Two endangered Hawaiian monk seal pups are responding well after receiving vaccinations against a highly contagious strain of avian influenza.
The seal pups have been in the care of the veterinary team at Ke Kai Ola, the Marine Mammal Center's dedicated hospital for Hawaiian monk seals in Kona.
Dr. Sophie Whoriskey, the hospital's associate director of conservation medicine, said the pups haven't experienced any negative side effects from the vaccine.
This trial at Ke Kai Ola could be the first step in a larger vaccination campaign to protect Hawaiʻi's endangered monk seals from avian flu, which has decimated other marine mammal populations.
While avian flu mainly circulates among wild birds and poultry, a widespread H5N1 strain is particularly adept at jumping between species, including marine mammals like dolphins, seals, and sea lions.
Bird flu outbreaks have decimated Argentina's remote population of Southern elephant seals, which have limited immunity to the virus. Thousands of seals and pups have died, and it may take up to a century for their population to recover.
Dr. Whoriskey said there's concern that the same thing could happen to Hawaiʻi's endangered monk seals if they are exposed to the virus.
"Our worst-case scenario is that it would cause a catastrophic outbreak and potentially drop the population below recoverable levels," she said.
The risk of bird flu in Hawaiʻi
The state confirmed one case of bird flu in a migratory pintail duck found on the University of Hawaiʻi at Mānoa campus on Oʻahu in October. A second case was detected in another migratory duck on Maui in November.
Dr. Thierry Work, a USGS wildlife disease specialist based in Honolulu, said that since these cases have been isolated and in migratory species, there may not be community spread of H5N1 in Hawaiʻi's wild bird populations.
"Given that we know there's a lot of activity in North America right now, it's not terribly surprising that we get the occasional vagrant bird that comes in Hawaiʻi that pops up positive with [avian influenza]," he said.
However, a recent presumptive positive case in a native duck on Kauaʻi may change that picture.
Local disease experts are waiting on lab results to determine what killed a koloa maoli found at the Hanalei National Wildlife Refuge in late November. If it turns out to be positive for H5N1, it will be Hawaiʻi’s first case of avian flu in a native bird.
"There's always a concern that if it got established here and we had community spread, that could potentially be a big problem with our endangered birds," Work said.
It would also put Hawaiian monk seals at greater risk.
There are about 1,600 Hawaiian monk seals, and they primarily inhabit the Northwestern Hawaiian Islands, often in close proximity to seabird colonies.
"Those islands are a lot smaller and there's a lot more crossover, so the potential there for transmission is quite high," Whoriskey said.
Whoriskey and her colleagues are keeping a close eye on local bird flu cases, as Hawaiʻi's overall risk level will be an important factor in the decision on whether or not to vaccinate more monk seals.
The decision to launch such a vaccine campaign ultimately falls with NOAA, but Ke Kai Ola’'s trial will be key in determining whether such vaccines would be effective.
The two monk seal pups are being monitored to see if their immune systems mount an antibody response against H5N1, which would indicate that the vaccine is working.
This H5N1 vaccine was initially formulated and licensed for cattle, but Whoriskey said there is strong data support that it is safe to use in monk seals. Prior to this local trial, the vaccine was administered to elephant seals in California, and it has also been tested in other seals and sea lions.
"Everything we do in wildlife medicine is often what we call off-label. We have to extrapolate from things that have been designed for a different species to then use in another," Whoriskey said.
While vaccines are a promising tool to protect Hawaiian monk seals from avian flu, Work said it's not a realistic treatment for other animals, like local waterfowl species.
"Vaccination ideally works best in animal populations that are well-defined and accessible, where you can deliver the vaccine in a safe and efficacious manner," he said. "And I think for wild bird populations, that's a really difficult proposition."
