Abstract
A new skin condition, known as puffy skin disease ( PSD ), emerged in farmed rainbow trout Oncorhynchus mykiss (Walbaum) in 2002. The number of new cases increased considerably from 2006. Clinical signs include white or grey skin patches, which become raised and red with excessive mucous production and scale loss. Fish are inappetant and lose condition. Histologically, the key feature is epithelial hyperplasia. We undertook a questionnaire study of trout farmers in England and Wales to investigate prevalence and risk factors. PSD was reported on 37% ( n = 49) of rainbow trout sites, located in 28 river catchments. The increase in cases from 2006 onwards was mirrored by the increase in red mark syndrome ( RMS ). Prevalence and severity of PSD were highest in the summer months. The presence of PSD was associated with RMS ( OR = 9.7, P PSD ( OR = 5.3. P PSD and practices to manage the disease.