Science Page: An overview of African Swine Fever

This is our Friday rubric: every week a new Science Page from the Bob Morrison’s Swine Health Monitoring Project. The previous editions of the science page are available on our website.

This week, we are sharing a fact sheet regarding African Swine Fever, followed by a map of the current outbreak situation.

Keypoints

  • Recent outbreak of African swine fever in china may have influence in the global trade market of pork during the following months.
  • Prevention focusing on imports and international movements is the best strategy in absence of a vaccine.
  • Rapid diagnostics and culling are key components of an effective eradication.

After the recent outbreak of African swine fever in China and the implications for international trade, swine health, and production we thought it would be a good idea to review the characteristics of the disease.

INTRODUCTION

African swine fever (ASF) ranks third as a potential risk that could threaten the US swine industry in the swine disease matrix, from the Swine Health Information Center (SHIC). ASF is a highly contagious disease that causes hemorrhages in pigs. It is caused by a DNA virus from the Asfaviridae family. It affects pigs, warthogs, and European and American wild boars.

CLINICAL SIGNS

Clinical signs vary depending on the virulence of the virus. Severe infections can cause up to 100% mortality in 2Ͳ7 days with high fever as the main characteristic. Other relevant clinical signs are bleeding (nose or rectum), diarrhea, redness of ear, abdomen, or leg skin, respiratory disorder, loss of appetite and depression. Moderately virulent strains cause less intense symptoms as the beforehand mentioned but mortality can still range between 30-70%. ASF can also be found in a chronic form with loss of weight, discontinuous fever, respiratory signs, skin ulcers and arthritis.

DIAGNOSTICS

Appearance of clinical signs and high mortality rates may trigger suspicion of ASF but confirmation has to be done through laboratory test. Differential diagnosis includes classical swine fever (CSF), high pathogenic porcine reproductive and respiratory syndrome (HPͲPRRS), swine erysipelas, septicemic salmonellosis and porcine dermatitis nephropathy syndrome (PDNS).
Diagnostic techniques include detection of antibodies in serum or the etiologic agent in different tissues (blood, spleen, lymph nodes, tonsil and kidney). Isolation, PCR,Haemadsorption test and Antigen detection by fluorescent antibody test are the techniques for the virus identification.

EPIDEMIOLOGY

The warthog is the main reservoir of the disease and it transmits form pig to pig through a soft tick. Wild boars and other wild pigs can also carry and spread the disease. Domestic pigs usually become infected through direct contact with sick pigs or eating pig meat containing ASF virus. Also indirect spread can occur through contaminated vehicles, premises, equipment or clothes.

PREVENTION AND CONTROL

No treatment or vaccines are available at this point. Therefore the best strategies are implement strategies to avoid the introduction of the virus is to focus on import policies and movement of vehicles and people from infected countries. Rapid diagnosis and culling are the key features of a successful eradication program along with surveillance, movement controls, cleaning, and disinfection of the affected premises.

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Map of the current ASF outbreaks. Source: OIE

CURRENT SITUATION

Since the disease landed in Georgia in 2007 ASF has made steady progress through Europe.Latvia, Lithuania, Poland and more recently Hungary are the last countries that reported the presence of the disease in Europe. The outbreak occurred in one of the most swine dense regions China, relatively close to the Korean peninsula. Three other cases have been reported to date. The effects of the outbreak will probably shape the global
trade of pork in the following months.

 

Best of Leman 2017 series #9: P. Davies – Emerging Issues in Antibiotic Resistance Linked to Use in Food Animals

We launched a new series on the blog in October. Once a month, we are sharing with you a presentation given at the 2017 Allen D. Leman swine conference, on topics that the swine group found interesting, innovative or that lead to great discussions.

Our 9th presentation is by Dr. Peter Davies regarding Emerging Issues in Antibiotic Resistance Linked to Use in Food Animals.

The 2018 Leman Swine Conference is in a few weeks, register now!

To listen to this talk, please click on the image below.

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What is new for the 2018 Leman Swine Conference?

Registration for the 2018 Allen D. Leman Swine Conference is open!

We are looking forward to welcoming you in the beautiful St. Paul, right by the Mississippi river for another exceptional science-driven program. We keep innovating to bring you even more quality content and we are proud to present these new initiatives.

Honoring Dr. Bob Morrison

Morrison Lecture

For the first time, the Morrison lecture will become a prominent feature of the Leman Program. This keynote lecture in honor of Dr. Morrison is given to individuals that do work that matters to the swine industry. The inaugural Morrison Lecture will be presented by Dr. Brad Freking of New Fashion Pork, and a graduate of our DVM program.

Morrison Swine Innovator Prize

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We also wanted to recognize Bob’s dedication to DVM education and innovation. For the second year, swine focused DVM students from across the country have been invited to presenting on Sunday afternoon on practice-ready tips and problem solving skills. This year, the presentations will be formally judged and the student giving the most outstanding presentation will be awarded the Morrison Swine Innovator Prize.

Morrison Fellowship

A further part of the Morrison Legacy Fund initiative is the Morrison Fellowship. This fellowship will be awarded annually to a graduate student who is dedicated to research in swine health and production. Dr. Alyssa Betlach is the first recipient of the Morrison fellowship, and we look forward to her contributions in the area of Mycoplasma control to improve herd productivity.

Keynotes lectures

Pijoan Lecture

This year Pijoan Lecture will be given by Dr. Mike Murtaugh in the topic of PRRS after 30 years of having affected the swine industry and how such devastating disease has become a model for advancing progress in the swine industry.

The Pijoan Lecture is named in honor of Dr. Carlos Pijoan for his work in the area of swine respiratory disease and the influence of swine production systems on the dynamics of microorganisms such as porcine reproductive and respiratory syndrome virus, Haemophilus parasuis, Streptococcus suis, and Mycoplasma hyopneumoniae.

Distinguished Lecture

This year Distinguished Lecture will be given by Alida Sorenson and Dr. Scott Dee and will cover the important topic of food and feed transboundary biosecurity.

Science in Practice

The 2018 Leman Science in Practice Award recipient is Dr. Rebecca Robbins. Dr. Rebecca Robbins is the senior production veterinarian for Seaboard Foods.  Based in Guymon, Okla., she and her veterinary team are responsible for the health and well-being of 280,000 Seaboard Foods sows farrow-to-finish located in Colorado, Kansas, Oklahoma and Texas. Rebecca serves on Seaboard Foods’ research and development team, which coordinates an average of 45 studies per year.

Dr. Robbins is chairing a session on the problems and solutions for integrated pork production on Monday afternoon. Experts will share their perspectives on what it means to be a veterinarians in a system and how to approach feeding and disease challenges.

Beer and Bacon Conversations

sizzling-2650322_1920We are excited to try a new format for our Conversation Series. Instead of trying to coax people out of bed first thing Monday morning, we now will tempt you to join in a Beer and Bacon Conversation session on Sunday afternoon. Our first conversation in the new format will be with Dr. Mathew Turner who will discuss with Dr. Marie Culhane his views on pigs, the industry, and life as a swine veterinarian. Who can resist beer and bacon?

You don’t want to miss it! Register today!

African Swine Fever in China: a Swine Disease Global Surveillance Report

This report was published from the Swine Health Information Center and prepared by the University of Minnesota.

Thursday, August 16, 2018

There is now a second case of African swine fever (ASF) in China.  It was found in a slaughterhouse where 30 pigs died of ASF. The slaughterhouse is located in the city of Zhengzhou in the Henan province. The pigs came from Tangyuan district of the city of Jiamusi, in the Heilongjiang province, over 500 miles to northeast of the first reported herd, which was detected approximately two weeks ago.

By road, the distance from the farm to the slaughterhouse is approximately 1,400 miles, travelling through areas with high pig density. The slaughterhouse is a large commercial facility, owned by Shuanghui, part of the WH Group, the world’s largest pork producer.

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Government officials are moving quickly to try to isolate the disease. The slaughterhouse has been closed with a no movement zone within a radius of approximately of 6 miles and a zone of 2 miles for destroying all pigs.

This news outbreak signals that there may be a number of concerns about the status of ASF in China.  The distance between the original detection in Shenyang and this newly identified farm, as well as slaughterhouse, shows that the disease is being transported widely. The areas of concern now involve multiple Chinese provinces and heighten the likelihood of further cases.

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4 key locations: Red dot, new ASF outbreak reported in slaughterhouse is located in the city of Zhengzhou in the Henan province; blue: first ASF outbreak reported in a small pig farm in district of Shenbei New, in the province of Liaoning; green dot: farm (owner Wang) located in the Hunnan District, Shenyang city, Liaoning province; purple: Tangyuan district of the city of Jiamusi, in the Heilongjiang province.

The Chinese press is reporting that the outbreak started as early as April of this year.  (http://www.chinanews.com/sh/2018/08-15/8600530.shtml) A partial translation is below.

The first ASF case was officially confirmed on Aug 3, 2018 on a small farm (owner Zhang) located in the Shenbei District, Shenyang city, Liaoning province.  Further investigations indicated that the owner of the ASF index farm purchased 45 pigs on July 5, 2018 from a farm (owner Wang) located in the Hunnan District, Shenyang city, Liaoning province. Fecal samples collected from Wang’s farm were confirmed ASFV RNA positive by PCR.

Wang said that the last entry of pigs onto the farm occurred on March 24, 2018. There were 100 piglets purchased from Chuanying District, Jilin city, Jilin province.  In April, some pigs started to become sick and then died on the Wang farm. Wang did not report the abnormal pig death; instead the remaining live pigs were sold to the Zhang farm in Shenyang and other people. So far, all of the pigs initially from the Wang farm have been tracked and culled.  Wang was held in a detention center due to violation of the laws.

Science Page: An Overview of Porcine Astrovirus

This is our Friday rubric: every week a new Science Page from the Bob Morrison’s Swine Health Monitoring Project. The previous editions of the science page are available on our website.

This week, we are sharing a disease sheet on porcine astrovirus by Drs. Arruda and Schwartz.

Key points:

  • Further research is needed in all areas of the virus in order to better understand, treat, and prevent Astrovirus.
  • Astrovirus is a public health concern in humans as it is implicated in foodborne illnesses and has zoonotic potential.
  • Porcine Astrovirus may play a role in enteric disease, and has been associated with neurological disease.

Porcine Astrovirus (PoAstV)  is a nonenveloped RNA virus with 5 different strains present in U.S herds. It has been detected in both healthy and diseased pigs, so more research is needed to determine the clinical implications of a PoAstV infection. Recently a U.S swine production system reported PoAstV-associated neurological disease. In the sow farm 100% of pigs affected with disease died, while in the growing-finishing farms case-mortality rate was 75%. Signs exhibited by affected animals included paralysis, ataxia, paresis, and knuckling, which eventually progressed into lateral recumbency.

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Scientific publications relating to Porcine Astrovirus are rare. The majority of information, however, supports fecal-oral as the main route of transmission. Some reports have shown PoAstV to retain infectivity in ground water for extended periods of time and can survive up to 3 hours in water with a p.H of 4.0. There is currently no vaccine available for this disease. The large antigenic diversity and high mutation rate are the biggest challenge for vaccine development. Diagnosis is typically made via PCR.

The major concern with Astrovirus is the zoonotic potential. Human Astrovirus is easily transmitted through contaminated food and water and causes moderate gastroenteritis in infants. Human-to-pig transmission is suspected due to the detection of human-porcine recombinant viruses. Pig-to-human zoonosis has not been reported, but Astroviruses can rapidly mutate, so it may be only a matter of time before a zoonotic strain emerges.

Further research into pathogenesis and vaccine development is crucial to prepare for a possible zoonotic outbreak. 

— Blog post written by Joseph Thurston.

Pioneering Structural Study of Porcine Coronavirus

Today, we are highlighting the research of a completely different team at the University of Minnesota. The Minnesota Supercomputing Institute provides advanced research computing infrastructure and expertise to advance and accelerate research and foster innovation and discoveries.

MSI PIs Wei Zhang (research associate professor, Diagnostic and Biological Sciences) and Fang Li (associate professor, Veterinary and Biomedical Sciences) have published a new paper that describes some of their continuing research into the structure of coronaviruses. These are a large group of viruses that includes such deadly diseases as SARS and MERS. Coronaviruses have four forms, known as α-, β-, γ-, and δ-coronavirus, which affect different hosts. For example, β-coronaviruses affect only mammals, while the δ form affects both birds and mammals.

The coronavirus structure includes a feature called a “spike protein,” which allows the virus to attach to the host’s cells. The spike proteins of α- and β-coronavirus have been well studied. The spike protein of the δ-coronavirus, however, is described for the first time in this paper. The researchers used cryo-electron microscopy, a fast-developing technology in which protein molecules are studied under ultra-cold temperatures with an electron microscope. This technology was used to determine the structure of the spike protein of porcine δ-coronavirus (PdCoV), a lethal virus infecting pigs, elucidating how PdCoV infects pigs cells and evades the host immune system. This is the first atomic-resolution cryo-electron microscopic study from the state of Minnesota, and is a milestone in the structural biology field at the University of Minnesota.

Zhang Li spike protein porcine deltacoronavirus

Image Description: Overall structure of PdCoV S-e in the prefusion conformation. (A) Schematic drawing of PdCoV S-e (spike ectodomain). S1, receptor-binding subunit. S2, membrane fusion subunit. GCN4-His6, GCN4 trimerization tag followed by His6 tag. S1-NTD, N-terminal domain of S1. S1-CTD, C-terminal domain of S1. CH-N and CH-C, central helices N and C. FP, fusion peptide. HR-N and HR-C, heptad repeats N and C. Residues in shaded regions (N terminus, GCN4 tag, and His6 tag) were not traced in the structure. (B) Cryo-EM maps of PdCoV S-e with atomic model fitted in. The maps have a contour of 6.6 σ. (C) Cryo-EM structure of prefusion PdCoV S-e. Each of the monomeric subunits is colored differently. (D) Structure of a monomeric subunit in the prefusion conformation. The structural elements are colored in the same way as those in panel A. Image and description, J Shang et al., J Virol. 92:e01556-17 (2018). © American Society for Microbiology.

The paper was published in late 2017 on the website of the Journal of Virology: J Shang, Y Zhang, Y Yang, Q Geng,W Tai, L Du, Y Zhou, W ZhangF Li. 2018. Cryo-Electronic Microscopy Structure of Porcine Deltacoronavirus Spike Protein in the Prefusion StateJournal of Virology 92 (4): e01556-17. doi: 10.1128/JVI.01556-17.

This report comes from the MSI research highlights.

 

Science Page: Actinobacillus pleuropneumoniae: a case of suspected lateral transmission (Part 2: outbreak investigation)

This is our Friday rubric: every week a new Science Page from the Bob Morrison’s Swine Health Monitoring Project. The previous editions of the science page are available on our website.

This week, we are sharing the second part of a report regarding an Actinobacillus pleuropneumoniae outbreak in the Midwest, across 3 systems and 5 farms.

If you missed part 1, you can find it here.

Key Points:

  • Communication between veterinarians and farm managers can help unravel patterns that might seem unique in one system.
  • Even though the source of APP was not determined outbreak investigation can help to find common links between sources.

A series of Actinobacillus pleuropneumoniae (APP) outbreaks involving five farms belonging to three different production companies were reported. Serotype 8 was confirmed as the source of the clinical signs in all the cases. The outbreak started with the two southernmost located farms (Company A Farm 1 and Company B Farm), followed by Company C (Farm 1) four weeks later. The distance among these growing pig sites ranged from 0.6 to 8.3 miles and the region where they are located can be considered as a high hog density area (Picture 1).

APP farm locations
Map of the farms involved in the APP outbreak

Common links between several sites were revealed after conversations among veterinarians and production managers. The main transmission route for this bacterium is introducing APP carrier pigs. In this case, it can be easily ruled out as these are sites that flow independently.

Other possibilities include indirect transmission through fomites and aerosol. Although these production companies do not share employees or tools they do have a common link in that some did share the same rendering company which could have been servicing other sites that were APP positive. As for manure removal, companies do not use the same manure removal company. One company did have the same individual doing the manure removal procedure at one site while breaking and then proceeded to the next one. Airborne transmission has been suggested as another possibility and after preliminary wind direction analyses during the outbreak dates it was inconclusive.