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Today, I am going to share you some of the important information about Scale Drop Disease Virus infection in Asian Seabass.It is well recognized how important the Asian seabass has become nowadays.
- Improvement of broodstock
- Implementation of best aquaculture practices
- Development of hatcheries and all these leads to better seed and better farming.
Whatever we do, casualities will always happens in farming. We must ensure to combat these challenges by improving maintainance, collaboration, survivellence and so on..
In this row, one of the serious threats caused by SDDV in asian seabass is inevitable one. Let's jump into the topic to get important information about this virus.
About the virus:
SDDV is a double-stranded DNA virus belonging to the genus Megalocytivirus within the family Iridoviridae. This virus causes significant mortality, primarily in Asian seabass (Lates calcarifer), across South and Southeast Asia. The disease was first reported in farmed Asian seabass in Singapore and has since become more prevalent and confirmed in other Southeast Asian countries.
Signs & symptoms:
The prevalence of SDDV infection is higher during the monsoon season, particularly under conditions of heavy rainfall and low salinity. This virus mostly transmitted by horizontal transmission.
Image 2 source:M. Nurliyana et al.,2020 (First evidence of scale drop disease virus in farmed Asian seabass (Lates calcarifer) in Malaysia)
Infected fish typically exhibits,
- Lethargic swimming
- Darkening of the dorsal body region
- Severe scale loss
- Reddening of the ventral side
- Hemorrhagic lesions.
First report on histopathology:
The first report by S. Gibson-Kueh et al. described several pathological findings in SDDV-infected Asian seabass.
Multiple necrotic lesions were observed in the dermis layer of the skin, associated with vasculitis in the necrotic areas. Necrosis was also detected in the spleen, kidney, and eye, indicating the pathogenicity of the virus. The presence of multifocal encephalomalacia in the brain may be responsible for the abnormal spiral swimming behavior.
Basophilic cytoplasmic inclusions were observed in the spleen, kidney, liver, and heart, while karyolysis was detected in hepatocytes of the liver.
Prevention & treatment:
Nowadays, Vaccines giving promising results in disease prevention in tropical and cold water fish. Vaccine development is considered one of the most effective strategies to control SDDV infection in Asian seabass.
Although inactivated vaccines are widely used for prevention, sometimes they fail to provide long-lasting immune protection, resulting in poor humoral and mucosal immune responses. To overcome these limitations, research is focusing on the development of vaccines utilizing protein nanoparticles and other advanced approaches. Some studies have also demonstrated immune responses against SDDV following immunization with a formalin-killed SDDV vaccine, showing upregulated gene expression and immunological memory. So, vaccines are best alternative that everybody in the industry should aware. Try to utilize resources to increase your production and serve the world with best protein.
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Thank you,
Dhivagar P
dhivagarfcri2000@gmail.com
References:
https://doi.org/10.1016/j.aquaculture.2022.738993
Hi Dhivagar,
ReplyDeleteThis post is really informative and well-written! Loved how clearly you explained about the SDDV. Keep up the great work — this kind of content truly helps others learn. 👍