I am studying Sphaerothecum destruens, an invasive parasite that arrived in Europe from China in the 1960s, in conjunction with Pseudorasbroa parva, a fish that is a healthy carrier of the parasite. It is capable of infecting a wide range of hosts and therefore poses problems both in natural fish populations and in aquaculture. The aim of my thesis is to sequence and study the genome of different populations of this parasite in order to search for possible diversity, particularly within the pathogenicity genes, which could explain the generalist nature of this parasite.