Classical Swine fever, more commonly known as hog cholera, has been identified on a farm in Japan. It has been 26 years since that country has had an outbreak of the devastating virus.
“On Sunday September 9th, Japan reported the occurrence of Classical Swine fever, in a farm located at Gifu Prefecture, in the central area of the country,” says a report from the Swine Health Information Center (SHIC) on Monday morning. “Last week, one pig died suddenly, followed by the mortality of 80 others. On Sunday, officials declared the animals as tested positive for Classical Swine fever (CSF), also known as Hog Cholera.”
This occurrence is unrelated to the African Swine Fever (ASF) epidemic in China and other countries in Eastern Europe. SHIC reports that Japanese Veterinary Services have ruled out the occurrence of African Swine Fever (ASF) in this outbreak or in the country.
What is Classical Swine Fever?
Like ASF, CSF does not impact people, however it can be devastating to the pork industry because pork sales would be severely disrupted. The Merck Veterinary Manual’s description of Classical Swine fever follows:
Classical swine fever is a contagious, often fatal, disease of pigs clinically characterized by high body temperature, lethargy, yellowish diarrhea, vomiting, and a purple skin discoloration of the ears, lower abdomen, and legs. It was first described in the early 19th century in the USA. Later, a condition in Europe termed “swine fever” was recognized to be the same disease. Both names continue to be used, although in most of the world the disease is now called classical swine fever (CSF) to distinguish it from African swine fever (see African Swine Fever), which is a clinically indistinguishable disease but caused by an unrelated DNA virus.
CSFV is moderately fragile and does not persist in the environment or spread long distances by the airborne route. However, it can survive for prolonged periods in a moist, protein-rich environment such as pork tissues or body fluids, particularly if kept cold or frozen. Virus survival times up to several years have been observed in frozen pork meat. CSFV may also survive months in chilled or cured cuts.
Immediate Action in Japan
SHIC reports that a task force was implemented, and the remaining 610 pigs on the farm were culled to contain the outbreak.
By Monday morning (local time), depopulation of the farm was completed, the news report from SHIC said. It added that no clear origin of infection was identified. The farm obtained commercial feed, and it was reported that there were no known foreign laborers or visitors from countries endemic with CSF working in the farm. Cause of the virus introduction is “unknown and under investigation.”
“Exports of pork have been suspended until the Veterinary Services are capable of understanding the extent of the outbreak and if the measures were sufficient to contain it, while investigations about possible routes of introduction are implemented as well,” SHIC said. “The Gifu Prefecture is not the major area of swine production, and it is located 500 miles (800 kilometers) from the south region, the highest pig-dense area.”
Figure 1: Map of Japan, and Prefectures. In red, location of the Gifu Prefecture, in Central Japan. The highest pig-dense area of Japan is located in the south region of the country (adapted from Sasaki et al.,2017) approximately 500 miles (800 km) from Gifu Prefecture by road.
“CSF is a notifiable disease and affects the international trade of pork, however, clinically it is usually considered less severe than ASF,” SHIC said. “Currently, it is considered endemic in many countries, including China, therefore it is a disease with potential direct and indirect effects to the U.S. industry. Depending on the strain, extensions of outbreak, route of introduction and effectiveness of biosecurity measures to contain and prevent re-introductions, it could offer different levels of risk.”
Unlike ASF, commercial vaccines are available for the control of CSF.
U.S. Industry Taking Measures
Last week, the National Pork Producers Council (NPPC) hosted a meeting with the American Association of Swine Veterinarians, National Pork Board, the Swine Health Information Center and the U.S. Department of Agriculture, including U.S. Chief Veterinary Officer Jack Shere, to discuss the threat of and protect America’s pork producers from foreign animal diseases (FADs), NPPC said in its weekly Capital Update. It also is encouraging U.S. producers to take extra precautions to protect their herds with increased biosecurity measures.
“To support the effort to prevent FADs, NPPC is asking for mandatory funding as part of the 2018 Farm Bill of $150 million for a vaccine bank to deal with an outbreak of Foot-and-Mouth Disease, $30 million for the National Animal Health Laboratory Network, which does animal disease diagnostics, and $70 million in block grants for state animal-health agencies for efforts to prevent diseases,” NPPC said.
CSF Background in Japan
According to SHIC, the last CSF outbreak in Japan was in 1992 in Kumamoto Prefecture. In 2007, the use of vaccination was banned, and disease eradication was declared in the country.
"The Japanese swine industry is still recovering from the 2013-2016 PED epidemic,” SHIC said. “On July 9th-2018, APHIS published the official notice of the OIE recognition of Japan as free CSF. Currently, Japan exports pork, and it is in the top-10 pork producing countries in the world. FAS/Tokyo estimates Japanese swine slaughter held stable at 16.336 million head in 2017.”
At this point, no other cases of CSF are suspected in Japan, but the status won’t be known until additional testing is completed.
Figure 2: Report of classical Swine Fever in Japan. In red, Gifu Prefecture in Japan, located in the central area of the country. Score 2.
Japan’s “Significance” Score
The “SDGS - Significance score” is a scoring system to assess the likelihood a disease event will impact the global swine industry, SHIC reported. Scores range from 1-3 (low-high) based on the novelty of the disease, effect on the swine industry, and impact on trade. Presently, Japan has a score of 2.
Dr. Yosuke Sasaki, University of Miyazaki, and Dr. Satoshi Otake, Swine Extension & Consulting, Inc., Japan.
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