Dolphins stranded on Oahu had infectious bacterial disease

University of Hawaii researchers have linked dolphin strandings this summer to a bacteria — and warn that it can potentially transfer from animals to humans.

Three striped dolphins stranded on East Oahu shorelines over seven days all tested positive for Brucella ceti, which causes flu-like symptoms.

Two were found in Waimanalo on June 7 and 8, and the third was found in Waikane on June 15, according to Kristi West, associate researcher at UH Manoa’s College of Tropical Agriculture and Human Resilience.

Scientists are urging the public to keep a safe distance from stranded animals such as the dolphins, and to immediately report any sightings to authorities.

“Brucella ceti can be dangerous to humans who touch infected marine mammals,” said West, who also directs the university’s Health and Stranding Lab. “It is best to be cautious and avoid touching or handling stranded animals.

“The study tipped us off that our striped dolphins in Hawaii are especially vulnerable to this bacterial disease,” said West. “But we’ve never had three individual striped dolphins strand in seven days, I don’t think ever, historically, in Hawaii.”

The cluster of three strandings within seven days, and within 15 miles of one another, she said, was unprecedented.

Upon examination, West said in April, there was actually another striped dolphin stranded in windward Oahu that had also tested positive for Brucella ceti.

“We’re concerned, for sure, and worried about the implications for the species,” she said. “The other thing to keep mind — to put it into context — three in seven days for us is unprecedented and very, very high, but striped dolphins are an offshore species never in less than 3,000 feet of water. They’re offshore, and so the chances of the ones that died landing on a beach is pretty low.”

So the number of dolphins impacted is likely much higher, with many more dolphins that died and were lost at sea.

The Centers for Disease Control and Prevention says brucellosis is an infectious disease caused by a family of bacteria called Brucella, which is mainly spread among animals.

While rare in the U.S., people can get brucellosis from contact with infected animals — usually livestock such as cattle, sheep and goats — or from consuming unpasteurized milk.

According to CDC, without treatment, patients can develop serious chronic disease from brucellosis. Initial symptoms include fever, sweating, headaches and fatigue. Other symptoms that may come and go including recurring fevers, arthritis and memory loss.

The Hawaii Department of Health says risk of brucellosis is low in the state. Once diagnosed, brucellosis can be treated with antibiotics.

But what concerns West is that these recent strandings may also be an indicator of a larger problem for dolphins and whales, which are sentinels of ocean health.

“We worry about other species, too,” she said.

CTAHR researchers found Brucelli ceti in other species between 2000 and 2024, including pygmy killer whales, sperm whales, spinner dolphins and a Longman’s beaked whale — but found striped dolphins to be especially vulnerable.

Many of the animals that tested positive showed severe brain and lung infections, and were at the same time infected by other viruses such as morbillivirus and herpes.

These findings were published in the May issue of “Journal of Wildlife Diseases.”

Working with the research team, UH microbiologist Michael Norris at the same time discovered a new strain of Brucella ceti in marine mammals — considered the likely cause of the recent strandings.

The work and investigation into the new strain are ongoing this summer, thanks to a grant from the U.S. Fish and Wildlife Service and Hawaii Department of Land and Natural Resources.

West says the striped dolphins infected in April and June were likely infected with this new strain, but it will take time to confirm. If confirmed, these findings will likely be published next.

Scientists are also monitoring marine mammals for signs of H5N1, or avian influenza, which has been found in bottlenose dolphins in Florida, and in sea lions and elephant seals in South America. The virus was detected among pet ducks, geese and wild birds on Oahu last year — but not in marine mammals in Hawaii.

Since many carcasses are never recovered, West encourages the public to report dead or distressed marine mammals. Reporting these sightings helps scientists track strandings and better understand what is going on in Hawaii’s oceans.

Sightings can be reported to the NOAA marine wildlife hotline at 888-256-9840.
Source: The Garden Island