Rathod Sanjaykumar Karsanbhai, Das Basanta Kumar, Tandel Ritesh Shantilal, Chatterjee Sohini, Das Nilemesh, Tripathi Gayatri, Kumar Saurav, Panda Satyen Kumar, Patil Prasanna Kumar, Manna Sanjib Kumar
ICAR-Central Institute of Fisheries Education, Mumbai, 400061, India.
ICAR-Central Inland Fisheries Research Institute, Kolkata, 700120, India.
Sci Rep. 2024 Dec 28;14(1):30720. doi: 10.1038/s41598-024-80075-0.
Saprolegniasis is one of the most dangerous fungal diseases of fish, causing significant mortality in fish hatcheries and young ones. The present study aimed to isolate and characterize the causative fungus from fingerlings of Pangasianodon hypophthalmus cultured intensively in freshwater cages in Indian reservoirs and to determine minimum inhibitory concentrations of different antifungal compounds against the fungal hyphae and zoospores. The fungal isolates grown on potato dextrose agar showed an abundance of gemmae, elongated mycelia, non-septate hyphae, primary zoospores, mature zoosporangia with numerous zoospores, cysts with bundles of long hairs and were further identified as Saprolegnia parasitica following PCR amplification and sequencing of internal transcribed spacer region. S. parasitica showed temperature-sensitive optimum growth in a narrow window of 12-24 ℃, which might drive its experimental pathogenesis as well as natural infections in the winter months. In vitro sensitivity testing established negligible inhibitory activity of fluconazole, boric acid, sodium thiosulfate, and potassium permanganate while clotrimazole arrested the spore and hyphal growths at 2 mgL concentration suggesting potential of the imidazole antifungal in treating S. parasitica infection in fish. The present study will serve as the baseline information for developing therapeutic and management strategies for controlling saprolegniasis in the economically significant iridescent catfish.
水霉病是鱼类最危险的真菌疾病之一，在鱼苗场和幼鱼中会导致大量死亡。本研究旨在从印度水库淡水网箱中集约化养殖的苏氏圆腹芒鱼种中分离并鉴定致病真菌，并确定不同抗真菌化合物对真菌菌丝和游动孢子的最低抑菌浓度。在马铃薯葡萄糖琼脂上生长的真菌分离物显示出大量的芽孢、细长的菌丝体、无隔膜的菌丝、初生游动孢子、带有大量游动孢子的成熟游动孢子囊、带有一束束长毛的囊肿，经内部转录间隔区的PCR扩增和测序后，进一步鉴定为寄生水霉。寄生水霉在12-24℃的狭窄温度范围内显示出对温度敏感的最佳生长，这可能会推动其在冬季的实验性发病机制以及自然感染。体外敏感性测试表明，氟康唑、硼酸、硫代硫酸钠和高锰酸钾的抑制活性可忽略不计，而克霉唑在2mg/L浓度下可抑制孢子和菌丝生长，表明咪唑类抗真菌药物在治疗鱼类寄生水霉感染方面具有潜力。本研究将作为制定治疗和管理策略以控制经济上重要的苏氏圆腹芒水霉病的基线信息。
