A naturally occurring disease has been identified as the cause of death of five dolphins from Perth’s rivers and coastal waters this year.

Department of Biodiversity, Conservation and Attractions (DBCA) principal scientist Kerry Trayler said dolphin tissue samples collected by wildlife officers and tested by Murdoch University researchers have confirmed the presence of cetacean morbillivirus.

“The virus is the most significant cause of cetacean sickness and death globally with regular occurrences documented in the Mediterranean Sea and Atlantic Ocean,” Dr Trayler said.

“It spreads via infected particles breathed out of the dolphin’s blowhole, and once transmitted, the virus suppresses the animal’s immune system and damages the lungs and brain.

“Humans are not at risk from the virus, which cannot survive outside of a cetacean host.” 

Two of the five deceased dolphins were part of the Swan Canning Riverpark’s resident dolphin community.

The last outbreak of cetacean morbillivirus in the Perth region was in 2009 when six Riverpark dolphins died.

Dr Trayler said animals who survived the 2009 viral exposure would have developed natural immunity, which weakens over time, while Riverpark dolphins born after 2009 are at increased risk of infection.

“There’s still a lot we don’t know about the virus so we’re asking the public to report sightings of dolphins swimming erratically or in circles, or having difficulty breathing, or with skin and oral sores, to the Wildcare Helpline on 9474 9055.”