An outbreak of swine fever on a farm in Gifu Prefecture earlier this month seemed to come to an end after the culling of hundreds of pigs and the disinfection of all related facilities.

But the prospects of officially declaring next month the containment of the classical swine fever look increasingly dim after the virus was detected in local wild boar carcasses after the prefectural government completed the disinfection of the farm.

By Sunday, six dead wild boars that were found within a radius of 10 km from the farm tested positive for the disease.

The following are some questions and answers regarding swine fever:

What is swine fever ?

Also known as hog cholera, the viral disease is highly contagious, affecting pigs and wild boars. It does not affect humans.

Pigs can be infected by direct contact with infected swine or anything contaminated with the virus, such as vehicles and clothes. Infected pigs spread the virus via saliva, mucus, urine and feces.

Symptoms include fever, loss of appetite, discoloration of skin and constipation followed by diarrhea. Infected pigs often stay together. Many die within 10 to 30 days, according to the website of the National Agriculture and Food Research Organization (NARO).

There is no treatment. Thus to control the spread of the disease, entire herds are usually culled when an infected pig is found on a farm.

The virus can survive in pork and processed pork products for months when meat is refrigerated and for years when it is frozen, according to the World Organisation for Animal Health, or OIE.

The disease found in Gifu is called classical swine fever, which is different from the African swine fever virus that broke out in China over the summer.

Has the disease hit Japan before?

Yes. According to the Agriculture, Forestry and Fisheries Ministry, swine fever was first seen in Hokkaido in 1888. Since then, Japan has seen repeated outbreaks.

But after the introduction of a vaccine in 1969, the number of swine fever cases declined sharply. The last outbreak was in Kumamoto Prefecture in 1992.

Aiming to eradicate the disease without the use of vaccinations, the government reduced the use of shots in stages until it finally terminated them in 2006. The following year, Japan was recognized as a classical swine fever-free country by the OIE.

Where did the pigs and wild boars get the virus from? What happened at the pig farm?

The answer remains unclear.

But according to NARO’s genetic analysis, it is highly likely to have come from overseas, because the detected virus was a type of classical swine fever that was never found in Japan before.

The Gifu Prefectural Government received a report from the farm that many pigs were getting weak and dying in August, but they were diagnosed as being victims of heatstroke.

But after a positive hit resulted from genetic testing conducted on Sept. 7, the agriculture ministry conducted blood tests and confirmed there was an outbreak of swine fever on Sept. 9. About 140 pigs died at the farm, and the remaining 546 were slaughtered and buried to control the spread of the disease.

Since the outbreak, the prefectural government asked all pig farms to give a daily report regarding any hog that could be infected with the disease. So far, no cases of infection occurred within other farms in the prefecture.

Will the outbreak have a significant impact on the nation’s pork industry?

The influence is widely considered to be limited because of Gifu’s small-scale pork industry.

According to prefectural government data as of February last year, there were only 40 pig farms in Gifu, which accounted for less than 1 percent of the nation’s total. Pork production in Gifu in 2016 amounted to about ¥7.9 billion, the 21st-largest of Japan’s 47 prefectures.

The government halted pork exports across Japan following confirmation of the first case of swine fever on Sept. 9. But given that no case has been detected from other prefectures, Hong Kong, Vietnam and Macau resumed importing pork from Japan, excluding Gifu.

Japan exported about ¥1 billion worth of pork products in 2017. Hong Kong was the top importer of Japanese pork, accounting for roughly 60 percent of total exports, followed by Macau and Singapore, according to the agricultural ministry.

What’s the situation overseas?

Although Japan was listed as a classical swine fever-free country by the OIE until the recent outbreak, the disease has been endemic in Asia.

A total of 34 countries are currently recognized as classical swine fever-free by the OIE, including the U.S., U.K., Australia and New Zealand.

In the past, however, many countries that were free of the disease suffered from swine fever outbreaks, including the Netherlands in 1997, resulting in the culling of about 11 million pigs at a cost of about $2.3 billion, according to the OIE.

Apart from classical swine fever, a clinically similar African swine fever made headlines this summer as it spread rapidly in China, the world’s largest pork producer.

Given the outbreak, which resulted in the slaughtering of thousands of pigs in China, the Food and the Agriculture Organization of the United Nations (FAO) warned last month that the deadly pig virus may spread elsewhere in Asia at any time.

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