Decapod Iridescent virus 1 (DIV1)

Shrimp get sick too. Decapod Iridescent virus 1 (DIV1) is a recently emerged infectious agent causing high mortality in Penaeus vannamei. DIV1 can affect late-postlarvae, juvenile and subadult shrimp, mainly during low temperature seasons. The very recent emergence of the virus has not allowed sufficient research to link external effects such as environmental, nutritional, physiological or pathological stressors to influence the susceptibility and level of mortality of the viral disease. The main target organs for DIV1 infections are hematopoietic tissue, gills and hepatopancreatic sinuses. High mortality of up to 80% has been reported in farmed P. vannamei.
DIV1 virus has additionally been detected in wild specimens of P. monodon caught in the Indian Ocean. As with other pathogens, it is thus highly recommended to screen every batch of wild-caught P. monodon broodstock destined for use in commercial shrimp aquaculture facilities for DIV1 viral load by molecular based tests like PCR.
The Shrimp MultiPath Xtra PCR test will help to confirm DIV1 infections as well as provide information to producers about presence and/or absence of this virus and other shrimp pathogens frequent in culture systems, in a precise, reliable and quantitative way (number of pathogens per sample).

Causative agent of Decapod Iridescent virus 1 Disease. Originally called Cherax quadricarinatus iridovirus (CQIV) or Shrimp Hemocyte Iridescent virus (SHIV) and now classified within the proposed genus Decapodiridovirus within the family Iridoviridae, was first reported in juvenile White shrimp P. vannamei and crabs in Chinese aquaculture settings in 2014. DIV1 has a characteristically large icosahedral shape that can reach a diameter of around 150 nm. The virion particle contains a linear double-stranded DNA. This family of viruses has a broad spectrum of hosts including invertebrates (insects) and poikilothermic vertebrates (fish, amphibians, and reptiles).

Whilst the virus has no impact on human health or food safety, and any affected shrimp are safe for human consumption, it does have a significantly detrimental effect for shrimp farmers, due to massive mortalities.

Shrimp species susceptible to DIV1 infection include penaeid shrimp such as P. vannamei, P. monodon and P. chinensis. The virus has also been detected by PCR in frozen samples of krill and polychaetes from China, as well as in freshwater shrimp Macrobrachium rosenbergii. The screening and detection of DIV1 in shrimp broodstock feed is critical, as it will enable farmers to only feed high-quality virus free polychaete feed to shrimp and avoid infection of postlarvae by vertical transmission from feed to shrimp.
Clinical signs of DIV1 in Penaeid shrimp are hepatopancreas atrophy with pale or yellowish discoloration, and empty stomach and midgut. Additionally, some dying shrimp show slightly whiteish coloration of the abdominal muscle as shown in the image right. Shrimp MultiPath Xtra PCR is able to confirm DIV1 infections whilst also giving information on the presence and /or absence of other pathogens in the culture system, in a quantitative manner.

Reference: https://genics.com.au/wp-content/uploads/2020/08/Genics-DIV1-Educational-Resource-Guide.pdf?x60024

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