Spirorchiid flukes inhabit the cardiovascular systems of endangered marine turtles, affecting multiple organ systems and contributing to strandings and mortalities worldwide1,2. Few studies have explored spirorchiid species assemblages, host-parasite relationships and species-specific pathogenicity. Spirorchiid eggs, rather than adults, are probably the cause of the most significant pathology1,2. Morphological identification of eggs beyond genus level is generally not possible due to their morphological similarity, hence it is difficult to attribute pathogenic effects to individual species. Additionally, antemortem diagnosis using traditional methods (eg. faecal flotation) is unreliable. This study aims to expand the currently limited genetic database for spirorchiids, develop a means for identifying mixed spirorchiid eggs in tissues, and investigate the relative pathogenicity of individual species. This will lead to the development of a targeted antemortem diagnostic test for investigation, surveillance and control purposes. Deceased turtles from the central/south coast of Queensland, Australia were obtained from government or rehabilitation organisations and examined for spirorchiid infection. Morphological and molecular methods were used to identify adult flukes collected and build a catalogue of spirorchiid species present in the region. DNA sequences obtained were used to develop a multiplex PCR with genus specific primers, used in conjunction with restriction fragment length polymorphism (RFLP) and capillary electrophoresis to differentiate between species. Initial results have identified nine species in this area, with potential cryptic speciation occurring in populations from different ocean regions (ie. Pacific vs. Atlantic Oceans)3. Phylogenetic evidence also suggests that the validity of the genus Learedius should be reviewed3. The new genetic tools now allow investigation of the relative pathogenicity of individual spirorchiid species, and development of a blood based real-time PCR for the diagnosis and surveillance of pathogenic spirorchiids. With these tools, we ultimately hope to aid the rehabilitation and conservation of Queensland marine turtles through improved understanding and treatment of spirorchiid infection.