TY - JOUR

T1 - Saprolegnia parasitica zoospore activity and host survival indicates isolate variation in host preference

AU - Matthews, Emily

AU - Ellison, Amy

AU - Cable, Jo

PY - 2021/4

Y1 - 2021/4

N2 - The ubiquitous freshwater pathogen Saprolegnia parasitica has long been considered a true generalist, capable of infecting a wide range of fish species. It remains unclear, however, whether different isolates of this pathogen, obtained from distinct geographic locations and host species, display differences in host preference. To assess this, the current study examined the induced zoospore encystment responses of four S. parasitica isolates towards the skin of four fish species. While three of the isolates displayed ‘specialist’ responses, one appeared to be more of a ‘generalist’. In vivo challenge infections involving salmon and sea trout with the ‘generalist’ (salmon isolate EA001) and a ‘specialist’ (sea trout isolate EA016) pathogen, however, did not support the in vitro findings, with no apparent host preference reflected in infection outcomes. Survival of sea trout and salmon though was significantly different following a challenge infection with the sea trout (EA016) isolate. These results indicate that while S. parasitica isolates can be considered true generalists, they may target hosts to which they have been more frequently exposed (potential local adaptation). Understanding host preference of this pathogen could aid our understanding of infection epidemics and help with the development of fish management procedures.

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

U2 - https://doi.org/10.1016/j.funbio.2020.11.002

DO - https://doi.org/10.1016/j.funbio.2020.11.002

M3 - Article

VL - 125

SP - 260

EP - 268

JO - Fungal Biology

JF - Fungal Biology

SN - 1878-6146

IS - 4

ER -