A questionnaire-based survey on the presence of red mark syndrome in Italian rainbow trout (<i>Oncorhynchus mykiss</i>) farms

Red mark syndrome (RMS) is a widespread skin disease of rainbow trout ( Oncorhynchus mykiss) . Its aetiological agent believed to be Midichloria -like organism, an intracellular bacteria the order Rickettsiales. RMS has been reported on several occasions, however, comprehensive analysis epidemiology this and its actual economic impact aquaculture industry missing. Through questionnaire-based survey, we estimated prevalence implications infection farms in Italy 2020-2021. One hundred nine farms, representing 64% (around 22,000 tons) total national production, were surveyed. In short, results show that Italian consistently persistently present territory, affecting about 30% farms. observed have similar features those generally described literature. Clinical more often springtime; size-wise, most commonly affected groups are fish close market size weighing less than 100g (22% cases). Most interestingly, recurrence clinical signs same batch was cases. Despite diffusion, not perceived as major concern sector, mainly due intermittent nature, low mortality spontaneous resolution. The main costs associated with related antibiotic treatment commercial downgrading; it impossible estimate these production costs.