A series of great white shark deaths along the Atlantic coast of North America has been linked to brain inflammation.
Brain tissue from a stranded shark has been sent to the Washington Animal Disease Diagnostic Laboratory for genetic sequencing, which may reveal the virus or bacteria behind the meningoencephalitis. (Illustration: Peter Symes / AI)
Marine biologists are investigating unexplained deaths among great white sharks along the Atlantic coastline of the United States and Canada. Since 2022, at least nine carcasses have washed ashore, with necropsies revealing a common factor: meningoencephalitis, an inflammation of the brain and its surrounding tissues.
Findings and implications
The first documented case occurred in August 2023, when a great white shark was found on a beach in Prince Edward Island, Canada, showing no external injuries. Subsequent microscopic examinations identified meningoencephalitis as the cause of death. This condition can impair cognitive functions, disrupting essential behaviours such as swimming and hunting. But meningoencephalitis is a symptom, not a disease – and what caused the inflammation, experts do not know.
In an email to IFLScience, Dr Harley Newton, Chief Scientist and Veterinarian at OCEARCH, noted the rarity of such findings:
"While having multiple sharks of the same size/age class/species strand with signs of brain inflammation in clusters over a few years is concerning, it is hard to say how much concern there should be as we do not understand how this fits into the greater picture of wild shark health."
The underlying cause of the meningoencephalitis remains unidentified. Researchers are exploring various possibilities, including bacterial, viral, or environmental factors, but no definitive conclusions have been reached.
Broader context
This phenomenon is not isolated to great white sharks. In March 2022, a Greenland shark stranded on a beach in Cornwall, England, was found to have died from meningitis, marking the first recorded case of a disease-related death in this species.
Additionally, juvenile salmon sharks along the Pacific coast of California have been documented with meningoencephalitis associated with Carnobacterium maltaromaticum-like bacteria, suggesting that brain infections may be a broader concern among shark species.
Ongoing research and conservation
Understanding the prevalence and causes of meningoencephalitis in sharks is crucial for conservation efforts, especially given the ecological importance of these apex predators. Researchers continue monitoring shark populations and conducting necropsies on stranded individuals to gather more data.
