A researcher collects a nasal swab sample from a symptomatic elephant seal weaned pup for avian influenza testing. Photo by Frans Lanting for the Beltran Lab / UC Santa Cruz under NMFS Permit 28742
The first ever outbreak of avian influenza among elephant seals in the state has researchers on alert.
In February, seven weaned elephant seal pups in Año Nuevo State Park, just north of Santa Cruz, tested positive for highly pathogenic avian influenza (HPAI), also known as the bird flu. The outbreak marks the first case in marine mammals in California and the first detection in northern elephant seals. The disease decimated populations of a related species, southern elephant seals, in Argentina in 2023.
Currently, about 35 marine mammals are being tested for suspected influenza virus infection at Año Nuevo, but what about our rookery at Piedras Blancas in San Simeon? As of March 5, the elephant seals who breed in the area have not been affected, which is good news, but caution is still in play.
“As far as we have seen, it looks like the virus spilled over from birds to seals, but there is no evidence of seal-to-seal transmission at this point. That means it is unlikely that seals will bring the virus down from Año Nuevo” Heather E.M. Liwanag, Ph.D., a Cal Poly professor who runs the team that is monitoring the local population. told Estero Bay News. “It is possible that we could get spillover from birds to seals here, like what happened at Año Nuevo. We have been worried about that for a few years now, and the event at Año Nuevo is the first time we have seen it happen.”
Año Nuevo State Park is home to an elephant seal colony with approximately 5,000 seals during the winter breeding season. About 1,350 seals were present on the beach when the outbreak began. California State Parks has temporarily closed public access to seal viewing areas at that location and cancelled its popular guided elephant seal tours for the remainder of the season while officials investigate the wildlife health threat.
The Piedras Blancas Elephant Seal Viewing Area and Visitor Center remain open to the public. It is a popular place for locals and tourist who go to the beach to see between 4,500 and 5,000 pups born each year, which corresponds to a total population size between 20,000 and 25,000 seals. Researchers are monitoring the elephant seal population, but the avian flu is not likely to reach the local rookery.
“We have been on alert for the avian flu for a few years, since it decimated southern elephant seal populations in Argentina in 2023,” Liwanag said. “Although it is concerning to see the first jump to northern elephant seals ever, the current evidence does not indicate that we should be more concerned than we were before we saw the spillover event at Año Nuevo. Previous spillover events in the U.S., which infected harbor seals, were localized. At this time, it appears the event at Año Nuevo is also discrete.”
Should any of the elephant seals in San Simeon test positive, what would that entail?
“Right now, we are more focused on neurologic symptoms,” Barbie Halaska, a biologist with Central California Marine Animal Response Team, told Estero Bay News. “Currently, confirmed affected animals are from the Año Nuevo Reserve and contained to a small section of that state park. As it relates to Piedras Blancas, different protocols are being reviewed and adapted based on the evolving situation, as each rookery is unique. At this point, we are actively monitoring for the live symptoms and then will make updates about confirmed cases at pandemicinsights.ucdavis.edu/h5-marine-outbreak
“CCMART was able to go out and do a dead animal survey on several of the beaches by taking swabs from a couple of individuals for HPAI testing to monitor this population. At this point in time nothing is out of the ordinary.”
California State Parks says, “While risk of infection to the general public is low, HPAI can spread between animals and people. Do not touch live or dead seals or allow pets to approach them. This helps protect people and pets and also gives sick animals space”
Should readers encounter a sick, injured or dead marine mammal in California, Oregon or Washington, call the NOAA Fisheries West Coast Region Stranding Hotline: (866) 767-6114. Do not attempt to move sick wild animals, as this can spread disease and cause stress or harm to the animal.
Signs of the bird flu include “abnormal respiratory and neurological signs, including weakness and tremors,” Halaska said. “All the animals that were seen with these symptoms were found dead 24 hours later. At this point only weaned elephant seal pups are those being affected at a small, contained section of Año Nuevo Reserve.
“This age-class, weaned pups, are learning how to swim, forage on their own and adjusting to life without mom present. They are not able to swim very long or far and spend most of their time on shore near where they were birthed. Additionally, the animals that are displaying the HPAI symptoms are dying withing 24hrs.”
CCMART is a new non-profit organization that responds to dead marine mammals and sea turtles in San Luis Obispo county. They ask that if anyone come across a dead marine mammal to call at 805-242-3560 or go to their website, ccmarineresponse.org/, and fill out a dead animal report. For any live marine mammals, call the West Coast Stranding Hotline at NOAA Fisheries West Coast Region Stranding Hotline: (866) 767-6114.
While risk of infection to the general public is very low, HPAI can spread between animals and people.
“People and their pets should avoid all contact with sick or dead wildlife because HPAI can spread between animals and people (and their pets),” Halaska said. “Although the risk of infection to the general public remains low, beachgoers should not touch live or dead seals or allow pets to approach seals. They should maintain a safe distance of 150 yards or more away. And please respect closures and follow guidance at sites where special precautions are implemented.”
Since the detection of this outbreak, scientists have worked closely with the National Oceanic and Atmospheric Administration (NOAA) Fisheries, California State Parks, California Department of Fish and Wildlife, California Department of Public Health, local health officials, The Marine Mammal Center, the West Coast Marine Mammal Stranding Network, and other marine mammal researchers that monitor wild elephant seal populations.
Researchers are monitoring the situation at Año Nuevo via regular drone flights and surveys to evaluate animal health, collect samples, and screen for HPAI activity in birds and mammals.
