A morbillivirus is putting dolphins through hoops!

In 1990, a morbillivirus epidemic began in the seas off Spain, before spreading to the French Mediterranean coast. In all, 160 dead striped dolphins and white whales were found on French beaches. Altogether, more than a thousand were found around the Mediterranean. In the summer of 2007, the epidemic recurred, infecting more than 126 cetaceans, this time including the species known as bottlenose dolphins.

Marine mammal beachings along the French coast have been recorded by scientists since 1972. According to Nicolas Keck, a veterinary surgeon with the Herault Departmental Laboratory, 'beached dolphins are regularly found along the Mediterranean coast, for various reasons, primarily due to accidents and infections. The death rate is occasionally higher, generally as a result of the morbillivirus.'

As Genevieve Libeau, a CIRAD researcher, explains: 'dolphins are susceptible to the morbillivirus and develop the disease. Their high density in the Mediterranean and their gregariousness favour the spread of the morbillivirus. We have observed epidemic peaks linked to the number of births, since it is generally young dolphins and adults without immunity that are affected.' In the main, the disease causes nervous, respiratory and digestive problems in contaminated cetaceans.

Since 2003, the Departmental Veterinary Laboratory (overseen by the Herault Departmental Council) and CIRAD have been studying morbilliviruses. They are currently the only organisations conducting such analyses in France.

The fact that a morbillivirus was responsible was demonstrated by viral analyses of tissue samples from infected animals. By isolating genome fragments, CIRAD traced the origin of the virus: it stemmed from the epidemic that began in Spain.

Analyses are continuing, and will do so for some time. The aim is to monitor the evolution of the disease and identify the risk factors, so as to control the epidemic. However, there are no plans to develop a vaccine, given the difficulty of vaccinating wild animals.