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Biosecurity is Key to Battling Foreign Swine Diseases

By: Diane DeWitte, Swine Extension Educator
Originally printed in The Land - August 24/August 31, 2018

In animal agriculture, especially when we speak about biosecurity, we encounter an alphabet soup of diseases: PRRS (Porcine Reproductive & Respiratory Syndrome), PEDV (Porcine Epidemic Diarrhea Virus), SVA (Seneca Virus A) and more.

The broader scope includes the category FAD (Foreign Animal Disease), and the three that we do not have in this country: Classical Swine Fever (CSF), Foot & Mouth Disease (FMD) and African Swine Fever (ASF). These three foreign animal diseases are the ones for which the US swine industry is putting together a nationwide strategy of movement and containment, the Secure Pork Supply.

Swine Disease in China
Recently African swine fever made an appearance, and not in a good way. On August 3, 2018, a small pig farm in northeastern China was confirmed as infected with African swine fever. The Chinese Center for Disease Control and Prevention reported that on the farm with a population of 383 pigs where 47 died, the outbreak was contained with the slaughter of nearly 1000 pigs from that herd and neighboring area. Live pig transportation and transfer of related products from that area has ceased, and feeding of untreated food waste has been banned.

This ASF outbreak causes concerns on many levels:

1) The infected farm’s location is 130 miles from the North Korean border and 800 miles from Japan. The distinct fear of spreading the disease across China and to other parts of Asia has Chinese authorities working to control pig movement nationwide.

2) China is not only the world’s top consumer of pork, but its numerous backyard and large-scale pig farms raise more than half of the global hog population.

3) Current ASF outbreaks in Latvia, Romania, the European Union’s Baltic States, and the Russian Federation are thousands of miles away from the northeastern Chinese pig farm. How did it get there?

An Unknown in the US
African swine fever has been a fixture in sub-Saharan Africa and, at different times, found in Europe, South American and Caribbean. In the 1960s in Spain and Portugal, complete eradication took 30 years. ASF is caused by the long-lived African swine fever virus which persists in pig products and the environment. It is the only DNA virus transmitted by arthropods. It has an incubation period of 5 to 19 days after contact with an infected animal. ASF can be very acute, and naïve domestic pigs will experience 100% mortality. Symptoms include fever, dark blotching on ears, tail, lower legs and ham, weakness, diarrhea, and hemorrhages. Less virulent infections will result in coughing, emaciation, swollen joints and ulcers on the skin. Currently there is no vaccine against African swine fever.

The disease affects members of the pig family (Suidae). Symptomatic infections occur in domestic swine, feral pigs, and European wild boars. ASF infections which show no symptoms are found in warthogs, bush pigs, giant forest hogs in Africa, and they are considered the reservoir of the virus. In South America, peccaries (Tayassu species) are also a non-symptomatic carrier of the virus. African swine fever can be spread by direct contact with infected animals, on equipment or clothes, and by soft ticks. In Africa, infected soft tick colonies living in pigs’ burrows can repeatedly pass ASF virus to baby warthogs and back, and maintain the virus for years.

African swine fever’s current appearance outside of Africa was in 2007 in Georgia. It quickly spread throughout the Russian states and eastern Europe, and it has moved rapidly through both domestic pig populations and wild boar herds.

ASF in Research
Following the 2013 outbreak of Porcine Epidemic Diarrhea Virus (PEDV) in the US, researchers began to explore how the disease might have gotten into the North American pig population. Scott Dee, director of research at Pipestone Veterinary Services here in Minnesota worked with Diego Diel at South Dakota State University and Megan Niederwerder at Kansas State University’s Level 3 biosecurity lab to evaluate the potential for viruses to move around the world in feed ingredients.

The team developed a model to determine the ability of 10 viruses to survive a 37-day journey on a ship from Beijing, China to Des Moines, Iowa. Kansas State University evaluated whether the African swine fever virus would survive a 30-day journey from Warsaw, Poland to Des Moines. The Iowa city was selected as a central location where feed would be mixed and sent to pig farms across the Midwest.

The team’s previous studies had shown that PEDV could survive a trip from China in five feed ingredients—vitamin D, lysine, choline and both organic and conventional soybean meal. Similar feed ingredients were used in the most recent research, and dog and cat food along with sausage casings of pork origin were also evaluated. Complete results of the study were published in March 2018 in the journal PLOS ONE, and can be found here: https://z.umn.edu/VirusSurvival

Various viruses survived in some feed ingredients and not others, with Dee finding that feed ingredients with high plant protein and low fat posed the highest risk for virus survival. Soy oil cake is imported from China in the largest amounts of any of the tested ingredients, and only four viruses survived the simulated journey. Only two viruses survived in DDGS, and four viruses survived in the sausage casings, another increasingly imported ingredient.

African swine fever, however, survived in eight ingredients. In addition, ASF virus was the only virus which survived the 30-day journey on its own, without a feed ingredient.

Currently Drs. Perez and VanderWaal with the University of Minnesota Veterinary swine group are conducting research to model and analyze the epidemiology of Foot and Mouth Disease and African swine fever, to improve decisions which need to be made to prevent and control these foreign animal disease.

Back to Biosecurity
If it’s possible to have a bright spot, the one to recognize during the catastrophic loss of 7 million North American baby pigs in the winter of 2013-2014 was this: Producers immediately tightened their biosecurity practices, and many were able to evade the disease. Some anecdotal evidence suggested that other swine diseases may have been diminished or avoided that winter because of pig farmers’ strict attention to biosecurity.

Biosecurity is effective and it will be one key way to prevent the spread of a very persistent foreign animal disease like African swine fever. The ASF virus is highly resistant to environmental conditions. It can survive a year-and-a-half in blood stored at 39 degrees F, 11 days in feces at room temperature, and at least a month in contaminated pig pens.

Implementing a detailed biosecurity plan and following it to the letter is the important management tool to avoid foreign animal diseases. Swine producers can prepare for a disease outbreak by voluntarily participating in the Secure Pork Supply initiative. Through SPS, farmers can map their farm, connect with the MN Board of Animal Health, and plot their livestock movement alternatives in the case of a catastrophic disease outbreak. Dr. Dave Wright is the MN coordinator of the Secure Pork Supply program. (wright2me.dave@gmail.com) Producers can contact Dr. Wright or the University of Minnesota Extension swine educators Sarah Schieck (schi0466@umn.edu) or Diane DeWitte (stouf002@umn.edu) for details to get started on a Secure Pork Supply plan for their farm.

Diane DeWitte is a UM Extension Swine educator located in Mankato. She can be reached at stouf002@umn.edu.

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