A highly pathogenic avian influenza, or bird flu, first detected in marine mammals at Ano Nuevo State Park in California last month, is now confirmed to be present hundreds of miles south in San Luis Obispo County. The virus, a strain of HPAI H5N1, poses a growing concern for wildlife along the California coast, with confirmed cases now impacting sea lions, elephant seals, and sea otters.
The latest case, confirmed Thursday by UC Davis’ Institute for Pandemic Insights, involves a deceased California sea lion found on Morro Strand State Beach in Morro Bay. The animal, estimated to be between one and two years classic, is the third sea lion to test positive for the virus, following two earlier cases identified in San Mateo County. This marks the first documented instance of HPAI H5N1 in a marine mammal within San Luis Obispo County, according to a news release from the county’s Public Health Department.
The spread of the virus is particularly concerning given the foraging habits of juvenile sea lions. Researchers note that these animals frequently travel along the central California coast, even as far south as the Channel Islands, potentially facilitating further transmission. “Juvenile sea lions are known to forage along the central California coast traveling as far south as the primary sea lion breeding colonies on the Channel Islands,” the UC Davis release stated. “Researchers are continuing to monitor marine mammal populations all along the coast.”
Impact on Coastal Wildlife
While the initial outbreak centered on northern elephant seals, the virus has demonstrated a broadening range of affected species. At least 27 northern elephant seals have been found with the disease, resulting in the deaths of at least 47 animals, according to recent reports. Adding to the concern, at least one southern sea otter has also tested positive for HPAI H5N1. The situation highlights the vulnerability of marine mammal populations to this evolving viral threat.
The sea lion found in Morro Bay was sampled on March 16 by a researcher with the Central California Marine Animal Response Team (CCMART) and subsequently confirmed by both UC Davis and the USDA’s National Veterinary Services Laboratory on March 25. The San Luis Obispo County Public Health Department emphasized that, while the risk of transmission to humans remains low, caution is advised around potentially affected animals.
“This is especially important for animals that appear sick, injured, or deceased,” the department stated in its Friday news release. Officials urge the public not to approach marine mammals or seabirds exhibiting signs of illness and to report any sightings of sick or injured animals. The NOAA West Coast Marine Mammal Stranding Hotline (866-767-6114) and the California Department of Fish and Wildlife (916-358-2790) are available to receive reports.
Broader Regional Concerns
The emergence of avian flu in marine mammals follows earlier detections in seabirds. Earlier this month, the virus was identified in a dead common murre at Point Reyes National Seashore, marking the first such case in that area. Park staff had observed an increase in deceased seabirds beginning February 25, coinciding with the initial reports of the virus in marine mammals at Ano Nuevo State Park.
Earl Perez-Foust, a spokesperson for Point Reyes National Seashore, described the increase in bird deaths as part of “a broader regional seabird mortality event” affecting beaches throughout the Bay Area. While the reports of avian flu in marine mammals have heightened awareness, Perez-Foust noted that, as of early March, no signs of illness had been observed within the northern elephant seal colony at Point Reyes.
Public Health Response and Monitoring
Public health officials confirmed the first cases of bird flu in San Luis Obispo County in 2022. The current situation is being closely monitored by local, state, and federal agencies. The San Luis Obispo County Public Health Department encourages residents with questions to contact them directly at 805-781-5500.
The UC Davis Institute for Pandemic Insights is playing a crucial role in tracking the spread of the virus and understanding its impact on wildlife populations. Their ongoing research is essential for informing public health strategies and conservation efforts. The institute’s website provides detailed information about the outbreak and ongoing monitoring efforts.
What to Do If You See a Sick Animal
The California Department of Fish and Wildlife (CDFW) provides specific guidance for reporting sick or deceased wildlife. If you encounter a marine mammal or bird that appears ill, injured, or deceased, do not approach it. Instead, contact the appropriate authorities:
- Marine Mammals: NOAA West Coast Marine Mammal Stranding Hotline at 866-767-6114
- Birds: California Department of Fish and Wildlife at 916-358-2790
Maintaining a safe distance and reporting sightings are crucial steps in helping wildlife officials track the spread of the virus and protect vulnerable populations.
The situation remains fluid, and ongoing monitoring is critical to understanding the full extent of the outbreak and its potential consequences. The next update from the UC Davis Institute for Pandemic Insights is expected in early April, providing further insights into the virus’s progression and impact on California’s coastal ecosystems.
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