Discovery of a new virus that could spread from crabs to sharks
20 August 2019
Researchers have been investigating how viruses spread between marine animals. Rhys Parry, a PhD candidate in the Asgari Lab at the University of Queensland, has identified a number of viruses which spread between marine animals, including an unexpected discovery of a virus that spreads from crabs to sharks.
Parry said, “We never thought we would be identifying the next arbovirus from a swimming crab, that is for sure. Initially, the scope of the study was to examine the incidence of flaviviruses in all eukaryotic organisms, but very quickly we realised that marine flaviviruses, specifically crustacean flaviviruses, offer some fascinating perspectives on the evolution of vector-borne flaviviruses”.
There are a number of well-known arboviruses – such as Zika, dengue and yellow fever – but there is a common misconception that these viruses are only spread by insects. In fact, arboviruses are spread by arthropods, a group which includes not only insects, but also arachnids and crustaceans.
Many arboviruses sit within the wider family of Flaviviridae, and the focus on insect-borne flaviviruses may have led to a poor understanding of the diversity and evolution of these viruses.
The research team at the University of Queensland have identified five new species of flavivirus in the ocean, three of which were found in crustaceans and two in squid. They found these novel crustacean flaviviruses to be closely related to arboviruses. Parry said, “For this study, we actually data-mined viruses from available sequencing data of wild-caught crustaceans and cephalopods. Some were hiding, unidentified, in assembled transcriptomes and we found them using related flavivirus genomes such as Zika and dengue viruses”.
In addition to this, the researchers found evidence of a flavivirus that usually infects Pacific spadenose sharks in a number of crab populations. The virus, called Wenzhou shark flavivirus, was found in gazami crab populations. Parry said, “The identification of Wenzhou shark flavivirus in the swimming crab also importantly shows that flaviviruses have gained and lost the ability to move between arthropods and vertebrates and may have moved from a marine ecosystem into terrestrial arthropods such as mosquitoes and ticks”.
It is not known if Wenzhou shark flavivirus causes disease in sharks, but according to Parry, in sharks infected with the virus, the virus is abundant throughout all tissues tested: “While we currently don't know if Wenzhou shark flavivirus causes disease, other marine flaviviruses have been found associated with disease, such as the Lumpfish flavivirus. It's important to monitor marine viruses as we currently know so little about the host-range or potential for disease”.
Their findings suggest that some ocean viruses can move between vertebrates and arthropods, potentially meaning there are ocean arboviruses yet to be discovered. Parry said, “Fragments of flaviviruses have also been recently identified in supermarket fish, so we should really be asking how extensive the host ranges of these vertebrate-infecting viruses are and how damaging these flaviviruses may be to commercial fishing”.
Parry will present his data at the Microbiology Society Focused Meeting ‘IMAV 2019: International Meeting on Arboviruses and their Vectors’. His talk titled ‘Novel flaviviruses of the ocean: Insights into the evolution and circulation of flaviviruses between marine invertebrate and vertebrate hosts,’ will take place at 14:30 on Friday 6 September. The meeting will be held at the University of Glasgow on 5–6 September.
Image: iStock/Suwatwongkham.
