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Diseases of Aquatic Organisms

    DAO prepress abstract   -  DOI: https://doi.org/10.3354/dao03465

    Epizootics of epizootic ulcerative syndrome among estuarine fishes of Kerala, India, under post-flood conditions

    T. G. Sumithra*, T. V. Arun Kumar, T. R. Swaminathan, V. N. Anusree, P. V. Amala, K. J. Reshma, T. G. Kishor, R. Ratheesh Kumar, S. R. K. Sharma, V. Kripa, D. Prema, N. K. Sanil

    *Corresponding author:

    ABSTRACT: Epizootic ulcerative syndrome (EUS), primarily caused by Aphanomyces invadans, is an Office International des Epizootics notifiable disease, having potential impacts on fisheries. The paper reports EUS epizootics among estuarine fishes of Kerala, India, during 2018, under post-flood conditions 3 decades after its primary outbreak. Six fish species (Mugil cephalus, Platycephalus sp., Scatophagus argus, Arius sp., Planiliza macrolepis and Epinephelus malabaricus) were infected; forming the first confirmed natural case in E. malabaricus and P. macrolepis. Salinity, surface temperature, dissolved oxygen and pH of resident water during the epizootic was <2 ppt, 25°C, 4.1 ppm and 7.0, respectively. The presence of zoonotic bacterial pathogens in tissues of affected fish (Aeromonas veronii, Shewanella putrefaciens, Vibrio vulnificus and V. parahaemolyticus) revealed through the study advocates that EUS-infected fish may pose a public health hazard if not handled properly. Lack of clinical evidence in the region during last 3 decades, a high number of affected fishes, including 2 new fish species, severity of skin lesions and very low water salinity (<2 ppt) during the outbreak in contrast to historical water salinity records propose relatively recent invasion by A. invadans. Phylogenetic analysis based on internal transcribed spacer region of the rRNA gene showed that the same clone of pathogen has spread across different continents regardless of fish species and ecotypes (fresh/estuarine environments). Altogether, the present study provides baseline data which can be applied in EUS management strategies within brackish-water ecosystems as well as warrants strict surveillance and development of sound biosecurity measures against the disease.