Tilapia Lake Virus Pathogenesis and Aquaculture Impacts

Tilapia lake virus (TiLV) is a segmented, negative-sense RNA virus that has emerged as a major pathogen of farmed tilapia over the past decade. Its ten‐segment genome encodes unique proteins, among them an orthomyxo‐like RNA‐dependent RNA polymerase and a nucleoprotein that together orchestrate viral replication. Infection is systemic, targeting organs such as liver, brain, spleen and gills, and manifesting clinically as lethargy, skin haemorrhages and neurological signs. Mortality rates often exceed 80 per cent in naïve stocks, inflicting severe economic losses, trade restrictions and threats to food security in low‐ and middle‐income countries. Pathogenesis involves viral entry via mucosal surfaces, rapid genome replication and evasion of host immune responses, culminating in tissue necrosis and organ failure. Control measures in aquaculture currently rely on stringent biosecurity, early detection and selective breeding for resistant strains, while research continues to pursue antiviral compounds and vaccine candidates to mitigate the global impact of TiLV.

Research from Nature Portfolio

Recent structural studies have illuminated the architecture of the TiLV polymerase, revealing a compact heterotrimeric complex that retains core domains characteristic of orthomyxoviruses despite a 40 per cent reduction in overall size. High‐resolution cryo‐electron microscopy captured polymerase conformations in pre‐initiation, initiation and elongation states, detailing how the enzyme engages viral RNA promoters and transitions between transcriptase and replicase modes. Intriguingly, the endonuclease‐like domain appears inactive and the cap‐binding site is autoinhibited, suggesting unconventional mechanisms of host mRNA cap snatching. These insights not only deepen our understanding of TiLV replication but also identify novel structural features that may be exploited in the design of targeted antivirals.

Tilapia Lake Virus Pathogenesis and Aquaculture Impacts publication trend

The graph below shows the total number of articles in tilapia lake virus pathogenesis and aquaculture impacts across all publications each year (not limited to Nature Index journals).

Technical terms

Negative‐sense RNA virus: A virus whose genome is complementary to messenger RNA and must be transcribed before protein synthesis.

Orthomyxo‐like polymerase: A multi-subunit viral enzyme that replicates and transcribes the viral RNA genome, analogous to influenza virus polymerase.

Nucleoprotein (NP): A viral protein that binds genomic RNA to form ribonucleoprotein complexes essential for replication and packaging.

Innate immunity: The non-specific, rapid defence mechanism comprising cellular and molecular responses that inhibit early virus spread.

Cryo‐electron microscopy (cryo-EM): A technique for imaging biomolecules at near‐atomic resolution by flash-freezing specimens and observing them at cryogenic temperatures.

References

1. ICTV Virus Taxonomy Profile: Amnoonviridae 2023. Journal of General Virology (2023).
2. Structural and functional analysis of the minimal orthomyxovirus-like polymerase of Tilapia Lake Virus from the highly diverged Amnoonviridae family. Nature Communications (2023).
3. Structure of the tilapia lake virus nucleoprotein bound to RNA. Nucleic Acids Research (2025).
4. Immune responses to Tilapia lake virus infection: what we know and what we don’t know. Frontiers in Immunology (2023).
5. Outbreaks of Tilapia Lake Virus Infection, Thailand, 2015–2016 - Volume 23, Number 6—June 2017 - Emerging Infectious Diseases journal - CDC. Emerging Infectious Diseases (2017).