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News and Resources

Virus Causing Atlantic Coast Dolphin Die Off - November 9, 2014


    Since the spring of 2013, citizens and scientists on the Atlantic Coast have noticed a disturbing trend in increasing amounts of Atlantic Bottlenose Dolphins dying compared to previous years. While not all the dolphins found are dead, some are still barely alive after being stranded, most dolphins found thus far on Atlantic Coast beaches since 2013 have died from a wide-spread and dangerous virus. 

    There are a plethora of different reasons why these Atlantic Bottlenose dolphins could be dying off in large numbers, however the biggest factor is believed to be the Morbillivirus. Other contributing factors could include other viruses, diseases or parasites, pollution and even harmful chemicals like polychlorinated biphenyls (PCBs). Biotoxins, chemicals and pollution in the water weaken the dolphins immune function and leave them more vulnerable infections and diseases and even more susceptible to die. 

    The morbillivirus is a measles-like virus which causes pneumonia and respiratory problems, skin lesions, brain and other infections, weight loss and abnormal behavior in afflicted animals and can ultimately lead to the infected animals death. The morbillivirus does not discriminate based on age or sex; it can infect males and females of all ages, regardless of health. The morbillivirus is very contagious and easily spread from dolphin to dolphin and from dolphin pod to dolphin pod. The virus can be spread through respiration, contact between infected and uninfected animals, especially skin to skin contact, and even from mother to offspring during birth and raising the calf. 

    The virus is very potent and dangerous to our dolphins; we estimate that roughly half of all dolphins that catch the morbillivirus die, meaning a roughly 50% mortality rate. Thus far in the 2013-2014 Atlantic Bottlenose dolphin die off, 95% of all dead dolphin carcasses sampled have come back positive for the morbillivirus, leading scientists to believe the virus is the main cause behind the large scale die off. Even if the dolphin is healthy enough to help fend off the virus, it can still die due to secondary infections or diseases. This happens because of the immunosuppressive impact of the morbillivirus infection, leading to increased secondary infection rates among afflicted dolphins. 

    Estimates put between 30,000 and 40,000 Atlantic Bottlenose dolphin living off the Atlantic Coast between New York and Florida. Thus far, since July 2013 along the Atlantic Coast, nearly 1,550 of these Bottlenose dolphins have died, making this one of the biggest dolphin die offs in recent history. This is not an isolated incident; nearly a quarter of a century before this 2013-2014 viral outbreak, we had another large scale dolphin die off.

     Between 1987-1988, 742 bottle nose dolphins were confirmed dead due to the morbillivirus, the first time we had seen such a large scale die off along the Atlantic Coast. The current 2013-2014 virus outbreak and subsequent die off is still underway though, with some experts expecting another two to three months more before we see dolphin strandings and death rates regress back to the normal rate, if they ever do. Scientists believe that because the last morbillivirus outbreak was over 25 years ago, most of the current Atlantic bottle nose dolphin population has limited to no immunity to the virus today, which is why we have seen such a large die off due to the virus in 2013-2014. 

    According to NOAA and other agency sources, there is little the U.S. can do currently to stop the spread of the virus or reduce mortality rates in infected dolphins along the Atlantic Coast. Some European rescue centers use a subunit vaccine to help protect their native species of dolphins from this virus, however this practice has yet to be adopted in America due to the lack of availability of the vaccine and the difficulty of successfully vaccinating the populations along the Atlantic Coast. If the morbillivirus continues to pose a threat to the populations of our dolphins, porpoises and other marine mammals, than the U.S. might reach out internationally for help in developing, creating and implanting a successful vaccine to protect our native populations. 

    The morbillivirus is not only a virus that effects dolphins, there are numerous other strands of the virus which can infect other species of terrestrial and aquatic mammals. Other strands of the virus can infect dogs and coyotes, seals and sea otters, cattle, goats and sheep, and even whales. Thankfully the dolphin specific strand of the virus cannot be transmitted to humans and there have been no cases of human illness or fatalities from the morbillivirus and this dolphin disease outbreak. That being said, dolphins are wild animals that may injure people if approached to closely, especially if the dolphin is sick, injured or unhealthy. 

    Like seals in our coastal bays, dolphins need space in order to stay safe and comfortable, so give dolphins a buffer zone between yourself and the animal so everyone can stay happy and healthy. Just like our seal steward program, if you happen to see a stranded or endangered dolphin, please report it to the Marine Animal Rescue Program (MARP) at 1-800-628-9944. The morbillivirus is a naturally occurring virus, however, when coupled with other environmental or health issues, it can pose a serious problem to individual, regional and worldwide dolphin populations. 

Harrison Jackson is the Coastal Stewards Coordinator for the Maryland Coastal Bays Program. 



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