From land to sea to sea otter
Aparasite known only to be hosted in North America by the Virginia opossum is infecting sea otters along the West Coast. Sea otters ranging from Southern California to Alaska were tested for the presence of Sarcocystis neurona, a parasite and important cause of death in the marine mammals.
Several infected sea otters were found in the northern part of Vancouver Island in British Columbia, where Virginia opossums are not known to live.
“We were pretty sure it comes from the land, but we didn’t really know how this pathogen finds them,” says lead author Tristan Burgess. Results suggest the pathogen may be carried by water runoff from land to sea, where it can be concentrated through ocean movement and prey species, such as clams.
Most infections occurred in California and Washington, more so than Alaska and British Columbia. Higher risks of exposure were associated with habitats of soft sediment such as the mouths of rivers and estuaries and otters consuming a diet rich in clams. Humandense habitats, some wetlands and croplands were also a factor – although wetlands can help filter and deactivate some pathogens, the study noted they may be potential opossum habitat.
“We should remember the value of marine mammals as sentinels, not just of the health of their marine habitat, but of nearby terrestrial environments, too,” states Burgess. Jo Price
FIND OUT MORE
Scientific Reports: go.nature.com/2wUV0aj