Francisca Samsing, Phoebe Arbon, Matthew Arnold, Andrew C. Barnes, David Bass, Joy A. Becker, Jerusha Bennett, Charles Caraguel, Jeremy Carson, Vincenzo A. Costa, Thomas Dumond, Jemma Geoghegan, Kate S. Hutson, Garry Knowles, Jasmine Knowles, Katherine Lockton, Matthew Pope, Oleksandra Rudenko, Roisin Sullivan, Felix Zareie-Vaux, Jane Williams, Kerrie Wiley
The current generation of sequencing technologies can produce terabases of data with exceptional accuracy and speed, at a fraction of the cost of older methods. Despite this unprecedented power, adoption into aquaculture health management presents several challenges, including identifying where such capability may be optimally deployed. Here we synthesise discussions from a structured expert workshop held at the 2025 Aotearoa Aquatic Diseases Symposium in Dunedin, New Zealand, where experts from industry, government and academia explored the challenges and opportunities for adopting high-throughput sequencing (HTS) to support disease investigations in aquaculture. Workshop participants identified key applications for HTS, including pathogen discovery during unexplained mortality events and source attribution in epidemics, but also noted technical, regulatory and social challenges for widespread adoption. These include the need for standardised sampling and bioinformatic workflows, data sovereignty, equitable access to the technology and uncertainty around interpreting detection of notifiable pathogens. Targeted research and coordinated regulatory frameworks will be essential to guide responsible use of HTS and determine where it adds value relative to existing approaches. Clarifying these opportunities and constraints will guide the responsible adoption of HTS into aquaculture health management to support sustainable growth for the sector.
Rowan Durrant, Jonathan Dushoff, Matthew Arnold, Christina Cobbold, Katie Hampson
Viral genes sometimes use certain codons more than others due to their nucleotide content, translational efficiency, and selection pressure from the host immune system. The rabies virus (RABV) is a negative strand RNA virus which can infect a broad range of mammalian hosts, with many of its clades circulating predominantly in specific host species. Previous work on codon usage in RABV has focused only on broader viral clades. We use publicly available RABV nucleoprotein gene sequences to investigate how dinucleotide content and codon usage biases differ between host-associated clades, and what drives these differences. We found that codon usage varies most between bat- and carnivore-associated RABV clades, and more subtly between host-species-specific minor clades within these groups. C1, GA3, and GT3 content were found to have a strong influence over codon usage patterns, and cytosine-guanine dinucleotide (CpG) content was higher in carnivore-associated RABV clades than in bat-associated clades. This, along with lower numbers of zinc-finger antiviral protein binding motifs than would be expected based on (di)nucleotide composition in bat-associated RABV sequences, suggests that bat-associated RABV clades may be under higher selection pressure from the host’s zinc-finger antiviral protein than carnivore-associated clades are, warranting further investigation of the mechanism underpinning this change.
Matthew J. Arnold, Laura M. Bergner, Haris Malik, Nardus Mollentze, Daniel G. Streicker, and Simon A. Babayan
Knowledge of viral infection in marine mammals, a group severely threatened by human activity, is largely limited to the pathology and epidemiology of few endemic viruses. The recent emergence in marine mammals of high-consequence viruses, such as H5N1 avian influenza and rabies, underscores the importance of understanding the ecology of viral transmission in these species. Metatranscriptomic approaches now enable relatively unbiased characterization of full viral communities that can reveal ecological and evolutionary drivers of infection. We sequenced RNA from 15 marine mammal species (42 pools, 237 tissues,128 animals) sampled in Scotland through the Scottish Marine Animal Strandings Scheme. Viral sequences were detected in 41 of 42 pools, representing more than 120 distinct viral taxonomic units (vOTUs). Virus host network analysis showed that viral communities were partly structured by host taxonomy, with clear differences between seals and cetaceans. However, vOTUs were frequently shared between species, mirroring reported ecological interactions, including cross-order sharing between seals and cetaceans. Generalised linear models showed no effect of host taxonomy on viral richness. Instead, age was the strongest predictor: juvenile pools contained roughly twice as many viral taxa as adults and more than neonates, indicating that changing population demography may impact viral transmission in marine mammals. These results provide a basis for understanding how anthropogenic stressors may exacerbate viral transmission in marine mammals and demonstrate the increasing practicality of using genomics to understand ecological and evolutionary drivers of virus infection in natural populations.
Rommel J Gestuveo, Rhys Parry, Laura B Dickson, Sebastian Lequime, Vattipally B Sreenu, Matthew J Arnold, Alexander A Khromykh, Esther Schnettler, Louis Lambrechts, Margus Varjak, Alain Kohl
Aedes aegypti mosquitoes that transmit human-pathogenic viruses rely on the exogenous small interfering RNA (exo-siRNA) pathway as part of antiviral responses. This pathway is triggered by virus-derived double-stranded RNA (dsRNA) produced during viral replication that is then cleaved by Dicer 2 (Dcr2) into virus-derived small interfering RNAs (vsiRNAs). These vsiRNAs target viral RNA, leading to suppression of viral replication. The importance of Dcr2 in this pathway has been intensely studied in the Drosophila melanogaster model but is largely lacking in mosquitoes. Here, we have identified conserved and functionally relevant amino acids in the helicase and RNase III domains of Ae. aegypti Dcr2 that are important in its silencing activity and antiviral responses against Semliki Forest virus (SFV). Small RNA sequencing of SFV-infected mosquito cells with functional or mutated Dcr2 gave new insights into the nature and origin of vsiRNAs. The findings of this study, together with the different molecular tools we have previously developed to investigate the exo-siRNA pathway of mosquito cells, have started to uncover important properties of Dcr2 that could be valuable in understanding mosquito-arbovirus interactions and potentially in developing or assisting vector control strategies.