The lymphocystis disease virus (LCDV) is a widespread disease in Mediterranean aquaculture and could lead to losses in fry as well as prevent the sale of adult gilthead seabream (Sparus aurata), affecting both hatchery and on-growing stages. Although LCDV infections are often considered self-limiting, they can lead to severe outcomes due to skin microbiome alterations that promote secondary infections, while also reducing growth and marketability, causing substantial economic losses. Basic biosecurity measures are not successful, and there is no available commercial vaccine. This study evaluated diets supplemented with Origanum vulgare and Cinnamomum zeylanicum essential oils (1% and 2%) in gilthead seabream experimentally infected with LCDV. Preventive feeding (90 days before infection) and therapeutic feeding (initiated at infection) were compared across 11 experimental groups, including infected, recovered, and control groups. Results showed that essential oils were more effective prophylactically than therapeutically, highlighting their protective role when incorporated into diets. Cinnamon-supplemented groups consistently exhibited lower prevalence and mortality than oregano groups. High DNA damage values linked to reduced mortality, particularly in the CIN90.1 group, demonstrated that viral dissemination was most restricted. In conclusion, essential oils modulated LCD progression by influencing viral interactions with DNA damage repair mechanisms, supporting their potential for disease control in intensive aquaculture.

As aquafeed formulations include more plant-based materials, mycotoxin contamination is becoming relevant for fish farming. Deoxynivalenol (DON) and fumonisin B1 (FB1) frequently occur in fish feeds and may impair fish performance and health. This study evaluated the impact of DON and FB1 on growth and health parameters in gilthead seabream (Sparus aurata). Fish were fed ad libitum for seven weeks with six diets assessed in triplicate: DON A (300 ppb), DON B (2000 ppb), DON C (5000 ppb), FB1 A (5 ppb), FB1 B (10 ppb), FB1 C (40 ppb). The highest contamination levels significantly reduced feed intake, body weight, total length, and biomass, while body weight was also reduced in the lowest FB1 treatment. The feed conversion ratio increased in exposed fish, whereas the specific growth rate decreased in DON B, DON C, FB1 A, and FB1 C. Both mycotoxins altered hematological profiles, immune-related enzymatic activities, and liver morphology. DNA damage increased with exposure level and was greatest at the highest DON concentration. Overall, this study shows that short-term dietary exposure can impair seabream performance and health, supporting stricter mycotoxin monitoring in fish feeds and research on chronic exposure, recovery, and species-specific safety thresholds.