From New York State to North Carolina 357 dead or dying bottlenose dolphins have washed ashore since July 1st, the largest number of deaths in a quarter century. The National Oceanic and Atmospheric Administration (NOAA) has declared the die offs to be an unusual mortality event and released funds for an investigation.
NOAA says the likely culprit is cetacean morbillivirus, which is spreading throughout the population. The RNA virus is related to measles and has been confirmed in 32-33 dolphins tested so far. Scientists have no treatment for infected dolphins. The virus poses no threat to humans, but secondary infections could be dangerous.
In the past, dolphins apparently built up a level of antibody defense against the virus so it did not always lead to death. This led to lower mortality rates. Scientist do not understand why the disease is so lethal this year. Other factors being looked at by marine scientists include high levels of PCP and other chemicals in the water. Also, secondary infections by fungi, bacteria and parasites have been noted. Some researchers are wondering if poor environmental conditions fueled by agricultural runoff and other human activities made dolphins unable to weather the disease.
In Florida, Dolphin die offs are going on in three different places and appear to be from more than one cause. In addition to the morbillivirus some dolphins have died from a bacterial infection called Brucella, which scientists believe resulted from oil from the Deepwater Horizon oil spill suppressing the dolphins’ immune system. Lastly, dolphins began dying in droves beginning last year in the Indian River Lagoon on Florida’s east coast. Scientists believe it has something to do with the massive blooms of toxic algae that wiped out nearly half of the lagoon’s sea grass beds.
It is important that scientists track their deaths and identify their causes because dolphins help serve as a barometer of ocean and human health.