April 2020 SHIC eNewsletter

SHIC and AASV Host Hemorrhagic Tracheitis Webinar – Challenges and Findings to Date

Hemorrhagic tracheitis syndrome (HTS) has been diagnosed in Canada for years and has now reached the US. Practitioners and diagnosticians in Canada and the US provided insight into the syndrome’s progression during a webinar sponsored by the Swine Health Information Center (SHIC) and American Association of Swine Veterinarians (AASV). Held on Thursday, April 2, 2020, the webinar provided information on the syndrome, its signalments, tissues for postmortem assessment, and management. There were 238 participants in the webinar which is available to view here. A timeline of presentations in the webinar is included in this article.

Presenters during the webinar were Dr. Joseph Rudolphi, Rudolphi Veterinary Service Ltd., Dr. Mike Pierdon, Four Star Veterinary Service, Dr. Josepha DeLay, Animal Health Laboratory, University of Guelph, and Dr. Alyona Michael, Iowa State University Veterinary Diagnostic Laboratory.

Dr. Rudolphi shared experience from his practice with HTS, including observations of affected herds, necropsy findings, lab workup information, treatments used, and his theories on how the syndrome affects pigs. Dr. Pierdon relates details from cases of HTS in his clients’ herds, sharing his diagnosis came after the syndrome was no longer affecting animals. He also shares lab workup details, treatments used, and take away messages from the incidents.

Dr. DeLay gave an in-depth look at HTS in Canada from the University of Guelph’s Animal Health Laboratory’s point of view. This includes discussion on etiologies, pathogenesis, and diagnostic challenges. Then Dr. Michael provided an overview from the Iowa State University Veterinary Diagnostic Lab over the past 13 years. This report included timelines, primary pathology identified, culture results, and mechanical factors.

Dr. Michael also shared a diagnostic plan for HTS presented jointly by the Guelph and ISU diagnostic labs for standardization of workups to include case definitions, uniform submissions, and lab evaluations.

Looking for a specific topic or presenter in the webinar? Use the following timeline to go to the segment you choose.

Time Presenter Topic
2:25
Rudolphi
HTS case history
7:06
Necropsy trachea images
10:42
Lab workup
11:21
Treatments
12:19
Theories
17:42
Summary
Time Presenter Topic
19:50
Pierdon
HTS case history
25:15
Lab workup
27:27
Treatment
29:10
Summary
Time Presenter Topic
31:40
DeLay
HTS case history
33:05
Quebec experience
35:00
Guelph lab experience
36:05
Gross lesion images
37:03
Etiologies
37:57
Pathogenesis
43:00
Diagnostic challenges
Time Presenter Topic
47:22
Michael
HTS case history at Iowa State University Veterinary Diagnostic Lab
49:45
Qualifying cases
52:45
Summary
53:41
Proposed diagnostic plan
59:04 Webinar summary / Q & A

SHIC 2020 Webinar Series

SHIC will be offering a series of webinars in 2020, following a successful webinar on porcine sapelovirus and its role in myelitis offered in October 2019. The viral myelitis webinar was recorded and is available on the SHIC website for review. The intent of the webinars in 2020 is to respond to “industry chatter” about current swine health issues. Topics and timing have not been set as the plan is to respond in a timely manner to questions and cases practitioners face, providing resources as well as other veterinarians’ discussion and experience. If you have ideas for webinars, please share those with SHIC Executive Director Dr. Paul Sundberg by emailing psundberg@swinehealth.org.

Farm Crisis Operations Planning Tool

A Farm Crisis Operations Planning Tool for emergency events (e.g. natural disasters, disease outbreaks, public health emergencies or market disruptions) that can lead to reduced or suspended access to resources needed to manage and care for pigs is now available. Development of this resource was a cooperative effort led by Sherrie Webb of the American Association of Swine Veterinarians with National Pork Board, National Pork Producers Council, and Swine Health Information Center staff in response to input received from pork producers concerned about disruptions due to COVID-19. This tool highlights key resources and supplies that may be affected during various states of emergency.

SHIC Study Examines Mitigant Efficacy in Pathogen-Contaminated Feed

The Swine Health Information Center (SHIC) funded a study to evaluate the mitigation potential of chemical feed additives following natural consumption of contaminated and mitigated feed. Prompted by concern over feed biosecurity and other research results suggesting feed can harbor viable viral pathogens and potentially serve as source of infection to susceptible pigs, this study was recently completed and the full report is posted on the SHIC website. Results showed chemical mitigation alone may not be able to completely prevent transmission of pathogens through feed.

It is important to note there are no feed additive products approved as a feed viral mitigant by the FDA. It is illegal to use feed additives in ways and doses other than those on the product’s label. Manufacturers are considering altering their labels for feed mitigation use and FDA has said they will expedite those requests.

The results suggest that chemical mitigation with the tested compounds alone may not be able to prevent transmission of pathogens through feed. Factors that may affect and/or complicate pathogen mitigation in feed include:

Also note, there is likely not one thing that can be done to ensure noncontaminated feed, other than knowing all ingredients were sourced from disease-free areas of the world. Holding time and feed mitigants may help, however, likely won’t sterilize feed.

During the laboratory phase of another project, feed additives were screened against several swine pathogens. Results from that study showed that a select group of feed additives have the potential to be used as chemical mitigants to decrease the risk of pathogen transmission through feed. Limitations of the laboratory study, however, included the fact that: 1) mitigation results were based mostly on laboratory assays; 2) a single, moderate contamination dose was used for each pathogen; 3) the reduction in titers observed after mitigation may not be sufficient to prevent infection/transmission of those pathogens after ingestion of feed.

The moderate amount of contamination used by researchers is common for similar studies. The actual level of contamination coming with feed is unknown. If feed is contaminated, it is likely a spotty or intermittent occurrence. Much research is needed to ensure accurate sampling of bulk feed for viruses. Then, confident manipulation of the samples in the lab will be required for determining virus presence.

Researchers addressed these limitations of the study by performing a feed trial experiment in which animals were allowed to ingest contaminated feed (Senecavirus A (SVA) and porcine epidemic diarrhea virus (PEDV)) or contaminated feed (SVA and PEDV) with a mitigant (A, B, and C) for three consecutive days. For this animal trial, the top three candidate mitigants, A (a medium chain fatty acid), B (a blend of organic acids and methionine hydroxy analogue (HMTBa)), and C (a blend of medium chain fatty acids), from the previous laboratory mitigation project were selected. After feeding, each animal was sampled individually and levels of viremia, virus shedding, and viral load in tissues were determined by RT-qPCR. Importantly, animals in each treatment group were fed mitigated feed during the entire experimental period (14 days).

Results showed that under the conditions used in the animal clinical trial, in which every animal in the study ingested contaminated feed via natural feeding the efficacy of the mitigants was low. Out of the three mitigants tested, only mitigant A reduced SVA infection when a low contamination dose of the virus was used, as evidenced by lower levels of virus shedding and viral load in tonsil of exposed animals.  When the contamination levels were increased to moderate, no significant differences were observed between the mitigated and non-mitigated treatment groups, with all animals presenting similar levels of virus shedding and viral load in tonsil.

Consequently, if or when these compounds gain FDA approval for feed viral mitigation, adding them onto alternative strategies such as storage time and importation of feed ingredients from known and trusted sources should be considered to safeguard the US swine industry from unwanted viral pathogens. Additionally, studies on the mechanism of action of potential mitigants may also allow selection of those compounds that present the greatest chance of virus inactivation in the feed matrix or that modulate the pig immune responses, thus reducing the risk of potential pathogen transmission through feed.

April Swine Disease Monitoring Reports

Domestic Disease Monitoring Report

In the April report, we learn porcine reproductive and respiratory syndrome (PRRS) virus cases were up in March over February with detection on sow farms the highest level since March 2013. This was unsurprising due to favorable climate for virus spread during March. Porcine epidemic diarrhea virus (PEDV) cases were down in March over February in all age categories. Porcine delta coronavirus (PDCoV) cases were up slightly in March over February following expected seasonality. Mycoplasma pneumonia (MHP) cases were down in March as well, also following expectations.

Global Swine Disease Monitoring Report

The Global Swine Disease Monitoring Report for April includes information on experimental results from the Friedrich Loeffler-Institut (FLI) showing pigs are not susceptible to the virus responsible for COVID-19. In the report summary, FLI reported pigs and chickens could not be productively infected by SARS-CoV-2 under the experimental conditions used in their work. The study also shows virus replication in ferrets resembles the situation of a mild human infection. Read the entire report summary here. In Poland, the first two outbreaks of African swine fever (ASF) in commercial pig farms in the western part of the country are reported as well as notes that ASF detected in wild boar 10 km from the German border. Papua New Guinea authorities confirmed the first ASF outbreak in Southern Highlands province which has the Australian swine industry on high alert. ASF is suspected in Bali. And a report review on Business Continuity in the Face of African swine fever – Compartmentalization Strategy is also included.