Similar virus strains have led to mass die-offs of dolphins near Australia and Brazil.
Biologists in Hawaii have discovered a previously unknown strain of cetacean morbillivirus, a pathogen that can cause fatal infections in marine mammals across the ocean.
A pod of Fraser dolphins near Hawaii.
The virus was found in a Fraser dolphin—a highly social species—raising concerns that the outbreak could spread and devastate areas beyond the central Pacific.
This juvenile male Fraser dolphin stranded off the coast of Maui in 2018, initiating a two-year investigation into its health status. The dolphin’s body was in relatively good condition; however, its organs and cells showed signs of disease. A genetic analysis of cultured cells revealed the culprit to be “a new and highly distinct strain of morbillivirus” that scientists “had not known of before,” explained Krisi West, a research collaborator at the University of Hawaii Mānoa’s Hawaiʻi Institute of Marine Biology.
Only a few strains of cetacean morbillivirus are known to exist, but they all pose a threat due to causing die-offs in marine mammals, including dolphins and whales worldwide. Other species in the Morbillivirus genus include the virus that causes measles in humans and the virus that causes canine distemper.
Fraser dolphins are highly social and friendly; they are known to coexist with other dolphin and whale species. Therefore, Fraser dolphins, an oceanic species, could carry infectious pathogens to other parts of the world. This compels wildlife managers and conservationists to prepare for potential outbreaks.
The infected Fraser dolphin before the necropsy.
“This is very important for Hawaii because we have many other dolphin and whale species—about 20 species consider Hawaiʻi home—that could easily be susceptible to outbreaks caused by this virus. One example is the island’s monk seal species, which is estimated to have only 167 individuals left. If morbillivirus spreads through that population, it would not only pose a significant barrier to population recovery but could also threaten extinction,” West added.
Indeed, this is a very serious issue. Two previous incidents involving new strains of morbillivirus have led to high mortality rates in dolphins off the coast of Brazil and western Australia. In the Brazilian case, over 200 Guiana dolphins were reported to have died from this disease between November and December 2017.
The study’s authors state that further research is needed to assess the immunity rates of dolphins and whales in the central Pacific, as this could help determine previous infection rates and the extent of outbreaks. However, addressing this disease will not be easy; the UH Health and Stranding Lab has recovered less than 5% of dead whale specimens in Hawaiian waters.
There is hope for a mass vaccination campaign. As the press release indicates, NOAA is implementing a vaccination program against morbillivirus to establish herd immunity among the endangered Hawaiian monk seals. Additionally, oceanic dolphins are also poised for vaccination.
