Non-invasive detection method for Bonamia ostreae infected Ostrea edulis

Abstract

Populations of the native European flat oyster (Ostrea edulis) have been in decline for the past two centuries through a combination of exploitation, disease and climatic events. Ongoing efforts to restore these animals to suitable habitats throughout Europe are increasing in number and magnitude but have been hindered by pathogens such as the protist parasite Bonamia ostreae. Detecting such pathogens in animals before relocation to disease-free restoration or farm sites remains a major issue. Current detection methods rely on sacrificially dissecting a subset of the animals to perform qPCR and histology. While very sensitive, this method is destructive and the animals which are moved are themselves untested. Here, we present a non-invasive scalable method to detect Bonamia ostrea in O. edulis. Following overnight quarantine in aerated seawater, faeces and pseudofaeces produced by the oysters is collected. The DNA is extracted from this material and analysed by qPCR for presence of the pathogen. This approach proves more sensitive for pathogen detection than eDNA sampling from the water alone. Furthermore, when tested alongside conventional histology and tissue-extracted DNA qPCR results, our method demonstrated comparable sensitivity levels. Future studies aim to adapt this method to detecting other aquatic diseases or invasive species but it should be noted that this may be a pathogen-specific characteristic.