Pigs in Okinawa Prefecture may have been infected with classical swine fever through food, an expert panel commissioned by the agricultural ministry said Thursday.

Leftovers, including pork infected with swine fever in Honshu, may have caused an outbreak of the disease in Okinawa earlier this month, the panel said.

A genetic analysis conducted by the panel found that the gene type of the swine fever in Okinawa was similar to that in Gifu Prefecture and not an infection that originated overseas.

Swine fever-laced pork remains infectious for a while even after being processed into meat products unless heated sufficiently.

Such pork — from pigs resistant to the swine fever vaccine or infected with the disease but without symptoms — may have been distributed in Okinawa.

The farm where the first swine fever case in Okinawa was confirmed earlier this month fed pigs with unheated leftovers that were provided by restaurants and supermarkets.

Many farms in Okinawa feed pigs with food waste. “It’s important to be sure to heat” such feed, said Tomoyuki Tsuda, who heads the panel.

The ministry urged prefectural governments across the country to ensure pig farms heat food waste before being provided as feed. About 260 pig farms in the country use food waste as feed, according to the ministry.

At the farm where the first swine fever case in Okinawa was confirmed, the number of pigs that died has increased since late November.

One cause for the swine fever outbreak in Okinawa was insufficient disinfection of vehicles that come to and leave pig farms, the panel said.

In Japan, swine fever was confirmed for the first time in 26 years in the city of Gifu in September 2018.

The swine fever virus spread in the Kanto and Chubu regions via wild boars. No swine fever-positive wild boar has so far been detected in Okinawa.

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