This study tested drugs and therapeutic compounds to determine effective commercial treatment for fishes infected with myxosporeans. Two series of shore-based experiments and 1 field trial were performed. For the shore-based experiments we used Puntazzo puntazzo (ca. 20 g weight) with kidneys infected with Myxobolus sp. Initially, 6 different doses of Fumagillin, 2 doses of Toltrazuril, and 1 dose of Amprolium, ESB3 and Salinomycin were tested. In the second shore-based experiment, infected fish were treated with Origanum essential oils, Toltrazuril with propylene glycol, Amprolium, and a combination of Salinomycin 12% + Amprolium (SA). In the field trial, P. puntazzo (ca. 165 g) infected with the parasite were treated with SA, Origanum essential oils and Fumagillin. In all trials, the drugs were added to the feed and administered according to the selected regimen. Their efficacy was evaluated in terms of mortality (acceptable level was < 3%), pathology and prevalence rate of Myxobolus sp. Lesions were observed only in fish treated with Fumagillin and Toltrazuril. Pathology due to treatment with Fumagillin was observed only at doses > 6 mg kg -1 body wt for 6 wk in the interstitial renal tissue, where slight inflammation arose. The highest dose tested (25 mg kg -1 ) also produced necrosis in the interstitial tissue, degeneration of the epithelial cells of the tubules and a reduction in melanomacrophage centre numbers. The SA combination proved the most effective treatment for Myxobolus sp. infection of P. puntazzo as (1) the therapeutic regimen and commercial product was not toxic and (2) a significant reduction occurred in the prevalence rate.
KEY WORDS: Puntazzo puntazzo · Anti-myxosporean treatment · HistopathologyResale or republication not permitted without written consent of the publisher Dis Aquat Org 62: [217][218][219][220][221][222][223][224][225][226] 2004 Athanassopoulou 1998a, Rigos et al. 2000, Athanassopoulou et al. 2003. Although researchers have made major advances in regard to antibiotic treatments, sensitivity and drug residues in tissues, progress in the field of antihelminthic treatment of warmwater fishes (such as sea bream and bass) is very limited. There are no licensed antiparasitic compounds for Mediterranean species or official minimal residue limits (MRLs) currently available and all information is extrapolated from coldwater species, especially salmonids. This can cause problems, as treatment conditions differ greatly in terms of environmental (temperature, pH, stability, toxicity to other aquatic animals) and individual (safety, metabolism, stress, residues) factors.The taxonomy, epidemiology and pathology of myxosporean parasites other than Myxidium leei infecting Puntazzo puntazzo have not been well studied, and few reports exist (Athanassopoulou et al. 1998, Mladineo 2003 making the identification very difficult. An unidentified Myxobolus species has been reported from the small intestine of annular sea bream Diplodus annularis in Croatia (Mladineo 2003) in low nu...