Since 2013, billions of Seesternen have died of an unknown infectious disease. This epidemic also has serious consequences for other sea creatures. Now biologists have identified the pathogen of this mysterious disease. Accordingly, it is a tribe of the species of bacteria Vibrio Pectenicida. With the knowledge, the infection and treatments can now be searched for, so that the microbes will be fought in the future and the affected coastal ecosystems can recover from the disease.
In 2013, a new illness occurred at Seesternen. The marine animals are exhausted by the infection, its fabric melts formally and disintegrates within two weeks, so it is called “Sea Earth Disease Disease” (SSWD). At least 20 of the more than 1900 naval species worldwide are affected. The disease is rampant primarily in populations along the Pacific coast of North America, from Mexico to Alaska. The unknown pathogens have already fallen victim to billions of seafares.
This epidemic has brought the marine ecosystems out of balance in the Pacific. Because without the predatory naval stars, their preferred prey could spread quickly: the sea urchins. These feed on seaweed forests, eat bare and in turn rob thousands of other marine residents their habitat. This has consequences for fishing. In addition, the seaweed forests are then missing as a natural CO2 memory and for coastal protection. “This has far -reaching effects on all other types of sea and the people who are dependent on the seaweed. The loss of a naval native goes far beyond the loss of this individual kind,” says Melanie Prentice from the University of British Columbia in Vancouver.
The trigger is a bacterial base
After years of search, the team around Prentice has now identified the pathogens. For this purpose, the biologists carried out various experiments with wild and bred sunflower seas esters (Pycnopodia helianthoides). This species has 24 arms and becomes as big as a bicycle tire. It is now threatened with extinction by the SSWD epidemic. In the tests, Prentice and their colleagues set out the Seesterne trials with contaminated tissue or body fluid from sick individuals. Then they examined the tissue of the naval esters and their blood-like body fluid and compared the DNA in the samples with those of healthy control seas eaters. From this they concluded which types of microorganisms live on the healthy and sick.
The evaluation showed that the pathogen of the naval disease is not as previously suspected a virus, but a bacterium called Vibrio Pectenicida. This bacterium is one of the same genus as the pathogen of the cholera (vibrio cholerae) and vibrio species in the sea such as Vibrio Parahaemolyticus and Vibrio Vulnificus, which can trigger breaks and make fish sick. The FHCF-3 trunk, which is now identified in the Seestern, is also closely related to another bacterial base of V. Pectenicida, which infects the larvae of scallops and oysters and kills them with a special poison that inhibits the immune system of the mussels. Follow-up experiments with targeted infections with the newly identified bacterial strain FHCF-3 confirmed the finding: the seafares sufferers and died from this new way.
End of the epidemic in sight?
With the knowledge of the pathogen, the naval disease can now be researched in more detail. Among other things, the marine biologists want to find out which types of naval species and populations are affected by the bacterium, whether the bacterial base also kills over a poison and in which way the infection takes place. Because it is still unclear whether the Seesterne is infected by their peers or through food, such as infected molluscs. In addition, Prentice and her colleagues want to investigate the first indications that the pathogen spreads particularly in warm sea water, for example during marine heat waves.
From this, new treatments can be developed in order to contain the epidemic and avoid new outbreaks. For example, fjords with cold water could serve as a naval priority or probiotics. The team hopes that the affected seaweed forests and their coastal ecosystems could one day recover from the disease.
Source: Melanie Prentice (University of British Columbia) et al.; Nature Ecology & Evolution, DOI: 10.1038/S41559-02797-2
