Bird flu found in seals: La Jolla seal colony not affected
By Lynne Friedmann
Last fall, 162 dead harbor seal pups washed up on the shores of New England. A team of researchers immediately went to work seeking a cause. In the process they identified a new strain of influenza that has “jumped” from birds to the marine mammals with the ability to spread from seal to seal. The findings appear in the July/August issue of the journal mBio (http://bit.ly/M9Bqb6).
The discovery begs the question: Is there an immediate risk to harbor seals in the La Jolla Children’s pool and, subsequently, to the public?
The short answer is: No.
To date, influenza has not been detected in the La Jolla seals. This according to SeaWorld San Diego, which regularly screens ill, injured, or stranded harbor seals rescued near the Children’s pool as part of the park’s marine mammal stranding program. Screening is done through blood, fecal, and urine tests, X-rays, and physicals exams to get a sense of any potential health problems.
Monitoring is ongoing.
That being said, vigilance is called for.
“Just as with the seals in New England, all seal populations could potentially contract the influenza virus,” said Judy A. St. Leger, DVM, DACVP, SeaWorld Parks & Entertainments corporate director of pathology and research, and an author on the study.
This is not the first time that fatal influenza has been observed in seal populations. Starting in 1979, there have been a handful of outbreaks caused by different flu strains that have affected seals. In the most recent case, post-mortem (necropsy) analysis of five seal pups pointed convincingly to avian H3N8 influenza A virus; similar to a virus circulating in North American waterfowl since at least 2002.
The work, carried out by the Center for Infection & Immunity at Columbia University’s Mailman School of Public Health, the National Oceanic and Atmospheric Administration (NOAA), New England Aquarium, the USGS National Wildlife Health Center, SeaWorld, and EcoHealth Alliance, reflects the collaborative efforts of biologists and researchers from agencies, organizations, and the zoological park industry around the globe to assist in the rescue of stranded marine mammals and to investigate the underlying causes.
Ducks and geese carry a wide range of flu strains sometimes infecting individual mammals, but rarely does the virus spread from one mammal to another. Mutations of the H3N8 virus, however, indicate recent adaption to mammal hosts with the potential for cross-species transmission.
Should cross-species transmission occur, infected seals could then act as a source for human infection. Thus, the new virus, dubbed “seal H3N8,” is being studied to see if it poses a threat for human health, bearing in mind that the discovery a new mammal-mediated virus does not mean a human pandemic is inevitable.
NOTE: Seal H3N8 should not be confused with avian H5N1, the most worrisome subtype of bird flu virus to date, which has spread across Asia and Africa. Since 2003, there have been 607 cases of H5N1 in humans worldwide, leading to 358 deaths.
While more information about seal H3N8 is being uncovered, a monitoring system is already solidly in place with NOAA’s National Marine Fisheries Service as the lead agency that coordinates responses and investigations of marine mammal mortality events.
“The marine mammal stranding network, which is composed of scientific, academic, rehabilitation, and state and Federal agencies, would notify the Working Group on Marine Mammal Unusual Mortality Events if they suspected that there was a significant die-off of harbor seals along our coast,” said Kerri Danil, research biologist with NOAA’s Southwest Fisheries Science Center, in La Jolla. “The Working Group reviews all available information and determines if a mortality event is unusual by using standardized criteria.”
An Unusual Mortality Event (UME) is defined under the Marine Mammal Protection Act as a stranding that is unexpected, involves a significant die-off of any marine mammal population, and demands immediate response. There are seven criteria used to determine whether a mortality event is “unusual.”
A single criterion or combination of criteria may indicate the occurrence of an unusual mortality event. In the case of the 2011 die-off of harbor seal pups, four of the seven UME criteria were present.
Once a UME is declared, the Working Group provides advice on investigations and funding for investigations. In San Diego, SeaWorld and NOAA’s Southwest Fisheries Science Center are the local stranding responders and would lead any local investigations pertaining to such an event.
Further information on Unusual Mortality Events, the Working Group, and criteria used to determine occurrence of a UME can be found at:
Lynne Friedmann is a science writer based in Solana Beach.
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