The tortoise and the herpesvirus
An intuition by Frédéric Gandar, a PhD student at the University of Liege and his thesis supervisor Alain Vanderplasschen to focus on a research topic that has rarely been explored in the scientific world, has paid dividends. The study of Testudinid herpesvirus 3 ( TeHV-3), a herpesvirus causing high mortality rates in several protected species of tortoises (including Hermann’s tortoise), has resulted in several discoveries and has also made front-page in the Journal of Virology(1). Up to the present, the 250 or so herpesviruses studied – these are found in oysters as well as in humans – are divided into six distinct genomic structures. All of them, that is, except Testudinid herpesvirus 3. Frédéric Gandar and Alain Vanderplasschen could not believe their eyes, but they had discovered a new herpesvirus genome structure. This would be the seventh. Virology reference books will need to be updated! And this does not even take into account immune evasion or phylogeny-related discoveries. The researchers are currently working on a vaccine against this disease that is decimating tortoise species many of which are endangered.
When collection rhymes with propagation
The first descriptions of this disease in scientific literature goes back to the 1980s. The propagation of the disease probably accelerated at the same time as people began to collect these reptiles which live mainly in the Mediterranean Basin. Fans of these animals are prepared to spend from 200 to 250 Euros for a classic species or even up to 1,500 Euros for certain specimens. These are the types of figures that apply in the official market. But there is also a parallel unofficial market. Carefree tourists buy tortoises at the corner of the street when they are on holiday or may even pick them up on the side of the road to bring them home in their luggage, blissfully unaware that they are infected. As a result of these practices the virus can spread much more quickly than by natural means. “People are often unaware of the fact, but many species are suffering due to the fact that they have become animals of collection”, says Alain Vanderplasschen. “Certain diseases have become global whereas they would have developed much more slowly in nature, thus perhaps giving the species in question time to adapt to the disease. Because of collection, very different species can come into contact with each other artificially in terrariums…It’s like putting a crocodile and a caribou together in the same place! It is not impossible that what is happening to Testudo tortoises is the expression of the non-adaptation of a virus to a new host and therefore the consequences of a recent transfer of a virus from one species of animal to another”.
(1) Gandar F., Wilkie G., Gatherer D., Kerr K., Marlier D., Diez M., Marschang R., Mast J., Dewals B., Davison A., Vanderplasschen A., The genome of a tortoise herpesvirus (Testudinid Herpesvirus 3) has a novel structure and contains a large region that is not required for replication in vitro or virulence in vivo. Journal of Virology, 89, 22, october 2015.