Plate Nº 54 · recorded November 11, 2026
Biology & EvolutionReported finding
Eel Bites Spread Herpesvirus, Study Finds — Upending Fish Virology
One bite transmitted a herpesvirus to every exposed eel in lab tests, University of Liège researchers report — upending ideas about how fish viruses spread.
By Nathan Brooks4 min read704 words
In brief
- In all three experimental biting scenarios, 100% of exposed eels became infected with AngHV-1.
- The virus loses about 90% of its infectivity in water after 12 hours under the studied conditions.
- Young eels reaching European coasts today are at roughly 1% of early-1980s levels.
- AngHV-1 mortality can reach 30% in intensive aquaculture facilities.
- The study, first-authored by Natacha Delrez, was published in the Journal of Virology (2026).
A single bite between eels was enough to transmit a deadly herpesvirus, and in three experimental scenarios, every exposed eel became infected. That's the headline finding from a University of Liège team published in the Journal of Virology, and it overturns a long-standing assumption about how fish viruses move through the world.
Until now, aquatic virology's working model held that fish viruses spread mainly through water, which carries viral particles from infected animals to healthy ones. The Liège researchers, led by Professor Alain Vanderplasschen of the Laboratory of Virology and Vaccinology, showed there's a second route — and it's remarkably efficient.
Why does this matter for a critically endangered fish?
The virus in question, AngHV-1, attacks the European eel (Anguilla anguilla), a species the IUCN classifies as critically endangered. Young eels arriving on European coasts today represent only about 1% of the levels estimated in the early 1980s — a collapse of roughly 99% over four decades.
Migration barriers, pollution, overfishing and climate change all drive that decline. Infectious disease adds pressure on top. AngHV-1 causes hemorrhagic lesions — bleeding sores — on the skin and gills, and mortality can reach 30% in intensive aquaculture facilities. That's nearly one in three fish in the worst-hit farms.
The puzzle Vanderplasschen's team set out to solve was straightforward: how does the virus keep circulating in wild populations where eels live relatively far apart?
What did the biting experiments show?
Eels can be aggressive toward their own kind, biting each other around the mouth or on the tail. The researchers experimentally reproduced several epidemiological scenarios involving bites between infected and uninfected eels. In all three scenarios examined, every exposed animal developed an infection.
One such contact, the experiments demonstrate, can be sufficient to transmit the virus. The findings suggest that social interactions — even antagonistic ones — can play a decisive role in viral spread in aquatic environments.
The study also hints at why biting works so well. Under the conditions studied, the virus loses roughly 90% of its infectivity in water after just 12 hours. The mucus coating an eel's skin can neutralize the virus too. Biting lets the virus bypass both obstacles, passing directly from fish to fish without needing to survive in the environment.
That mechanism could explain how infection persists even in low-density eel populations.
How do you track a virus inside a living eel?
The team used in vivo bioluminescence imaging — essentially, making the virus glow. They genetically modified AngHV-1 to express a firefly enzyme, so the virus produces light as it replicates in infected tissues. The glow is invisible to the naked eye but detectable with specialized equipment, letting researchers follow the infection's progression inside the animal's body.
This technique yielded a second discovery: susceptibility to the virus depends strongly on developmental stage. Glass eels — the still-translucent juveniles arriving on European coasts — resisted infection when exposed through water immersion. Yellow eels, the older stage that lives and grows in inland waters, were particularly susceptible. The gills and the mucous membranes of the mouth serve as the virus's main entry points.
The researchers also noticed that infected eels kept in groups developed more infection sites on their skin than isolated ones. That difference helped confirm biting's role in transmission.
Who did the work, and what comes next?
Natacha Delrez is first author of the publication, working alongside Mathieu Denoël, Michael Ovidio and Billy Nzau Matondo. The project brought together several University of Liège teams spanning veterinary virology, ecology, species conservation, aquatic resource management and aquaculture, with contributions from the University of Mons and the University of Glasgow.
The full paper — "Illumination of anguillid herpesvirus 1 transmission in European eels reveals the importance of host developmental stage and agonistic social interactions" — carries a 2026 publication date (DOI: 10.1128/jvi.00831-26).
The findings are preliminary in the sense that they come from experimental conditions, not direct observation of wild transmission. Still, the implications reach beyond one species. The authors argue the results call for a reassessment of how viruses spread among fish generally, and could sharpen disease prevention in aquaculture as well as conservation and restocking programs for wild populations.
via phys.org/rss-feed/ (Source)
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