By Amanda Bates
We live in a time when our climate is warming more rapidly than ever before. Rising temperature and associated changes in weather are driving shifts in the distributions of species on Earth. Some are thriving in these new climate conditions and have even moved into new regions that were historically inhospitable. One concern for us humans is how harmful species – diseases or pests – are responding to a changing climate.
An example is the malaria parasite, which is transmitted to humans by tropical mosquitos. In the western highlands of Colombia, malaria is slowly creeping upwards in elevation as the climate warms. But these diseases don’t just directly harm humans. Some species of wildlife are being infected by diseases that are thriving in a warmer climate? Should we be concerned?
In the spring of 2008 I first started noticing that large ochre sea stars (or starfish) known as Pisaster were literally turning to ooze on the western coast of Vancouver Island – both on beaches and in experimental aquariums.
It was a gruesome sight. Symptoms of wasting started with lesions or bulging of the tissues, and in some cases, the arms even dropped off. I tried anti-fungal and bacteria agents, and even tea tree oil, yet the only way that I found to control the disease was to move infected animals to cooler temperatures.
What struck me at the time was how rapidly wasting spread among my animals, with death the ultimate outcome, all in the span of few days. In particular, I found that outbreaks occurred when animals were exposed to temperatures that were warmer than they were used to.
In a scientific study where I reported these results with my collaborators, I suggested that this “sea star wasting disease” could be triggered by changing climate conditions and even lead to large-scale outbreaks.
A virus is the likely culprit
Starting in early summer of 2013 starfish starting dying in massive numbers. Dozens of sea star species were affected and millions of individuals were wiped out along the entire Pacific coast of North America – an exceptional event that captured international media attention and puzzled scientists.
A new study published in the Proceedings of the National Academy of Science has exposed the culprit. The authors present compelling evidence that a virus (Parvoviridae) is responsible for the wasting disease – they were able to infect healthy sea stars with the virus, which then leads to wasting symptoms. They also found that the virus is common in the sea star’s environment, and is even associated with urchins, distant cousins of sea stars. But perhaps more intriguing, the authors identify the virus in museum specimens dating back to 1942. More....