Over the course of just four days, between the 19th and 22nd of February 2014, the Oregon Marine Mammal Stranding Network was alerted to strandings of four striped dolphins (Stenella coeruleoalba) and one Dall's porpoise (Phocoenoides dalli), along a 174 mile stretch of the Oregon coast between Gearhart and North Bend. Necropsies were performed on 4 of the 5 animals by Jim Rice and Debbie Duffield (of Portland State University). One of the dolphins had stranded alive alongside a conspecific that died on the beach and was pushed back into the water by passers-by and was never reported again. All of the animals that were examined appeared to have succumbed to acute neurological disorders.
Histopathology of harvested tissues was performed by the Veterinary Diagnostic Laboratory at Oregon State University. All three dolphins were found to have severe meningitis and encephalitis (acute inflammation of the brain). Brucella sp. was later isolated by from brain tissue by the National Veterinary Services Laboratories (Ames, IA). Brucella is a bacterial agent that causes brucellosis, an infectious and zoonotic (transmissible between humans and animals) disease.
The fifth animal was an adult male Dall’s porpoise which stranded alive on a remote beach north of North Bend. People on the beach had tried unsuccessfully to re-float it for several hours before it was eventually euthanized by Jim Rice. Pathology results also indicated brain lesions, however in this case they were not caused by brucellosis but by protozoan parasites.
Although it’s highly unusual to have so many cetaceans strand within such a short period of time, it’s worth noting that 5 dolphins also stranded on Oregon beaches within the period of a week in December of 2012. Most of those animals were also found to have been debilitated by brain lesions caused by brucellosis.
Jim Rice and Debbie Duffield of Portland State University conduct a necropsy on a striped dolphin that came ashore near Florence. (Photo by Nancy Steinberg)