Herpes virus suspected in mass carp-farm
Herpes is suspected of taking a huge toll on cultured carp in 10 prefectures,
according to findings reported Thursday to a farm ministry panel.
The first signs of carp dying were observed in fish farms in Lake
Kasumigaura, Ibaraki Prefecture, in early October. The prefecture, which
accounts for some 50 percent of farmed carp in Japan, reported that some
1,125 tons of carp had been lost as of Thursday. It said it had shipped
farmed carp to 21 prefectures.
The fish were being bred at farms in Kasumigaura and Lake Kitaura. The
dead fish were infected with the carp herpes virus.
Apart from Ibaraki, mass carp kills were reported in Aomori, Saitama,
Yamanashi, Nagano and Miyazaki prefectures. Carp kills on a smaller scale
have also occurred in Mie, Okayama, Kochi and Fukuoka prefectures, according
to the Agriculture, Forestry and Fisheries Ministry.
Of these nine prefectures, seven had received fish from Lake Kasumigaura,
and the herpes virus was found in dead fish samples in Aomori, Yamanashi,
Mie and Miyazaki. In Okayama and Kochi, however, the dead fish had been
farmed locally, indicating the possibility of another infection route.
Ministry officials said they will try to track the route of infection,
beginning by conducting hearings with fish farmers.
Officials in Mie Prefecture are reporting a loss of between one and nine
fish per day. In Okayama the losses on some days ranged between 30 and 50
fish. In Fukuoka, about two carp were dying each day, officials said. All
prefectures said they saw the phenomenon worsen around mid-October and have
issued instructions to incinerate the dead fish and refrain from shipping
The carp herpes virus, first detected in Israel in 1997, has spread to
other parts of Asia, including Indonesia and Taiwan, as well as Europe and
the United States. Infected fish stop eating and start swimming erratically,
according to experts.
It is highly contagious, but the virus does not multiply at temperatures
above 30 degrees and is not harmful to humans.
Although it has never before been detected in Japan, the agriculture
ministry listed it in June among the designated diseases under the law on
sustainable fish farming. All imported fish must be inspected for the
diseases cited under the law, but government officials said that no carp had
been imported to Japan since the change took effect.
According to the National Research Institute of Aquaculture of the
Fisheries Research Agency in Mie Prefecture, an independent administrative
institution, the disease most likely spread to other prefectures through
fish bred in Lake Kasumigaura. However, it is unclear how the virus first
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