Novel strategies against White Spot Syndrome Virus (WSSV): From biosecurity to RNAi and CRISPR in the shrimp industry

Since its first reported emergence in Taiwan and China in 1992, White Spot Syndrome Virus (WSSV)—one of the most hazardous shrimp diseases—has become an ongoing nightmare for the global shrimp industry. This highly virulent pathogen can cause mortality rates of up to 100% within just 7 to 10 days post-infection.

The economic losses are staggering. It is estimated that this virus alone has cost the global shrimp sector between $8 billion and $15 billion, with some annual loss estimates reaching $19 billion. Its rapid global spread—from Asia to the Americas (1995–1999), the Middle East (2001), Brazil (2005), Africa (2011), and Australia (2016)—has been facilitated by the globalization of the live shrimp trade and its waterborne transmission capabilities.

WSSV is a double-stranded DNA virus belonging to the Nimaviridae family. Its success as a pathogen lies in its ability to evade the shrimp’s immune system and replicate rapidly. Given that shrimp lack adaptive immunity (the immunological memory found in vertebrates), they rely solely on their innate immunity, which WSSV easily overcomes.

Faced with the limited success of traditional strategies and the environmental issues stemming from the inappropriate use of antibiotics (which are ineffective against viruses), the scientific community is exploring an arsenal of advanced biotechnological tools to combat this disease. In this regard, researchers from Bangladesh Agricultural University, Gopalganj Science and Technology University, and the Centre for Environment, Fisheries and Aquaculture Science (Cefas) published a scientific review offering an updated overview of the biology, pathology, transmission dynamics, and recent advancements in WSSV control measures.

Key conclusions

• White Spot Syndrome Virus (WSSV) is one of the most devastating pathogens in shrimp aquaculture, causing estimated global economic losses of $8 billion to $15 billion since its emergence.
• The virus spreads rapidly through the live shrimp trade and waterborne transmission. It can persist in pond sediments for over ten months following an outbreak.
• Shrimp lack adaptive immunity and rely on innate immunity, which is often insufficient to combat severe WSSV infections.
• Traditional control strategies (bioseguridad, selective breeding, immunostimulants) have had limited success.
• New biotechnologies such as RNA interference (RNAi), CRISPR-Cas gene editing, DNA vaccines, and nanotechnology offer significant potential for the future management and mitigation of the disease.

How is it transmitted and what does it do to the shrimp?

Understanding the biology and transmission of WSSV is fundamental to its control.

Transmission routes

WSSV has two primary modes of transmission:

1. Horizontal transmission: This is the most common route on farms. It includes:
   • Waterborne transmission: This is the most critical factor. The virus can be detected in the water just six hours after the onset of the disease in a shrimp. WSSV can remain viable across a wide range of salinities and temperatures.
   • Cannibalism: The ingestion of infected or dead shrimp.
   • Vectors and carriers: The virus has a very broad host range, infecting not only shrimp (like Penaeus monodon and Litopenaeus vannamei) but also other crustaceans such as crabs, lobsters, and crayfish. Live feeds, like copepods and rotifers, can also act as carriers.
2. Vertical transmission: This occurs when carrier broodstock transmit the virus to their progeny, representing a highly detrimental infection route in hatcheries.

Pathology: The signs of the disease

The most characteristic (pathognomonic) sign of WSSV is the presence of white spots on the exoskeleton (cuticle), particularly on the cephalothorax. These spots are calcium deposits resulting from the virus’s pathology.

However, it is crucial to note that not all WSSV infections present with white spots. Other clinical signs include:

• Lethargy and reduced feeding.
• Erratic swimming or movement toward the pond edges.
• Reddened or discolored bodies.
• Soft shells.

At the histopathological level, WSSV primarily attacks tissues of ectodermal and mesodermal origin, such as the cuticular epithelium, gills, and lymphoid organ. The infection causes cell nuclei to hypertrophy and fill with viral inclusion bodies, leading to widespread necrosis and organ failure.

The challenge of co-infections

A growing problem in shrimp farming is that WSSV rarely attacks alone. Co-infections, where two or more distinct pathogens infect the shrimp simultaneously, are becoming increasingly common.

Studies have demonstrated that WSSV has synergistic interactions with other significant pathogens, such as:

• Infectious Hypodermal and Hematopoietic Necrosis Virus (IHHNV).
• The microsporidian Enterocytozoon hepatopenaei (EHP).

This synergy means that the presence of EHP, for example, can increase the severity of or susceptibility to WSSV, greatly complicating diagnosis and disease management in the ponds.

Innovations in WSSV control

Conventional measures, such as improving biosecurity and selectively breeding for resistant shrimp, have shown limited success. Therefore, research has focused on new biotechnologies to bolster the shrimp’s immunity and directly attack the virus.

Immunostimulants and Probiotics

The use of immunostimulants and probiotics aims to strengthen the shrimp’s innate immune system. Various natural substances have demonstrated potential:

• Algal extracts: Compounds like fucoidan (from brown algae) and sulfated galactan (from red algae) have been shown to enhance the immune response (increasing hemocytes, prophenoloxidase activity) and even block viral entry by interacting with its envelope proteins (VP26 and VP28).
• Probiotics: Bacterial species such as Pediococcus pentosaceus, Lactobacillus, and Bacillus spp. improve gut health and strengthen the immune response, reducing post-infection mortality from WSSV.
• Bioactive compounds: The dietary inclusion of flavonoids (like quercetin) and carotenoids has been shown to reduce viral load and upregulate immunity-related genes.

Nanotechnology: Detection and delivery

Nanotechnology offers solutions for both diagnosis and treatment.

• Rapid detection: Methods are being developed that use gold nanoparticles (GNPs) for visual, field-level detection of WSSV, achieving sensitivity similar to qPCR but in only 30 minutes.
• Treatment: Silver nanoparticles (PVP-AgNPs) have shown anti-WSSV activity in vitro by inhibiting viral adhesion.
• Delivery vehicles: Perhaps its most promising application is the use of nanoparticles (such as polyanhydride) or Virus-Like Particles (VLPs) to protect and administer RNAi (dsRNA) vaccines orally or via immersion.

DNA Vaccines and RNA Interference (RNAi)

Given that shrimp lack adaptive immunity, traditional vaccines do not function the same way. However, nucleic acid vaccines are showing promising results.

• DNA vaccines: The use of DNA encoding key viral proteins, such as VP28, has been shown to improve immune enzyme activity and increase shrimp survival.
• RNA Interference (RNAi): This is one of the most potent strategies. It involves introducing double-stranded RNA (dsRNA) that matches vital WSSV genes (like VP19, VP28, rr1, and rr2). This activates the shrimp’s natural machinery to “silence” or destroy the virus’s messenger RNA, drastically inhibiting its replication. The primary challenge for RNAi remains the effective delivery and stability of dsRNA in water, an area where nanotechnology is key.

Gene Editing (CRISPR-Cas)

The CRISPR-Cas gene-editing tool opens the door to precise genomic modification to create WSSV-resistant shrimp. Research is focused on editing the shrimp’s own immune-suppressing genes (like GIH and MIH) to promote greater immunity. Although it is a fascinating technology, its practical application in aquaculture still faces significant technical and ethical hurdles.

Conclusion: Toward a convergent management approach

WSSV remains the most destructive viral pathogen in global shrimp farming. The study of its biology, pathology, and transmission mechanisms demonstrates that no single solution exists.

The successful management of the disease in the future will not depend on a “silver bullet” but rather on a convergent approach. This involves integrating enhanced biosecurity with the strategic use of immunostimulants, probiotics, and new biotechnologies, such as RNAi vaccines administered via nanotechnology.

For these laboratory innovations to reach the field, interdisciplinary collaboration is required among researchers, the industry, and policymakers, ensuring that shrimp aquaculture can grow sustainably and resiliently.

Reference (open access)
Iftehimul, M., Hasan, N. A., Bass, D., Bashar, A., Haque, M. M., & Santi, M. (2025). Combating White Spot Syndrome Virus (WSSV) in Global Shrimp Farming: Unraveling Its Biology, Pathology, and Control Strategies. Viruses, 17(11), 1463. https://doi.org/10.3390/v17111463 https://www.mdpi.com/1999-4915/17/11/1463

Milthon Lujan

Editor at the digital magazine AquaHoy. He holds a degree in Aquaculture Biology from the National University of Santa (UNS) and a Master’s degree in Science and Innovation Management from the Polytechnic University of Valencia, with postgraduate diplomas in Business Innovation and Innovation Management. He possesses extensive experience in the aquaculture and fisheries sector, having led the Fisheries Innovation Unit of the National Program for Innovation in Fisheries and Aquaculture (PNIPA). He has served as a senior consultant in technology watch, an innovation project formulator and advisor, and a lecturer at UNS. He is a member of the Peruvian College of Biologists and was recognized by the World Aquaculture Society (WAS) in 2016 for his contribution to aquaculture.