressing known human coronavirus receptors, suggesting that none of these receptors functions as a receptor for virus entry for SADS-CoV. Also, to further help determine the risk of SADS-CoV to humans, all 35 employees exposed to the virus were tested and none were positive for SADS-CoV exposure.
The work was a collaboration among scientists from EcoHealth Alliance, Duke-NUS Medical School, Wuhan Institute of Virology and other organizations, and was funded by the National Institute of Allergy and Infectious Diseases, part of the National Institutes of Health. The research is published in the journal Nature.
Reports of porcine epidemic diarrhea virus (PEDV) recently triggered a request for the Swine Health Information Center (SHIC) Rapid Response Program to help identify pathways of PEDV introduction on affected farms. SHIC initiated a response to test the program as well as provide assistance to affected producers, identifying high risk events resulting in the outbreaks.
Following the Rapid Response Team’s investigation into the PEDV affected farms, the National Pork Board (NPB) organized an interactive review of the investigations with the participating veterinarians to examine outbreak reports with outcomes and action items identified.
SHIC’s goal for testing the program includes exercising the system for future emerging or foreign animal disease response needs, learning what went well, identifying what can be done better, and discovering what work needs to be done to continue to support the process. During the NPB review, participants shared their observations about results of the farms’ investigations and the Rapid Response Team process. This SHIC-NPB collaboration helped to further develop the overall goal of building and maintaining industry preparedness in the event of an emerging or foreign animal disease outbreak.
The NPB executive summary of the review contains details on the investigation results. Risk events were subjectively assigned a risk level of low, medium or high likelihood for PEDV introduction by each investigation team. Risk events rated high most often included dead removal, weaned pig removal, cull sows and feed delivery. Areas of concern from the affected farms were listed along with recommendations for preventing further outbreaks.
Since November 25, 2017, there have been 10 Rapid Response Program investigations focusing on PEDV outbreaks on farms. Current PEDV outbreaks spanned from February 9, 2018, to March 6, 2018. All of the investigations occurred in commercial sow herds.
There has been a recent increase in cases testing positive for PRRS virus by rRT-PCR. The domestic disease monitoring project advisory group reached consensus that this is possibly due to a) increased use of processing fluid to monitor sow herds, and b) increased PRRS virus activity in grow/finish pigs. There has been a significant increase of processing fluids to test for PRRS virus on sow farms. This specimen was not reported in previous years, and in 2018 accounted for more than 5 percent of total the submissions at the participating VDLs for PRRS rRT-PCR testing.
Deltacoronavirus (PDCoV) activity continues high relative to predicted values based on previous years. There was a 19 percent increase in the number of Central Nervous System (CNS) cases in 2017 compared to 2016. Partial data for spring 2018 indicates a 30 to 40 percent increase in CNS disease compared to spring months of 2017. Streptoccocus suis has been the main pathogen associated with CNS disease.
The May Swine Health Information Center-funded domestic swine disease monitoring report PRRS data now includes information from the Iowa State University and University of Minnesota veterinary diagnostic labs. Work to integrate other disease information and laboratories into the report continues.
April saw the addition of Hungary as the seventh country in the EU now with ASF. It was found in a wild boar that was a considerable distance from known infected populations. Local authorities report the disease was probably introduced through infected food waste. Pig prices have plunged as external markets Serbia, Japan and South Korea have stopped importations of pigs and pork products.
The Swine Health Information Center (SHIC)-funded global swine disease monitoring system is initially being tested for the three tier-1 foreign swine diseases (ASF, CSF, FMD) with the expectation of expanding it to other relevant diseases of swine in the future. Effective this month, searches for porcine rotavirus, porcine epidemic diarrhea virus (PEDV) and Aujeszky’s disease/pseudorabies (suid herpesvirus 1 (SuHV1)) began. However, no relevant news item was identified for any of those diseases and we are still in the process of optimizing the searched for those pathogens.