Pacific oysters in the North Island of New Zealand are being killed by a herpes virus likely dormant for years and triggered by warmer sea temperatures.

Scientists have confirmed the presence of ostreid herpesvirus-1 after some farmers reported significant losses of juvenile oysters, according to a statement today from the Ministry of Agriculture and Forestry. The disease is specific to shellfish and not related to the herpes virus that affects humans and other animals, according to the statement.

The virus has previously been linked to oyster deaths in Asia, North America, Europe and Australia, the statement said. It has killed 20 percent to 100 percent of breeding Pacific oysters in France every year since 2008, according to National Geographic’s website. New Zealand’s outbreak comes a month after a bacterial disease began spreading through the country’s kiwifruit orchards.

“There’s a lot of young oysters dying and again the virus is likely to have been kicked off by a variety of environmental factors” such as warmer oceans, Biosecurity Minister David Carter said in a telephone interview today.

The ostreid virus is likely to have been in New Zealand for “some time,” Richard Norman, the ministry’s response manager, said in the statement. While there were reports of its presence in New Zealand in 1992, the technology required to confirm the virus wasn’t available then, he said.

The disease has been confirmed in 12 farms in the North Island located in Waikato, Northland and Auckland, according to the World Organisation for Animal Health’s website. Most outbreaks were in Northland, near the top of the island.

Search for Cause

The Ministry of Agriculture and Forestry is working with the marine farming industry to establish the cause of the disease and how to manage the situation.

The virus is likely to have a “significant financial impact” on some oyster farmers in the NZ$26 million ($20 million) industry, Carter said.

“The oyster industry is clearly facing significant production issues with a predicted shortfall for next year of approximately half of next year’s harvest,” Norman said in the statement.

No problems with other oyster varieties, including Bluff oysters, have been detected and the nation’s oysters don’t face food safety concerns, according to the statement.

New Zealand aims to more than triple the size of its aquaculture industry in anticipation of a surge in global demand for seafood. The industry earns about NZ$350 million a year, or about 20 percent of the country’s seafood revenue, according to the Ministry of Fisheries.

Developing Aquaculture

The government proposed new laws last month aimed at boosting sales to NZ$1 billion by 2025 through the easing of planning and consent processes.

Almost half of Pacific Oyster production comes from Northland, the region worst affected by the herpes outbreak, according to Aquaculture New Zealand. The aquaculture industry occupies 0.02 percent of the country’s coastline. About two thirds of its total production is exported.

New Zealand’s Carter has spent much of the last month managing the outbreak of Pseudomonas syringae pv actinidiae, a bacterial vine disease discovered in 107 kiwifruit orchards. The government has said it can’t eradicate the disease and has given growers NZ$25 million in aid.