New shrimp disease on its way originated in China.
A deadly viral disease Decapod iridescent virus –DIV1
A new virus is decimating shrimp farms in China's Guangdong province, called Decapod iridescent virus 1 or DIV-1 which was first detected in early 2014. It reappeared with vengeance in last spring and again in February 2020, affecting about a quarter of the area under Shrimp production in South China.
This virus is called iridescent as it discharges a typical light . It is not known to harm humans, but can kills shrimp in a matter of days, This disease is also known as
Whitehead disease (WHD).
Decapod iridescent virus 1 (Div1) was reported in Chinese province of Guangdong, putting many shrimp farmers’ livelihoods at risks. A chinese farmer Wu Jinhong told to South China Morning Post, that virus is extremely virulent.The infection rate and lethalness of the virus are terrifying. It only takes two or three days from detecting the first infection for all shrimp in the pond to be killed.”
The virus has been impacting both Pacific whitleg shrimp (Litopenaeus vannamei) and giant river prawns (Macrobrachium rosenbergii) causing their shells to become reddish in colour, then soften and it has been reported to spread rapidly to surrounding ponds. Previous outbreaks of the condition, which was first detected in China in 2014, have eased with the onset of summer, when water temperatures have topped 30°C. “This virus is horrifying shrimp farmers, like avian flu did to poultry farmers and African swine fever to those raising pigs,” Dai Jinzhi, another farmer who found out recently his six hectares of ponds were infected, told the South China Morning Post. After he was forced to drain his enclosures to fallow them and remove the disease only 200 kg of the 3,700 kg were left alive - in financial terms a loss of more than 100,000 yuan (US$14,000).
China's shrimp farmers 'terrified' as deadly virus threatens to destroy lucrative seafood industry The virus, known as Decapod iridescent virus 1, has infected about a quarter of the shrimp farms in Guangdong province, the heart of production in China
It was published in China Economy recently that a deadly virus i.e. Decapod iridescent virus (DiV1) has infected about a quarter of shrimp farms in Guangdong province, slashing the output of popular seafood and threatening the livelihood of thousands of households in China. This disease first reported in China and later in Thailand Shrimps which affected with this disease suffer huge mortalities within 2-3 days of onset of symptoms and posing threat to Litopenaeus vannamei and Macrobrachium rosembergi (Scampi) and also to few other penaeid species. This virus was firstly identified into the Claw Cray fish (Cherax quadricarinatus) and it is called as cherax quadricarinatus iridescent virus (CQIV).The disease was transmitted from the adjacent pond stocker with P. vannamei. The outbreak of infection was due to prawn which has slightly whitish muscle and mutilated antenna
Signs at the farm, tank or pond level include:- lethargy, cessation of feeding, diseased shrimp sinking to the bottom of the pond, high mortalities occurs in late-post larvae, juvenile or sub adult prawns.
Gross pathological signs :
Empty stomach and gut, soft shell, mutilated antennae, whitish to yellowish coloured head caused by a pale atrophied hepatopancreas, white triangle under the carapace at the base of the rostrum.
Clinical symptoms of M. rosenbergii(20180620) naturally infected with DIV1. (A) Overall appearance of a diseased prawn in water. (B) Close-up of cephalothoraxes. Blue arrows show white area under the cuticle at the base of rostrum. White arrows indicate hepatopancreas atrophy, color fading, and yellowing.
As per the NBFGR, the viral disease is not yet reported in India and also not included in the OIE listed diseases so far.
SPECIES AFFECTED TILL DATE :-
Pacific white shrimp (Penaeus vannemei)
Red claw cray fish
Red swamp cray fish (Procambarus clarkii)
HOW IT SPREADS TO THE OTHER COUNTRIES:-
The spread of the disease, has left the shrimp industry in Guangdong concerned, as it is facing mass deaths in Shrimp ponds nearby too.
It only takes two or three days from detecting the first infection in the pond.
The virus will spread through the brood stock to other countries.
This also spread from pond to pond with the help of vectors and by transferring the live species.