Could a Disease Outbreak Happen With Whales and Dolphins in Hawaii?

An infectious disease found in a stranded dolphin in Hawaii could spark an outbreak in other marine mammals, researchers say.

When investigating the 2018 death of a Fraser’s dolphin that had been stranded in Maui, researchers were concerned with what they observed. During the necropsy, they discovered a novel strain of morbillivirus, a marine mammal disease responsible for deadly outbreaks in dolphins and whales. The disease contributed to the dolphin’s death.

The findings were published in Scientific Reports.

Morbillivirus has been responsible for mass mortalities of dolphins and whales worldwide, but this was the first time it has been found in this particular species of dolphin.

The disease is related to human measles and smallpox.

“It is challenging to track a disease like this because dolphins and whales live an entirely aquatic lifestyle,” marine biologist Kristi West, director of the University of Hawaii Health and Stranding Lab, tells Treehugger.

“Our stranding response team recovers less than 5% of the carcasses from whales and dolphins that are believed to be dying at sea. This means that we are unable to examine or test the vast majority of dolphins and whales that die around the Hawaiian Islands.” 

Because of the finding, scientists are concerned about the potential of a novel morbillivirus outbreak that could spread through dolphins and whales in Hawaii.

Two strains of the virus were discovered previously in dolphins in Western Australia and in Brazil. In those mortality events, at least 50 dolphins died in Australia and more than 200 dolphins died in Brazil.

In order to determine if the disease is circulating in the Central Pacific, researchers must first perform antibody testing on marine mammals.

“Research involving antibody testing is first needed to understand if Hawaiian dolphins and whales may have acquired immunity through prior exposure to this virus,” West says.

“There is also the potential to collect exhale samples from live dolphins and whales in Hawaii for morbillivirus testing. Additionally, this finding highlights the importance of conducting comprehensive cause of death investigations on stranded animals which is the only means to determine cause of death in whales and dolphins.”   

A vaccine could help keep the disease from spreading—at least with some species.

“The world’s first marine mammal vaccination program for morbillivirus aims to reach herd immunity in endangered Hawaiian monk seals,” West says. “Monk seals are vaccinated while sleeping on the beach. A similar mass vaccination program for whales or dolphins that live an entirely aquatic lifestyle would be much more difficult.”

Potential Outbreak

Many cetacean species (whales and dolphins) may be vulnerable to the disease, which has the potential to result in mass deaths, West says.

“This is more likely when the disease spreads among a population that does not have some protection due to acquired immunity from prior exposure to the disease,” she says. “Cetacean morbillivirus can easily spread from one species of dolphin or whale to another as dolphins and whales are highly social and different species interact with each other.”

During surveys over the past two decades, Fraser’s dolphins were spotted four times with melon-headed whales and once with pilot whales. Because both these whale species interact with other species of dolphins and whales, this is a way that disease can spread from species to species, West points out.

Fraser’s dolphins are found in tropical waters around the world, but not as much is known about them as many other species of dolphins.

Their current population is unknown, according to the International Union for Conservation of Nature. They tend to be found far from shore and are highly social, traveling in groups of 10 to 100, but even in groups as large as 1,000. They also often interact with other species of dolphins and whales.