DNA probes as potential tools for the detection of Marteilia refringens

Since its first description, the paramyxean parasite Marteilia refringens h as been recognized as a significant pathogen of bivalve mollusks. The exist ence of a complex life cycle was postulated by many authors. Here we report the development of DNA-based detection assays as powerful tools to elucida te the Marteilia refringens life cycle. After alignment of the Marteilia re fringens ribosomal DNA small subunit sequence with those of various eukaryo tic organisms, polymerase chain reaction primers were designed. Specific pr imers were used to amplify DNA extracted from purified Marteilia refringens and infected hosts. The specificity of amplified fragments was confirmed b y Southern blotting with an oligoprobe. For in situ hybridization, four pro bes were tested for specific detection of 18S rRNA isolated from Marteilia refringens and other eukaryotic cells by Northern blotting. The most specif ic probe, Smart 2, was successfully used to detect Marteilia refringens by in situ hybridization in infected oysters and mussels.