Pathogen Transmission White Paper
May 9, 2017
The Marketing Journey of Cull Sows and Secondary Market Pigs
June 21, 2017

Diagnostic Support Fuels Search for Answers

Sometimes, the cause of herd health problems is not easily identified. When initial diagnostic work paid for by the producer is inconclusive yet the health issues remain unidentified, and there are incidents of high or ongoing morbidity or mortality where a known pathogen is not the likely cause of the outbreak, SHIC offers diagnostic fee support for further study to help identify newly introduced or emerging swine diseases.

In one case, SHIC diagnostic fee support identified porcine sapelovirus in an acute outbreak of atypical neurologic disease. Prior to this finding, sapelovirus from other species have not been reported to be associated with nervous system disease. Here, a novel sapelovirus was the only agent detected associated with a unique clinical presentation of central nervous system (CNS) disease.

In another instance, SHIC provided diagnostic fee support for a case of increased death loss associated with acute onset of CNS signs, initially described as tremors, in a grow-finish herd. An abundance of pasivirus was detected via molecular techniques but was not definitive evidence for disease causation. SHIC is continuing to monitor for diagnostic trends that might help better determine if pasivirus is implicated as an emerging disease issue.

A description of the requirements, submission and review process for the Support for Diagnostic Fees program can be found on the SHIC website by clicking here. The Swine Health Information Center (SHIC) Swine Disease Matrix contains the pathogens posing the greatest threat to the US swine herd. If any of the symptoms of these viruses appear in a US herd, diagnosis needs to be swift.

 

Pathogen Transmission Via Feed May Be Possible

In preliminary findings, a study conducted by Pipestone Applied Research and South Dakota State University shows the potential for PRRSV and other viruses to contaminate and survive in feed ingredients, including soybean meal (SBM) and dried distillers grains (DDGs). The study is based on a model simulating the transboundary movement of contaminated ingredients that was developed to identify “high risk combinations” of viruses and feed ingredients. Read the entire white paper here.

The Swine Health Information Center (SHIC) is interested in discovering potential risks to the US pork industry and has provided significant funding for this ongoing work. The SHIC Swine Disease Matrix was used to identify target viral pathogens for evaluation in the study. Researchers used “surrogate viruses” in some instances which allowed study of closely related and structurally similar viruses.

This research examined multiple viruses for their ability to survive under shipping conditions coming into the US. Preliminary data indicate the survival of viruses and surrogate viruses including the Seneca Virus A (surrogate for FMDV and of interest itself), Bovine Herpesvirus-1 (surrogate for Pseudo-rabies virus), and PRRSV (using PRRSV 174) during the 37-day study period. Ingredients frequently supporting virus survival include SBM, lysine, choline, and Vitamin D, and, in some cases, DDGs. Other products were not shown to consistently support viral survival during the 37-day study period. In the process, a subset of viruses has also been recovered from pork casings and different kinds of pet food. None of the viruses survived the 37-day incubation period in the absence of a feed component matrix.

The 37-day incubation period is chosen because it is the amount of time it would take ingredients to be transported from Bejing, China, to Des Moines, Iowa, and consequently represents the prospective window for disease transmission.

These results suggest a subset of contaminated feed ingredients could serve as vehicles for foreign animal disease, other transboundary introduction in the US, and possibly circulation of viruses within the US. In particular, the PRRSV data may provide new insights and areas of further study on the role of area spread.

Further mitigation research has already begun. This process will include testing of a variety of feed additives that might be able to neutralize these pathogens when added to feed during milling or other processes that may help mitigate risk.

Heat treatment during corn processing into DDGs and soybean conversion into SBM should neutralize pathogens present on the corn kernel or bean prior to processing. However, research at Kansas State University has shown the potential for porcine epidemic diarrhea virus (PEDV) contamination of feed during the milling process if PEDV is present within the feed mill emphasizing the need for feed mill biosecurity plans. Although, more information is needed about oral viral infective doses to accurately assess risk.

 

Central Nervous System Cases Prompt Concern

The Swine Health Information Center (SHIC) has been monitoring unusual central nervous system (CNS) cases detected over the last six months in the US. Clinical signs have included ataxia, muscle tremors, and muscle weakness possibly leading to paralysis. In 12 of 17 cases reviewed, sapelovirus and/or teschovirus have been detected. Veterinary diagnostic laboratories have issued the diagnoses.

  • Average pig age – 10 weeks
  • Morbidity from 10 to 15 percent
  • Mortality – 100 percent

To date, a wide array of antibiotics and vitamins has not had any apparent benefit and no out of water events were detected.

Producers and practitioners are encouraged to watch for unresolved neurologic cases and submit samples to their veterinary diagnostic lab for diagnosis. CNS clinical signs reflecting functional compromise of brain stem, spinal cord, and cerebellum or cerebrum that make up the case definition and initiate voluntary reporting include ataxia, muscle tremors, and muscle weakness.

SHIC has established guidelines to help identify and report CNS cases. Access those guidelines here.

 

SHIC Monitoring New Incidence of Classical Swine Fever Virus Circulating in China

Reports from China say a new subgenotype of Classical Swine Fever virus (CSFV) is responsible for recent outbreaks. Further results show specific antibodies elicited by vaccination of C-strain vaccine could not effectively protect against the new strains of CSF found in China, leading to the new cases.

An article in the Veterinary Microbiology journal (201, 2017, 154-161) highlights an emerging disease issue occurring in China. For decades, CSF has been controlled in China due to extensive, mandatory vaccination with C-strain-based commercial vaccines. Recent frequent CSF outbreaks in this Asian nation have raised concern internationally and the Swine Health Information Center (SHIC) is monitoring developments closely.

These discoveries are setting the stage for additional study using field situations to evaluate both the virus strains and vaccines to combat outbreaks. Read the entire paper on this subject from the Veterinary Microbiology journal here.

SHIC remains engaged in global monitoring of swine pathogens and committed to relaying information on threats to the global herd.

 

Industry Organizations Lead Planning for a National Bio-surveillance System for US Swine Industry

In April, the Swine Health Information Center (SHIC) joined the Institute for Infectious Animal Diseases (IIAD), a Department of Homeland Security (DHS) Center of Excellence, and the National Pork Board (NPB) to host a workshop to discuss and build upon industry and government efforts identifying and developing a road map to address gaps for a nationally coordinated bio-surveillance system. In addition to the hosts, participants included pork producers, swine veterinarians, American Association of Swine Veterinarians, National Pork Producers Council, as well as state and federal animal health officials. The workshop also received sponsorship from the DHS Science and Technology Directorate.

Workshop Objectives

  • Identify gaps, tools, and research needs for a workable, credible, affordable, and robust national bio-surveillance system supporting coordinated early detection, rapid response and efficient control of foreign animal diseases (FADs), and enables improved prevention of FADs and emerging/re-emerging priority diseases to the US swine industry
  • Develop a road map to address gaps, barriers, and research needs (identified in Objective 1) for improvement and implementation of the sustainable successfully functioning, national, rapid bio-surveillance system meeting the needs of the US swine industry as well as state and federal animal health authorities.

There was a significant consensus among industry stakeholders participating in the workshop regarding the attributes of an optimal risk based comprehensive disease preparedness system and belief a modern robust national bio-surveillance system is a vital component. Find the attributes and the priority action items the group developed here. Among all participants there was a commitment to timely forward progress.

The United States Department of Agriculture, Animal and Plant Health Inspection Service (USDA APHIS) currently has regulatory surveillance programs (pseudo rabies, brucellosis and classical swine fever), monitors for influenza and vesicular diseases and is in the process of evaluating the parameters to develop a comprehensive US swine surveillance program. Additionally, the US swine industry actively monitors for swine diseases in a continual effort to protect the health and welfare of the country’s swine herd.

Swine health and food safety is of paramount importance ­– the industry has more than 60,000 pork producers who annually market more than 110 million hogs, equaling total gross receipts of $23.4 billion, supports 550,000 jobs, and contributes $39 billion to the U.S. Gross Domestic Product. With record industry expansion in recent years, pork production exports have risen to more than 26 percent of US production – a number that is expected to continue to increase. With an ever-expanding industry, diseases that can disrupt trade and commerce are of increasing concern, making adapting the nation’s current surveillance system to keep up with the industry’s needs and speed of commerce of upmost importance.