The current situation
On September 20, 2019, the Japanese government said it will shift its policy and allow the vaccination of domestic pigs to try to curve the spread of Classical Swine Fever (CSF) in the country. The virus re-emerged in September 2018 after 26 years of the country being considered free of the disease. The virus, which was first found in a farm in central Japan, has since spread to four surrounding prefectures.
CSF, also known as hog cholera, is a contagious viral disease of domestic and wild pigs. The virus is considered a foreign animal disease (FAD) and identification of this disease must be reported to the OIE. The virus is transmitted through direct contact via saliva, nasal secretions, urine, and feces. However, contact with contaminated vehicles, pens, feed, or clothing may spread the disease. Humans are not affected by the virus.
The ministry has been hesitant to vaccinate commercial farms as a means to control the spread due to the impact on pork exports (vaccine use would prevent Japan from regaining its OIE status as a country free of the disease); however, the Chief Cabinet Secretary said that “Japan now faces a significant phase in coping with the epidemic and will endeavor to promptly address the issue, including how to respond to the possible impact on exports.” Japan currently has enough vaccines to vaccinate about 1 million pigs, but has asked makers of livestock drugs to boost production of the CSF vaccine as the disease has spread to the eastern area, one of Japan’s main pork-producing regions.
Expert Interview: Dr. Satoshi Otake
During the 2019 Leman Conference, the University of Minnesota was able to catch up with Dr. Satoshi Otake to discuss the current situation of CSF in Japan. Dr. Otake is the owner/CEO of Swine Extensions and Consulting, Inc., a board member of JASV (Japanese Association of Swine Veterinarians), and a partner of SDEC (Swine Disease Eradication Center) of University of Minnesota.
Dr. Otake started by mentioning the index case of CSF that first appeared in Gifu province. He said that they were able to isolate the virus and after sequencing it and determined that the strain is different from the infectious strain 26 years ago. Although it remains unclear how the virus entered the country, the strain was identified to be very similar to the current strains circulating in China. It is speculated, though, that the index farm got infected directly or indirectly though wild boar.
The current control strategies by the ministry are:
- Stamp-out infected premises and restrict pig movement.
- Encourage producers to focus on biosecurity for farms.
- Encourage producers to set up fencing in order to prevent the introduction of wild boars and other wild animals.
- Government use of oral bait vaccines for wild boar in affected prefectures
- Encourage producers who are located in very high-risk areas to voluntarily vacate the premises.
“JPPA (Japanese Pig Producer Association) and JASV (Japanese Association of Swine Veterinarians) have suggested that our government enhances vaccination for the wild boar population, and to make a decision for regional vaccination of commercial pig farms for a limited period of time,” Dr. Otake highlighted. In this regard, the use of a marked vaccine that would allow differentiating vaccinated from infected animals is under discussion. This tool would be extremely useful to implement effective surveillance activities required for a vaccination program in specific zones, without affecting the status of free without vaccination as recognized by the OIE for the rest of the country.
CSF is difficult to control
What is troubling though, is despite Japan’s effort to control the disease for over a year using recommendations outlined by the OIE and other experts, Japan has still not managed to control the disease. Dr. Otake indicated that one of the reasons that CSF may be difficult to control is that there still is not a clear idea of how it is spreading. He says it could be due to wild boar, vehicles, and animal or feed movements. Other challenges he discussed that have been difficult for control is the fact that the virulence of the virus is quite low. Dr. Otake points out that with the CSF strains circulating in the country, it is difficult to detect the clinical signs early in a barn due to its low virulence. This makes early diagnosis and control challenging.
Finally, we asked Dr. Otake what lessons have been learned that could be shared with swine practitioners in the US and other countries to be prepared for CSF. He said that it is important to collaborate with government agencies when these diseases are suspected or arise because as private practitioners, we do not have the authority to make any decisions regarding FAD strategies and controls. However, he does point out that private practitioners can make significant influences on it.
Producers should take note that it can be difficult to detect clinical signs in barns early, so as not to rely on this for control. Farmers should constantly be vigilant, and biosecurity is the most important piece in the puzzle. He also stated that strategies used to control PRRS and/or PED can be expanded to control for other FAD including CSF. He closed by warning that ASF could be coming next and that all must be prepared.
Since interviewing Dr. Otake, Japan has released a statement that they will begin vaccinating commercial pigs for CSF as current control efforts are not succeeding.
Questions, comments, feedback about today's Weekly Update? Please email Dr. Gus Brihn.
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Gus Brihn
Gus completed his undergraduate degree at the U of M in Global Studies, and has spent much of his time abroad, including time in France and Namibia. Gus became interested in emergency medicine from becoming a Wilderness First Responder and NR-EMT. He completed his veterinary degree at the University of Glasgow in Scotland. Gus is interested in zoonotic disease outbreak investigation, prevention, and epidemiology. Outside of work, Gus enjoys rock climbing and doing Brazilian Jiu jitsu. He has an 11 year-old Staffordshire terrier mix breed dog named Sweet Pea.