A mysterious virus appeared in China, an infected shrimp destroyed the herd

The virus, called Div-1, has affected more than a quarter of shrimp in Guangdong, China's shrimp farming center, and is at risk of widespread infection, causing mass shrimp deaths.

Chinese shrimp farmers are witnessing day-to-day sight of a mysterious virus wreaking havoc on aquaculture farms in Guangdong province, causing the decline in production of popular seafood and tragically threatening to produce Design of tens of thousands of households.

The virus, known as Decapod iridescent 1 (Div1), was first detected in early 2014 but reappeared last spring and again in February this year, affecting About a quarter of the shrimp production area, local fishermen said.

The spread of the disease, though determined to be harmless to humans , has left the shrimp industry in Guangdong facing fears of a future that could face mass shrimp death on a scale similar to the crisis. In Africa, swine fever has eradicated 60% of pigs in China.

The Ministry of Agriculture and Rural Development reported that the DIV1 virus infects shrimp at all stages of growth and has been found to cause disease in some species of marine, brackish and freshwater shrimp.

Currently, a number of DIV1 virus-infected species have been detected, including: crayfish, whiteleg shrimp, crayfish, land lobster or freshwater lobster, river or rub shrimp and spiny lobster.

Wild wild tiger shrimp in the Indian Ocean waters are also reported to be positive for DIV1 virus.

In fact, the distribution of DIV1 viruses in the world could be much wider because it has not been specifically investigated. The transmission route has not been determined, however, the researchers said that many silk worms (used as feed for broodstock, wild shrimp) are also infected with DIV1 virus and are a potential source of disease. transmission of pathogenic viruses on shrimp.

Virus terrifying shrimp industry

"The virus's level of infection and mortality is very terrible ," said Wu Jinhong, a shrimp farmer in Da'ao Town, Jiangmen City, China.

'It only takes two or three days from the discovery of the first infection until all the shrimp in the pond die white.'

The first signs of infection are usually when shrimp start to turn red, before their shells soften and shrimp sink to the bottom of the pond , the South China Morning Post quoted local farmers as saying.

A large shrimp farming facility in China. (Artwork: Aqua Culture Alliance).

Zhong Qiang, another shrimp farmer in Zhuhai, said: 'The virus does not distinguish between species and infects both large and small shrimp, Pacific white shrimp and giant freshwater shrimp'. .

'Once a pond is infected with a virus, our farmers can hardly do anything when the risk of nearby ponds being infected just a few days later is very high , ' he said.

Scientists at the Chinese Academy of Fisheries Sciences first identified a mysterious virus in Pacific white shrimp, the main shrimp cultured in China, in Zhejiang province in December 2014.

Div1 received very little attention from the public, despite concerns in the shrimp industry that it could spread across shrimp farms in the mainland.

In 2018, the virus was found in shrimp farms and farms in 11 provinces, said Qiu Liang, a researcher at the Yellow Sea Fisheries Research Institute. The most serious outbreak hit aquaculture facilities across the Pearl River Delta last year.

In the town of Da'ao, where nearly 20,000 people - nearly half the local population - work on shrimp farms, two-thirds of the ponds were infected by the virus in the spring of 2019 and had to be drained immediately. Ie, Qiu said.

The outbreak had subsided during the summer and fall months when temperatures were higher, but returned again in February. Fishermen said temperatures above 30 degrees could stop the virus.

A stall sells shrimp in a local market in Beijing. (Artwork: Getty Images)

'This virus terrifies shrimp farmers, like bird flu for poultry farmers and swine fever in Africa for pig farmers' , said Dai Jinzhi, a fisherman who discovered 6 hectares of lake. His shrimp farming infected, sharing.

After being forced to drain water in shrimp ponds, where more than 3.7 tons of shrimp are kept, Jinzhi has only 200 kg of alive shrimp left - costing him more than 100,000 yuan ($ 14,000).

'We cannot do anything but remove shrimp and sell them at a cheap price, then drain the water from the ponds and leave them out for at least two months.'

'Some other fishermen were attacked by the virus after they started farming again in infected ponds (too early). So I don't dare to raise shrimp until the end of next month, when the weather is getting warmer. '

The risk of disease spreads when lack of necessary attention

The origin of Div1 and its transmission are still unknown , according to industry experts. As there is no effective way to prevent the spread, more and more shrimp farmers in Guangdong do not allow outsiders, including friends and family, to approach their ponds - similar to the way farmers Pigs prevent outsiders from coming near their farms due to the swine fever.

While the new infections are "thought to be mainly from local water and the environment ," Qiu said there are viruses that spread to farms through people.

However, scientists and industry groups also admit they know very little about the virus.

'As far as we know, outside of China, viruses have also emerged in Southeast Asia,' said Huang Jie, general manager of the Asia-Pacific Aquaculture Centers Network. He added that more attention must be paid to Div1 because of the threat this virus poses to shrimp production in China.

When shrimp are infected, Chinese fishermen cannot do anything but remove the shrimp and sell them at a cheap price, then empty the ponds and leave them unattended for at least two months. (Artwork: AFP).

'Extensive outbreaks can occur if there is a lack of interest from the shrimp industry and in relevant government agencies'.

It is very difficult to accurately calculate the losses caused by viruses because there is no official data or data from third parties. Normally, a shrimp pond can grow 4 waves of shrimp per year, so if only one shrimp is infected with the virus, the annual yield of the pond will be reduced by at least a quarter.

As living standards have improved in China, the demand for shrimp, lobster and shrimp has been increasing in recent years. But the domestic production of some farmed crustaceans has been affected by the Div1 virus.

Specifically, this disease has reduced Pacific white shrimp production to 1.2 million tons in 2018 compared to 1.5 million tons in 2013, the China Fisheries Statistics Yearbook 2019 for know.