The deadliest virus for dolphins is threatening the waters of the Mediterranean.
It is Morbillivirus, a pathogen that killed more than 1,000 dolphins in the 1990s and has once again affected the population of these cetaceans. Since 2012 a new strain of the virus has arrived from the Atlantic Ocean and has already caused a dozen strandings in Valencia and another six in Sicily.
The new variety that arrived in the Mediterranean does not spread as easily as the previous ones, so it does not produce outbreaks, but it is more deadly. Although the origin of Morbillivirus is unknown, researchers from the Oceanogràfic Foundation point to contamination as a factor that enhances its mortality.
«The pollutants in the sea cause the dolphins' immune system to weaken. That is why when the animal comes into contact with the virus it causes massive deaths», Explains Consuelo Rubio-Guerri, Research Coordinator of the Oceanogràfic Foundation. The outbreaks have taken place just when the levels of pollution in the sea were highest, so the presence of toxins is the main hypothesis of scientists. «In the Mediterranean there is a lot of movement, spills and large masses of tourists who use the beaches and cross the sea with cruise ships. Also, it is like a lake and the toxic levels are quite high"Rubio-Guerri laments.
The virus belongs to the family of measles or distemper in dogs and does not affect humans. It enters through the respiratory tract, depending on the lesions it produces in the lungs, and when it reaches the brain it is the end for the dolphins. The researcher details that «once it circulates throughout the body, it begins to produce neurological damage and causes seizures, problems when swimming and causes them to separate from the group, cannot eat and, finally, die». Some of the dolphins that arrived alive to the Valencian coast already showed symptoms and suffered seizures, so their death occurred moments after the rescue of the scientists.
This virus is just one of the threats faced by cetaceans in the Mediterranean. Overfishing has caused them to move in search of food, constantly causing conflicts between species that previously swam and hunted freely and now have to share their habitat. Furthermore, interaction with vessels, whether fishing or not, also produces strandings. Researchers have come to collect dolphins with strings on their fins, which shows - according to the coordinator - that they have been caught and then returned to the sea. Dolphins born after 2011 are not immunized and are more vulnerable to the virus.
The danger now resides in the juvenile dolphin population. Scientists argue that the oldest cetaceans have managed to become immunized against the virus by developing antibodies after the outbreaks of 1990, 2007 and 2011. Infants would also be protected by taking the mother's milk. But those born after the last epidemic occurred are the most vulnerable. His death would be a severe blow to the species because it would endanger its survival in the Mediterranean.
So far the specialists have not found a solution for the dolphins. «The vaccine is not viable because if we develop it, the really difficult thing would be to put it on animals. It is true that there are oral vaccines that have been used for wild boars, but it is much more complicated to apply this idea at sea», Highlights Rubio-Guerri. Therefore, the only alternative that the researcher values is «continue studying how the virus acts to be able to foresee if there is going to be an epidemic or to know how it will behave in the future so that we can be prepared».