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].
All are invited to a webinar on coccidiosis in swine being held tomorrow, September 3, 2020, from 1:00 – 2:30 pm CT. Jointly sponsored by the Swine Health Information Center and American Association of Swine Veterinarians, the webinar will include Drs. Jeremy Pittman, Smithfield, and Amber Stricker, Suidae Health & Production, sharing their experience with coccidiosis including management design, strategies, and interventions. Dr. Kent Schwartz, Iowa State University Veterinary Diagnostic Lab, will share clinical presentation and diagnostic information. And Dr. Robert Friendship, University of Guelph, Ontario Veterinary College, will provide a Canadian perspective as well.
SHIC 2020 Webinar Series
SHIC is offering a series of webinars. The October 2019 viral myelitis webinar was recorded and is available on the SHIC website for review. A webinar on hemorhagic tracheitis was held on April 2, 2020, providing information on the syndrome, its signalments, tissues for postmortem assessment, and management. The intent of the webinars is to inform practicing veterinarians about current swine health issues. The plan is to respond in a timely manner to questions and cases practitioners face, providing resources as well as other veterinarian’s discussion and experience. If you have ideas for webinars, please share those with SHIC Executive Director Dr. Paul Sundberg by emailing [email protected].
Availability of a highly sensitive and specific polymerase chain reaction (PCR)-based diagnostic assay for rapid differential detection of pseudorabies virus (PRV) variants, such as those now endemic in China, is critical to prevent huge economic losses to the US and Canadian pork industries if these strains enter North America and cause an outbreak. A single-tube triplex real-time-PCR assay for differential detection of variant strains of PRV has been developed and evaluated in a project funded by the Swine Health Information Center (SHIC) and Canadian Food Inspection Agency (CFIA). The triplex real-time PCR assay developed in this project could be used as a rapid diagnostic tool for foreign animal disease detection in North America or for surveillance and in epidemiological studies in countries, like China, where both classical and variant strains are endemic. The assay is also able to differentiate wild-type PRV from the gE-deletion PRV mutant marker vaccines.
In response to questions posed by the National Pork Board prior to 2015, the National Veterinary Service Lab tested the ability of PCR tests available at that time in the US to detect the Chinese PRV high pathogenic variant. They found the US PCRs can detect it if it gets to this country. Now, this new triplex enhances that capability by being able to differentiate the Chinese PRV from the classical strains of PRV as well as from the vaccine strains of PRV.
The newly developed assay targets the intergenic region between the US2 and US6 genes in the PRV genome. It is highly sensitive and specific and did not detect other non-target viruses including related herpesviruses. The clinical specificity and sensitivity of the assay was evaluated using whole blood, serum, tissue, and swab samples collected from known negative and experimentally inoculated pigs with either classical (Bristol) or variant (JS-2012 and HeN1) PRV strains. The targeted genomic region of this assay is also deleted in commonly used PRV gE-deleted marker vaccines, and therefore, the triplex assay did not detect viral DNA extracted from two commercial vaccine strains Bartha K-61 and Bucharest. This single-tube triplex assay can be used for routine diagnostics and epidemiological studies for detection and differentiation of classical strains from variant strains of PRV, and as a differentiation of infected and vaccinated animals (DIVA) assay when PRV gE-deletion mutant marker vaccines are used.
When compared to virus isolation, the gold standard for PRV diagnostics, the real-time triplex assay was equally sensitive in most of the samples, excepting two of the three trigeminal ganglia samples which tested positive by triplex real time PCR assay but were negative by virus isolation. This could be due to rapid establishment of latent stage by these viruses in trigeminal ganglia in these two animals. However, this could also indicate that the triplex real-time PCR assay is more sensitive than the virus isolation method for PRV detection.
PRV causes Aujeszky’s disease or pseudorabies (PR), fatal encephalitis in newborn piglets, respiratory infection in growing and fattening pigs, and reproductive failures in pregnant sows. It establishes a lifelong latent infection in the peripheral nervous system followed by subsequent intermittent shedding of infectious virus. Since 2011, highly virulent PRV strains that are genetically different from the classic PRV strains surfaced in pig herds in China.
For pigs left in the barn after a load-out event, viral contamination may be transferred from the contaminated livestock trailer, driver, or other carrying agents. Questions about how frequently this occurs, or alternative biosecurity measures to reduce frequency, remain. Consequently, the Swine Health Information Center (SHIC) funded a study conducted by personnel from Iowa State University to try to objectively assess these issues. The study evaluated if implementing a staged loading procedure for market pigs is effective at preventing transfer of swine pathogen contaminated particles from livestock trailers to the barn using fluorescent powder (Glo Germ) as a marking agent to be able to see traffic patterns. The study compared a conventional method of loading and a staged loading procedure. Four out of the five measuring points in the center alleyway of the barn had a level of contamination that measured significantly lower (p<0.05) for the staged loading protocol compared to the conventional loading protocol.
In standard loading protocols, there is usually only one line of separation between the livestock trailer and the end of the load-out chute. Load-out crew members cannot cross over this line into the livestock trailer and the driver cannot cross over onto the chute. In a staged loading protocol, a second line of separation is implemented. One member from the load-out crew is stationed between the two lines of separation in which he or she cannot cross onto the livestock trailer or cross the second line of separation into the center alleyway of the barn. The remaining load-out crew members within the barn cannot cross the second line of separation into the load-out alleyway or chute. In the study, there were 10 replicates per loading procedure.
During the study, Glo Germ was mixed with obstetric gel and dry wood chips in a large plastic bag and spread evenly on the floor of the livestock trailer, just inside the roll-up door opening to the chute. Load-out was observed and when completed, Glo germ contamination was evaluated using a grid of eight different measuring points within the chute after the first line of separation, two within load-out alleyway before the second line of separation, and five within the center alleyway.
The staged loading procedure completely eliminated contamination within the center alley measurements in one replicate, but, did not completely eliminate contamination in all other replicates. Four out of the five measuring points in the center alleyway of the barn had a level of contamination significantly lower (p<0.05) for the staged loading protocol compared to the conventional loading protocol. The difference at the fifth measuring point in the center alleyway of the barn was nearly significant (p=0.0573). The level of contamination measured at all other measuring points, in the chute and load-out alleyway, were not statistically significant between the two study groups.
Further research will follow-up on this proof of concept. Work to develop an objective evaluation of swine health as affected by conventional vs. staged loading is underway.
The need to quickly identify, control, and eliminate a pathogen in an endemic, emerging, or transboundary production disease outbreak in the United States is crucial to protect the swine industry from suffering huge economic losses. In August 2016, the Swine Health Information Center (SHIC) funded development of the Rapid Response Program (RRP) to address this need, including recruitment and training of the Rapid Response Corps (RRC) who will respond in the event of an outbreak. This fall, SES, Incorporated will create and implement an exercise to provide refresher training for the RRC on the objectives, procedures, and implementation of the RRP. In addition, an ongoing project keeps the Program and Corps prepared by automating and streamlining the rapid response investigation process via a new web application for the form used by RRC members to conduct outbreak investigations. The web application will be tested in Vietnam, as part of another SHIC funded study to investigate African swine fever (ASF) virus on farms there. The intent is to use the experience in Vietnam to further develop and test the web-based version of the investigation form before it goes live in the United States.
With the development of the online training material and the web-based version of the investigation form, the goal is to offer a standardized approach for outbreak investigations to more veterinarians, epidemiologists, and state and/or federal animal health officials even outside the RRP. This will benefit the swine industry by expanding the pool of individuals with RRP materials available on the SHIC website to conduct their own epidemiological investigations in the face of farm emerging or transboundary disease outbreaks.
And, when needed, the RRC is a team of specifically-trained industry experts to analyze the patterns, causes, and effects of health and disease conditions in affected herds. RRC members, representing six regions of the US, are trained, prepared and committed to moving within 24 hours of contact to conduct epidemiological investigations when a new transboundary or emerging disease threat occurs.
The fall exercise for members of the RRC will offer valuable continuing education, taking into consideration their geographically disparate locations. A series of virtual drills will focus on the key phases of an RRC investigation: pre-investigation, investigation, and post-investigation (reporting). Due to the differences in production facilities and practices for the various phases of hog production, drills will be developed for the primary production phases: sow farms, nurseries, finishers (including wean-finish and gilt replacement) and boar stud operations.
The experience using the web-based version of the investigation form in Vietnam, part of a project being conducted in conjunction with Kansas State University, will provide input on the
content, design, and delivery of the survey. This will help improve the web-based version of the investigation form and provide an opportunity to refine how the data is managed to facilitate analysis of the data and communication of results with all relevant parties. The adaptation of the standardized approach to conducting epidemiological outbreak investigations resulting from this project will allow RRC members to collect a consistent set of information and create a baseline database when using it for endemic diseases, and as a database to be able to efficiently respond in the case of an emerging or transboundary disease outbreak.
The RRC was maintained at 35 members for the duration of this project. To support the continuation of the RRP, and to provide members of the RRC with additional training, a pre-conference seminar was conducted at the American Association of Swine Veterinarian’s Annual Meeting in March 2020. The seminar was titled, “Conducting effective outbreak investigations: Learning from our mistakes, part 2.” The seminar followed the successful pre-conference workshop offered as training for the RRC members at the same meeting in 2019.
Environmental monitoring is commonly used in pharmaceutical, human food, and pet food manufacturing facilities as an indicator of pathogenic bacteria in the product. A correlation between the presence of Salmonella spp. and Enterobacteriaceae (EBAC) within feed mills has been demonstrated, but little information is available on how the presence of EBAC correlates with viral pathogen presence, especially on farms or in feed mills. The purpose of this study, conducted by Kansas State University, was to identify EBAC presence in the feed manufacturing facilities of a multi-farm system experiencing a viral outbreak as a method of identifying biosecurity gaps. Results showed compliance with biosecurity protocols had a substantial impact of EBAC prevalence and distribution throughout the feed mill.
Three separate feed manufacturing facilities were evaluated and sampled for this study, with a biosecurity evaluation and audit performed during each visit. A total of 573 samples were taken over the course of four days, with 381 of those samples consisting of feed ingredient or finished feed, and the remaining 192 samples environmental swabs, collected across the sites. Each swab was assigned one of four zones, including direct feed or ingredient contact surfaces (Zone 1), close proximity non-contact surfaces (Zone 2), non-contact surfaces without close proximity (Zone 3), and transient surfaces, such as moveable tools, employees, and vehicles (Zone 4). Swabs taken from a fourth facility, a multiplier farm, were assigned zones based on proximity to pigs. This included direct feed-contact surfaces (Zone 5), direct pig-contact surfaces (Zone 6) including pen flooring, pen walls, feeders, and waterers (pig contact), and non-pig contact surfaces (Zone 7) including employee walkways, work areas, feed storage, and fans (non-pig contact).
After collection, samples were shipped to the Iowa State University Veterinary Diagnostic Laboratory. Three types of bacteria with largest growth for each sample were identified and reported by assigning a growth index value. Bacterial growth results were assigned an index value of either 0, 1, 2, 3, or 4, based on reported growth, representing no, few, low, moderate, or high growth, respectively.
Maps of EBAC levels per facility are shown in Figures 2, 3, and 4. Audit scores for each facility were Site 1 – 83%, Site 2 – 67%, and Site 3 – 42%. Site 1, 83%, utilized locked exterior doors, required employees to change clothes and shoes prior to entry, and had handwashing stations located inside the doorway. The scale was located within a fenced perimeter and was used to weigh company-owned pigs occasionally. In Site 1, the scale, receiving pit, finished feed bin, and finished feed truck were the only feed-contact surfaces with detected EBAC. At Site 2, 67%, exterior doors were not locked and handwashing stations were not used except for restroom purposes, but employees changed clothes and shoes prior to entry. There was no perimeter fence and the scale was routinely used to weigh animals. There was a moderate quantity of EBAC detected in all feed contact surfaces tested, with high levels on the floor of the manufacturing area. At Site 3, 42%, exterior doors were not locked and handwashing stations not used except for restroom purposes, but employees changed clothes and shoes prior to entry. There was no perimeter fence and the scale was routinely used to weigh company-owned animals, as well as those from other sites within the region. While it was difficult to obtain samples from feed contact surfaces in Site 3, those collected all had high levels of EBAC.
There was significant evidence of a weak correlation (r = 0.201, P ≤0.0001) between EBAC presence and site. There was evidence of moderate correlation noted (r = 0.463, P ≤0.0001) between the zone and presence of EBAC, but no evidence of correlation (r = 0.028, P > 0.05) between zone a presence of fecal indicator bacteria.
Clearly, compliance with biosecurity protocols had a substantial impact of EBAC prevalence and distribution throughout the feed mill. As facilities begin to transition biosecurity from the farm to the feed mill, using environmental monitoring to evaluate risk for biosecurity gaps, as well as success in their mitigation, will be useful and necessary.
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.
This month’s Domestic Swine Disease Monitoring Report shows a similar overall case positivity for porcine reproductive and respiratory syndrome virus (PRRSV), porcine epidemic diarrhea virus (PEDV), and porcine deltacoronavirus (PDCoV) cases in August compared to July. Detection for these agents was within expected parameters for this time of the year. Overall, Mycoplasma hyopneumoniae is following an expected trend of increased detection. At the state level, detection of PRRSV was three standard deviations above expected in Missouri (MO). In the podcast, the SDRS hosts talk with Dr. Derald Holtkamp about strategies to keep disease activity low. They also discuss the economics of disease management and the value of year around biosecurity practices.
Introducing new monthly “Focus on…” feature providing in-depth information and analysis on swine disease issues by geographical region.
This month’s Global Swine Disease Monitoring Report features the launch of new section, “Focus on…” In Part 1 of this new section, read more about swine disease in Asia. The largest outbreak of African swine fever (ASF) of 2020 so far has been reported in Kyiv province of Ukraine. In China, severe measures to control the production and use of illegal ASF vaccines are being taken. And learn more about how the Danish fence on the German border has proved to be effective in reducing wild boars’ density from 35 to 40 to less than 25.