Saprolegnia parasitica zoospore activity and host survival indicates isolate variation in host preference

The ubiquitous freshwater pathogen Saprolegnia parasitica has long been considered a true generalist, capable of infecting wide range fish species. It remains unclear, however, whether different isolates this pathogen, obtained from distinct geographic locations and host species, display differences in preference. To assess this, the current study examined induced zoospore encystment responses four S. towards skin While three displayed ‘specialist’ responses, one appeared to be more ‘generalist’. In vivo challenge infections involving salmon sea trout with ‘generalist’ (salmon isolate EA001) (sea EA016) did not support vitro findings, no apparent preference reflected infection outcomes. Survival though was significantly following (EA016) isolate. These results indicate that while can generalists, they may target hosts which have frequently exposed (potential local adaptation). Understanding could aid our understanding epidemics help development management procedures.