SHIC, launched in 2015 with Pork Checkoff funding, 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 http://www.swinehealth.org or contact Dr. Sundberg at [email protected].
Introducing important work examining the role of contaminated feed as a vector for transmission of foot-and-mouth disease virus (FMDV), a new study, funded by SHIC, the National Pork Board and ARS/USDA, was published in July 2021.* Specifically, the study performed by researchers from ARS/USDA at Plum Island, evaluated the potential risk of incursion of FMDV into naïve pig herds through contamination of feed. Per the study report, the goal of the project was the assessment of the infectiousness (viability) of FMDV in commercial whole pig feed and pig feed ingredients. Additionally, the researchers, led by Drs. Stenfeldt and Arzt, determined the dose required to infect pigs through natural feeding behavior. Finally, the project looked at the ability of select commercially available feed additives to reduce infectivity of contaminated feed. “While comparable research investigating the potential biosecurity risks of imported feed exists for other viral pig pathogens (Dee et al., 2018; Niederwerder et al., 2020; Niederwerder et al., 2019), this is the first comprehensive evaluation of the risk of FMDV infection of pigs through ingestion of contaminated feed under controlled experimental conditions,” wrote the authors.
In discussion of the study, authors noted many conditions must be met for transmission of viral diseases through pig feed to occur. They also acknowledged that understanding these conditions is critical in order to quantitate the associated risk as well as consider preventative measures. Per their report:
In this study, these requirements were considered in the context of pathogen incursion occurring before or during transoceanic transport (Dee et al., 2018). The combined output from the current investigation demonstrated that the likelihood of all of these conditions being met will depend on:
In the conclusion, authors wrote, “The combined output of this investigation demonstrated that FMDV can remain viable as a contaminant of pig feed products through 37 days. In addition to expected variation associated with storage temperature, there was also substantial variability in viability of different FMDV strains in different feed matrices. FMDV exposure by feeding of experimentally contaminated feed to pigs caused FMD with dose dependency. The minimum dose required to cause FMD varied between virus strains and with experimental design and the probability of infection increased when a given dose of virus was divided across three consecutive feedings, likely due to increased exposure time.”
Findings of this work demonstrate:
* Stenfeldt, C., Bertram,M. R., Meek, H. C.,Hartwig, E. J., Smoliga, G. R., Niederwerder,M. C., Diel, D. G., Dee, S. A., & Arzt, J. (2021). The risk and mitigation of foot-and-mouth disease virus infection of pigs through consumption of contaminated feed. Transboundary and
Emerging Diseases, 1–16. https://doi.org/10.1111/tbed.14230
Following the discovery of African swine fever (ASF) in the Dominican Republic, the U.S. Department of Agriculture’s Animal and Plant Health Inspection Service invites participation in daily webinars, September 13-17, 2021, to learn more about the virus and its global spread. The webinars will also cover actions APHIS is taking to safeguard the US and biosecurity measures producers can implement now to protect the US herd. To register, click on the webinar title below.
Monday, September 13
ASF: Where it Exists and What’s at Stake
2:00 to 3:30 p.m. EDT
Tuesday, September 14
Steps APHIS is Taking to Prevent and Prepare for ASF
2:00 to 3:30 p.m. EDT
Wednesday, September 15
ASF and the Benefits of Biosecurity
2:00 to 3:30 p.m. EDT
Thursday, September 16
What to Expect in an ASF Outbreak
2:00 to 3:30 p.m. EDT
Friday, September 17
ASF and the Feral Swine Factor
2:00 to 3:30 p.m. EDT
A dead pig was submitted to the South Dakota State University Animal Disease Research and Diagnostic Laboratory (SDSU-ADRDL) in October 2020 for diagnostic testing. Moderate enteritis, hepatitis, and visceral edema along with hemolytic E. Coli were discovered as well as porcine circovirus type 2 (PCV2). Later, viral metagenomic sequencing was performed on archived lung tissue for an unrelated research project. Unexpectedly, canine parvovirus 2 (CPV2) was also identified. This finding led SDSU-ADRDL staff to ask for support from the Swine Health Information Center (SHIC) to study spillover of the virus from the canine species to swine; the investigation has begun. The specific goal of this project is to investigate the epidemiology of CPV2 in pigs and evaluate its pathogenesis in a colostrum deprived pig model.
Besides CPV2, which causes enteritis in dogs and myocarditis in puppies, the species includes feline panleukopenia virus (FPV), which causes severe enteritis and leukopenia in cats of all ages. CPV caused a worldwide pandemic in 1978 following a spillover event from FPV. Continued host switching with CPV has been documented, with spillover to wildlife including skunks, raccoons, and coyotes resulting in both clinical disease and asymptomatic infection. Determining the potential consequences for spillover from canines to swine will inform both diagnostic and prevention efforts for pork producers.
Results of the study at SDSU-ADRDL are expected in six months and will be shared by SHIC as part of its mission to protect the health of the US swine herd from emerging disease threats.
Research being conducted in Vietnam on ELISAs for African swine fever (ASF), made possible by a USDA Foreign Agricultural Service grant obtained by the Swine Health Information Center (SHIC) with support from the National Pork Producers Council, continues with a preliminary report issued in July 2021. This work is being done by Biostone Animal Health, with collaboration with the Canadian Food Inspection Agency’s (CFIA’s) National Centre for Foreign Animal Disease (NCFAD). Goals of the study are to generate a panel of 2000 pig serum samples with known ASF infection status, determine the diagnostic sensitivity and specificity of the ELISAs in the study using the panel, and finally to perform an inter-laboratory evaluation of the assays in the USA and Canada.
To date, CFIA-NCFAD has received 790 ASF pig serum samples from Vietnam. In addition, Biostone Animal Health has received 500 ASF negative pig serum samples from Iowa State University, the University of Minnesota, and South Dakota State University. NCFAD has 500 ASF negative samples also available.
Preliminary results using the ELISA assays in the study shows high test sensitivity and specificity (>98%). Using preliminary results, further improvements have been made to the ELISAs.
Next steps in evaluating sensitivity of the assays include testing additional samples collected from pigs infected with multiple ASF strains including those that cause less severe clinical signs. Biostone Animal Health is also looking for collaborators in other ASF endemic countries to further validate the assays.
On August 4, 2021, USDA’s Animal and Plant Health Inspection Service (APHIS) issued a Federal Order establishing additional requirements for dogs imported into the US for resale from countries where African swine fever (ASF) exists. The new requirements took effect immediately. Per the USDA, the number of dogs being imported for resale from ASF-affected countries is growing, and APHIS took this action to continue its efforts to protect the domestic swine industry against this devastating disease.
This USDA APHIS effort was lauded by US swine industry organizations that raised the issue and worked cooperatively to encourage the tightened regulations. “Each year, several thousand dogs enter the country for resale or adoption,” National Pork Producers Council (NPPC) Chief Veterinarian Liz Wagstrom said. “If even one of these animals carried ASF into the country, it could put the US swine herd and other livestock in jeopardy and have disastrous consequences for our nation’s agriculture sector.”
Credit goes to the swine industry organizations for their response to the issue of dog imports from ASF-affected countries, first noted in mid-2019 and again in early 2021. “The swine industry raised this issue and provided the necessary data and support to encourage a regulatory change. There was no recognition at either the federal or state level that this was going on or the frequency with which it occurred. There was no tracking of these dogs, veterinary evaluation, quarantine, follow up, or effective monitoring due to lack of livestock health related regulation,” commented Harry Snelson, DVM, executive director of the American Association of Swine Veterinarians (AASV).
The Swine Health Information Center (SHIC) joined NPPC, AASV, and the National Pork Board (NPB) to increase awareness with USDA officials. “This outcome is a great example of the pork associations identifying a foreign animal disease entry risk and the state-federal-industry cooperation that had to happen to close a possible FAD pathway of entry into the US. The whole US pork industry is grateful for this final, decisive step,” stated SHIC Executive Director Paul Sundberg, DVM, PhD, DACVPM. The American Veterinary Medical Association (AVMA) also joined in the effort to encourage USDA rule changes.
“The issue of importation of dogs from ASF countries highlighted a gap in biosecurity. To identify the issue and then take action to address that gap was important to strengthen protection against ASF and other foreign animal diseases,” said Lisa Becton, DVM, director of swine health at NPB. “Having industry highlight this risk was important because it helped to address gaps in the methods used to track these imported dogs. The industry groups helped to home in on this risk and to focus actions to directly address this risk.”
The swine industry recognizes the delicate balance this situation demands given some imported dogs are being rescued from the meat trade in China. However, the process presented a great risk to animal agriculture that needed to be addressed. “This was a legal activity that allowed the uncontrolled introduction of animals and materials derived directly from some high-risk countries and high-risk venues within those countries (such as wet markets) into the US where the further distribution of the animals was unmonitored and unrecorded and the management of potentially contaminated materials was unregulated,” Dr. Snelson observed.
While Dr. Wagstrom said the potential for dogs to introduce ASF into the US swine herd a low likelihood, she noted the catastrophic consequences. “The probability of an imported dog carrying swine blood or manure contaminated with AFS to a US farm – or contaminated bedding from international transport finding its way to landfill where wild pigs could be exposed – might not be high, the impact would be devastating,” she explained. “We would lose all of our export markets, leading to tremendous losses across the pork industry.”
In its announcement, USDA stated said it continues to work with a wide range of partners, including the swine industry, producers, other government agencies, and neighboring countries to keep ASF out of North America. Drs. Becton, Snelson, Sundberg, and Wagstrom all expressed thanks to the USDA for their response to the issue. “This effort highlights the important close working relationship between the swine industry and our federal and state partners to identify and address these risk areas,” Dr. Becton said.
An updated fact sheet on porcine circovirus 3 (PCV3) has been posted on the Swine Health Information Center (SHIC) website containing the latest information available. PCV3 is a newly detected pathogen of swine. Although most cases have been detected subclinically, PCV3 is also associated with clinical signs similar to those caused by porcine circovirus 2 (PCV2). Individual case definitions have been proposed for PCV3-associated reproductive disease and systemic disease to standardize diagnostic criteria. Work continues at veterinary diagnostic labs (VDLs) where a case definition is being developed. The VDLs are collecting clinical signalment from practitioners who have a PCV3 diagnosis in clients’ herds and are combining it with diagnostic test result qualifications. When this work is finished, communicated in the industry, and generally accepted, SHIC will then move on research priorities and needs. Research will further characterize the clinical and economic outcomes of a PCV3 diagnosis. Case definition completion and beginning of research are expected yet in 2021. Fact sheet updates are part of SHIC’s mission to protect the health of the US swine herd, providing guidance and resources for producers, practitioners, and diagnosticians who are on the front lines of swine health concerns is paramount.
PCV 3 has been associated with reproductive failure, porcine dermatitis and nephropathy syndrome (PDNS), and multi-systemic inflammation. However, only a few studies have demonstrated the presence of PCV3 in lesions. Anecdotally, PCV3 has been detected in neurological, respiratory, and enteric cases, but causation has not been established. In pathogenicity studies, PCV3 inoculation does not consistently lead to development of clinical disease. Individual diagnostic criteria proposed for PCV-3-reproductive disease (PCV-3-RD) include late reproductive problems and higher perinatal mortality, multi-systemic lymphoplasmacytic to lymphohistiocytic perivascular inflammation, and moderate to high amount of PCV-3 genome in damaged tissues. Individual diagnostic criteria proposed for PCV-3-systemic disease (PCV-3-SD) include weight loss, rough hair, neurological signs, multi-systemic lymphoplasmacytic to lymphohistiocytic perivascular inflammation, and moderate to high amount of PCV-3 genome in damaged tissues
PCV3 is found in wild and domestic pigs. Antibodies to PCV3 have been detected in dogs, cattle, and mice. PCV3-positive mosquitoes have been found. Wild ruminants and ticks may also be reservoirs. PCV3 is found in many swine-producing regions of the world. Epidemiological studies have found that infection is widespread, with prevalence up to 100%. Little is known about the course of natural infection. A few studies have shown that prevalence is highest in piglets/weaners and decreases with age, but PCV3 has been detected in pigs up to 23 weeks-of-age.
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 that a moderate decrease on the overall porcine reproductive and respiratory syndrome virus (PRRSV) and the PRRSV RFLP 1-4-4 L1C variant strain was observed. Even though a lowering in the detection of enteric coronavirus occurred, similar to July detection for porcine epidemic diarrhea virus (PEDV) in the age category wean-to-market was observed in August. A moderate increase in the detection of M. hyopneumoniae by PCR and signals on the disease diagnosis monitoring were identified. In the podcast, the SDRS hosts talk with Dr. John Deen, University of Minnesota, about his experience on animal health management, control, and how to intervene to improve sows’ longevity. The bonus page provided by Dr. Holtkamp, Iowa State University, brings international benchmarking of key performance indicators in pork production.
In the September Global Swine Disease Monitoring Report, it is said Dominican Republic authorities have confirmed the detection of African swine fever (ASF) outbreaks in at least 18 provinces. More than 31,000 animals have been destroyed so far to control the spread of the disease on the island nation. A Protection Zone in Puerto Rico and the U.S. Virgin Islands is being sought by USDA-APHIS. This World Health Organization (OIE) recognition would protect pork export continuity for product from the mainland US. In El Paso, Texas, over 300 pounds of smuggled pork have been confiscated by Customs and Border Protection agents.