What’s Been Killing Dolphins? A Measles-Like Virus, Most Likely

It has not been a good summer to be a dolphin. Over the last couple of months, more than 300 have washed on shore, dead on arrival—that’s more than 10-times the normal rate. It’s been 25 years since scientists have seen anything like this in dolphin populations off the East Coast of the United States, and they’ve been frantically looking for answers.

This week, they announced they may have found one. Here’s Nadia Drake, writing for Wired:

Now, a NOAA team in charge of investigating the event is pointing to a type of morbillivirus as the culprit behind the bottlenose dolphins deaths. Morbilliviruses are responsible for measles in humans, rinderpest in cattle, and canine distemper in dogs, coyotes, wolves and seals. There is no easy way to identify morbillivirus infection just by looking at a carcass, so identifying the pathogen as the cause of the die-off involved a feat of molecular detective work using tissue collected from the dead animals.

Getting to the bottom of the mass die-off was not easy. Scientists had to get to the carcasses quickly enough to take viable samples. If a dead dolphin sat on the beach for too long, it was difficult if not impossible to judge whether morbillivirus was the cause.

Bottlenose dolphins have been dying at an alarming rate off the U.S. East Coast

Now that the cause of the mortality event has, for the most part, been nailed down, scientists have to sit, wait, and hope. There’s no way to immunize dolphins against the virus. Fortunately, not all bottlenose dolphins will die from the illness, ensuring future populations have enough antibodies against the disease. That should tamp down future outbreaks, making them less severe—at least until a few decades from now, when immunity acquired from this outbreak is lost.