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Diseases of Aquatic Organisms

    DAO prepress abstract   -  DOI: https://doi.org/10.3354/dao03567

    Outbreaks of epizootic ulcerative syndrome in Kerala, India following episodes of flooding

    Bini C. Das, Divya V. Haridas, Nithin Jacob, Arunendhu Ramakrishnan, P. H. Anvar Ali, V. J. Rejish Kumar, Devika Pillai*

    *Corresponding author:

    ABSTRACT: Large scale fish mortality was observed in flood affected fish farms in several parts of Kerala following heavy rainfall in August 2018 and 2019, which was nearly 53% above the normal monsoon rain that the region receives. The affected fish had severe haemorrhages and ulcers, typical of the highly infectious disease epizootic ulcerative syndrome (EUS) caused by the water mould Aphanomyces invadans. In freshwater, snakeheads Channa spp. were severely affected, while in brackish water mullet (Mugilidae) and pearl spot Etroplus suratensis were more severely affected. EUS was observed for the first time in four freshwater fishes: dotted sawfin barb Pethia punctata (Cyprinidae), Malabar leaffish Pristolepis malabarica (Pristolepididae), mahecola barb Puntius mahecola (Cyprinidae) and giant snakehead Channa pseudomarulius (Channidae). The cause of the mortality was confirmed to be EUS by histology and molecular diagnosis. The fungal hyphae was also observed in deeply ulcerated fish by lactophenol cotton blue staining. The severity of the EUS outbreak is linked to the sudden change in water quality associated with the flood such as low water temperature, drop in pH, total alkalinity and total hardness.