Abstract
The potential anthelmintic efficacy of dietary caprylic acid against the monogenean Sparicotyle chrysophrii in cage-reared gilthead sea bream, Sparus aurata was investigated in this study. The selection of caprylic acid dosing for the field trials was based on laboratory kinetic experiments performed at 20–21 °C water temperature. A single in-feed administration of 200 mg/kg fish showed a superior distribution profile compared to 100 mg/kg fish. Based on samplings performed from 0.5 to 24 h post administration, caprylic acid tissue levels were measured earlier and remained longer in gilthead sea bream serum, gills and skin after double dosing while they were significantly higher compared to low dosing tissue levels when measurable concentrations were observed at the same sampling points.
Therapeutic application of caprylic acid was carried out for 60 d in two farming units with noticed S. chrysophrii infection and water temperature ranged from 15 to 22 °C. At the commence of the experiment in the first farm, prevalence (44–47%) and mean intensity (1.1–1.5 adults) of S. chrysophrii were low but both showed an increasing pattern while the experiment was progressing. At the final sampling, mean intensity was significantly reduced in fish treated with caprylic acid (6 ± 2.6 vs 14.1 ± 3.1), while growth remained unaffected. A higher infestation with S. chrysophrii was already established at the initiation of therapy in the second farm. Prevalence was 100% in both groups and intensity reached values up to 17 adults. Both parameters remained at high levels 30 and 60 d after the start of the trial. Growth and parasitic intensity between experimental groups were not significantly affected by caprylic acid treatment during the 2-month medication period.
It is concluded that a dietary dosing of 200 mg caprylic acid/kg for 60 d can significantly affect S. chrysophrii intensity in cage-reared gilthead sea bream when treatment is implemented at the first disease stages. It is thus recommended that the progress of the disease should be continuously monitored in the farmed population during the production cycle and administration of caprylic acid should be initiated prior to the development of the infection.
Keywords
• Sparicotyle chrysophrii;
• Caprylic acid;
• Antiparasitic;
• Tissue distribution gilthead sea bream;
• Sparus aurata