The deadliest known outbreak of a measles-like virus in bottlenose dolphins has killed a record number of the animals along the US Atlantic coast since July, officials said on Friday.
A total of 753 bottlenose dolphins have washed up from New York to Florida from July 1 until Sunday last week, the National Oceanic and Atmospheric Administration (NOAA) said.
That is more than 10 times the number of dolphins that would typically turn up dead along East Coast beaches, NOAA Fisheries Marine Mammal Health and Stranding Response Program coordinator Teri Rowles said.
“Historic averages for this same time frame, same geographic area is only 74, so you get an idea of the scope,” she told reporters.
The death toll is also higher than the more than 740 strandings in the last major Atlantic morbillivirus outbreak in 1987 to 1988.
And they have come in a much shorter time period, leading officials to anticipate this event could get much worse.
“It is expected that the confirmed mortalities will be higher,” Rowles said.
“If this plays out similar to the ‘87 to ‘88 die-off, we are less than halfway through that time frame,” she said.
The cause of death is morbillivirus, a form of measles that is similar to canine distemper and can cause pneumonia, suppressed immune function and usually fatal brain infections.
There is no evidence that cetacean morbillivirus can cause disease in people.
However, sick dolphins can also have bacterial or fungal infections that do pose risks to people, so beachcombers are advised not to approach stranded animals, but rather to call a local stranding network for help. The virus spreads among dolphins in close contact.
A handful of washed up humpback whales and pygmy sperm whales have also tested positive for morbillivirus, but scientists have not been able to confirm that morbillivirus was the cause of those deaths since the animals were too decomposed by the time tests could be done.
Among bottlenose dolphins, immunity to the virus has been decreasing, particularly in the younger animals as time has gone by since the last outbreak 25 years ago.
“So we know we had a susceptible population, but just being susceptible alone is not how the outbreaks go,” she said. “We are trying to understand where this virus came from and how it got into the population in which it is now circulating.”
Recent tests on three other species that have been found stranded — spotted dolphins, harp seals and common dolphins — have all been negative for morbillivirus.
Without a way to vaccinate the wild population, there is little that officials can do, but collect the carcasses and continue to study them.