Virus found in stranded Maui dolphin puts scientists on alert
Disease could pose ‘significant threat’ to highly social species
While the human world is working tirelessly to control the impacts of the coronavirus, recent findings in the marine world are alerting scientists of a potential threat of the novel morbillivirus on Hawaii’s dolphins and whales.
After two years of investigating the cause of death of a Fraser’s dolphin that was stranded on Maui in 2018, researchers discovered a strain of morbillivirus in Hawaiian waters that “we were previously unaware of,” said Kristi West, associate researcher at the University of Hawaii at Manoa’s Hawaii Institute of Marine Biology who directs the Health and Stranding Lab.
Related to human measles and smallpox, the virus is an infectious disease responsible for deadly outbreaks among marine mammals worldwide, West said.
“We do not know where this particular dolphin came from. Fraser’s dolphins are found in offshore waters off of all of the main Hawaiian Islands, but are very infrequently sighted at sea,” West said on Friday. “In over 21 years of dedicated survey effort by Cascadia Research Collective, pods of Fraser’s dolphins have only been sighted on six occasions. We don’t know where it may have contracted the novel morbillivirus from.”
West and a team of researchers through the UH Manoa Health and Stranding Lab conducted an animal autopsy on Jan. 17, 2018, the same day that the dolphin was recovered. They published their findings last week in “Nature Scientific Reports.”
The sub-adult male dolphin that stranded at Olowalu a few years ago had morbilliviral antigen detected in the cerebrum, cerebellum, spleen, lung, kidney and lymph nodes, according to the report.
This strain is the first linked to this dolphin species.
West told The Maui News that it’s possible that the stranded dolphin was contagious and could have transmitted the virus to other small island cetacean species.
The UH Health and Stranding Lab only recovers less than 5 percent of the dolphins and whales that die in Hawaiian waters, which makes detecting disease outbreaks “very difficult.”
And sightings and strandings of Fraser’s dolphins, in particular, in Hawaii are very rare with only few reports of this species close to shore.
“Cetacean morbillivirus is believed to be transmitted by air and can easily spread among highly social dolphins and whales,” she said. “Morbillivirus can also be transmitted from one dolphin or whale species to another as different species may also be associated with each other in the wild.”
There are about 20 species of dolphins and whales that call Hawaii home “that may also be vulnerable to an outbreak from this virus,” she had said in a UH news release last week.
Because much of the information surrounding Fraser’s dolphins is still unknown, researchers say morbillivirus could be a “significant threat” to these pelagic species, which are highly social animals and interact closely with other dolphins and whales in Hawaiian waters.
The endangered insular false killer whales, of which only an estimated 167 remain, could also be at risk.
“If morbillivirus were to spread through that population, it not only poses a major hurdle to population recovery, but also could be a threat to extinction,” she added.
Two novel morbillivirus strains were previously discovered in dolphins in Western Australia and Brazil that led to unusual mortality events, with at least 50 dolphins dying in Australia and more than 200 dolphins dying in Brazil, according to the study.
There are six strains of Cetacean morbillivirus (CeMV) that have been clustered into two lineages– the CeMV-1 and the CeMV-2.
In Hawaiian waters, the strain identified in a Longman’s beaked whale that stranded in 2010 off of Maui represented the first report of CeMV-1 in the Central Pacific.
Common symptoms include pneumonia and brain infections with possible lesions seen in the lungs, mouth and skin, West said. Infected marine mammals might have abnormal behavior and the virus can spread to infect the entire body, which may also cause “immunosuppression,” which can result in death.
“Unfortunately, there is no known cure once a marine mammal is infected with morbillivirus,” she added.
Similar to the COVID-19 pandemic, further research would help to understand the vulnerability of Hawaiian species to the novel Fraser’s morbillivirus as well as implementing vaccination programs and antibody testing.
The National Oceanic and Atmospheric Administration currently has a Hawaiian monk seal morbillivirus vaccination program, which aims to reach morbillivirus herd immunity in Hawaii’s endangered monk seals.
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,” West said. “Research involving antibody testing is first needed to understand if Hawaiian dolphins and whales may have acquired immunity through prior exposure to this virus. There is also the potential to collect breath samples from live dolphins and whales in Hawaii for morbillivirus testing which could lead to a greater understanding of potential spread.”
Additionally, this finding highlights the importance of conducting “comprehensive cause of death investigations” on all stranded dolphins and whales.
Marine mammal carcass recovery rates are very low, so officials emphasize the importance of the public’s role in rapid reporting of whale and dolphin strandings.
Sightings of dead or distressed marine mammals can be reported to the toll-free statewide NOAA Marine Wildlife Hotline at (888) 256-9840.
Research through the UH Health and Stranding Lab provides hands-on opportunities for university students, said West.
“This also is anticipated to bring greater recognition to UH’s role in looking at infectious disease in Hawaiian marine mammals and how the strains found here in Hawaii compare to those that have been described in other regions of the world,” she said in the news release.
To read the full report, visit www.nature.com/articles/s41598-021-94460-6.
* Dakota Grossman can be reached at email@example.com.