The extensive study, published in Scientific Reports, used a variety of methods to determine the presence of the virus and model its potential spread. Methods used include tracking animals using satellites, taking samples from living marine mammals and from those found dead. The analytical technique called real time PCR (polymerase chain reaction) was used to identify the virus and determine how much was present in samples taken.
The virus is known as Phocine distemper virus (PDV), usually found in the North Atlantic Ocean and can be deadly to the European Harbour seals found there. However, the new report shows “widespread exposure and infection” across the North Pacific Ocean with “peaks in exposure in 2003 and 2009”.
The transportation of this virus to the Pacific is thought to be made possible by the loss of Arctic sea ice which previously blocked the route. The data shows an open route between the Pacific and Atlantic Oceans prior to peaks in virus detection.
Scientists believe that PDV may have crossed the Arctic through a chain of different species of marine animals. These transmissions are made possible by their now overlapping habitats. PDV was even identified in northern sea otters, a sub-Artic species in the North Pacific, showing just how far the virus has spread.
The World Wildlife Fund (WWF) stated in an article on their website that “when it comes to sea ice, 95% of the oldest and thickest ice in the Arctic is already gone.”
Although no deaths have been recorded as being directly caused by PDV in the Pacific Ocean, the study notes that “the virus may have contributed to sporadic northern sea otter deaths, including those that occurred during an unusual mortality event from 2004–2006” and “to sporadic Steller sea lion deaths (PCR positive tissues in dead animals in this study).”
The health risks for this spread are unknown and although transmissions between the Pacific and Atlantic may increase in the coming years, as “open water routes between along the Russian coast have occurred every August and/or September since 2008”, nobody is certain about the long term outcome.
Read the study here.