Updating Japan's Classical Swine Fever Outbreak

Original Map Credit Wikipedia

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Last September - roughly a month after China announced their first outbreak of African Swine Fever (ASF) - Japan announced the discovery of Classical Swine Fever (CSF) in Gifu Prefecture (see Japan: MAFF Confirms Classical Swine Fever Outbreak).

Often clinically indistinguishable from African Swine Fever (ASF), Classical Swine Fever is caused by a different virus (genus Pestivirus, family Flaviviridae).

Both diseases are highly contagious, and can be economically devastating for pork producers, but neither disease is considered zoonotic threat. Japan had been one of only 35 countries (see map below) that has been certified by the OIE as being free of the disease with their last outbreak reported in the early 1990s.

 With Japan's recent suspension, that number now stands at 34.

Until late December, Japan's CSF outbreak had been limited to a half dozen farms (see  A 6th Farm Outbreak Of Classical Swine Fever) and scores of wild boar, all located within Gifu Prefecture.  On December 25th, a the OIE reported (See Follow-up #10) finding the virus in a wild boar in neighboring Aichi Prefecture.

On the 21nd of December, Aichi Central LHSC found samples derived from a wild boar captured in Aichi prefecture, next to Gifu prefecture, to be positive by RT-PCR for CSFV. NIAH conducted gene sequencing and found the samples to be positive. 20 wild boars (7 dead and 13 captured) in Aichi prefecture have been tested and 1 was found to be positive for CSF by RT-PCR since 14th of September.

Yesterday, in the OIE's Follow-up #13, 9 more wild boar from Gifu and Aichi Prefectures were reported positive for the CSF virus, bringing the combined total to 103 (not including farm losses).

1. Summary of the wild boar surveillance: As of the 21st of January, 670 wild boars (69 dead and 601 captured) in Gifu prefecture have been tested and 97 (34 dead and 63 captured) were found to be positive for CSF by RT-PCR since 13th of September. 

50 wild boars (11 dead and 39 captured) in Aichi prefecture have been tested and 6 were found to be positive (1 dead and 5 captured) for CSF by RT-PCR since 14th of September. 

Among the other prefectures, 151 dead wild boars in 36 prefectures were tested and all were found to be negative by RT-PCR since the 14th of September(*). (*): All prefectures are requested to conduct CSF testing on dead wild boars.

Even as Japan attempts to contain this outbreak of CSF, they are keeping a wary eye on the spread of African Swine Fever in nearby China - and like many other Asian nations - are taking steps to try to prevent its import (see China MOA Denies ASF `Epidemic' While Taiwan Increases Interdiction Efforts).

While eradicating CSF is a big job, Japan managed to do so nearly 3 decades ago. In 2007 MAFF produced the following summary:

The eradication of classical swine fever in Japan

Classical swine fever, which is an acute infectious disease in pigs, existed throughout Japan but the outbreaks had decreased sharply with the improvement of the disease control and herd management technologies and the implementation of a live vaccine from 1969. No outbreak has been observed since 1992.

Under such circumstances, eradication program has been introduced step by step since 1996 to establish control measures without vaccination and thus to fully eradicate this disease with the cooperation of prefecture and local governments, producers and all other related organizations.

As a part of the measures, we have completely banned vaccinations since April 1st, 2006, and watched the disease. One year had passed since then and we had reported the achievement of the eradication program to the Office International des Epizooties (OIE). According to the requirement of the OIE code, Japan had become a classical swine fever free country on April 1st, 2007.