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Diseases of Aquatic Organisms

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DAO 139:1-13 (2020)  -  DOI:

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

T. G. Sumithra1,*, T. V. Arun Kumar2, T. R. Swaminathan2, V. N. Anusree1, P. V. Amala1, K. J. Reshma1, T. G. Kishor4, R. Ratheesh Kumar5, S. R. Krupesha Sharma1, V. Kripa3, D. Prema3, N. K. Sanil1

1Marine Biotechnology Division; ICAR-Central Marine Fisheries Research Institute (ICAR-CMFRI), Post Box No. 1603, Kochi-682 018, India
2National Bureau of Fish Genetic Resources, Canal Ring Road, PO Dilkusha, Lucknow 226 002, India
3Fishery environment Management Division, ICAR-CMFRI, Kochi-682 018, India
4Fishery Resources Assessment Division, ICAR-CMFRI, Kochi-682 018, India
5Crustacean Fisheries Division, ICAR-CMFRI, Kochi-682 018, India
*Corresponding author:

ABSTRACT: Epizootic ulcerative syndrome (EUS), primarily caused by the water mold Aphanomyces invadans, is an OIE-notifiable disease, having potential impacts on fisheries. We report 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, including the first confirmed natural case in E. malabaricus and P. macrolepis. Salinity, surface temperature, dissolved oxygen and pH of resident water during the epizootic were <2 ppt, 25°C, 4.1 ppm and 7.0. The presence of zoonotic bacterial pathogens (Aeromonas veronii, Shewanella putrefaciens, Vibrio vulnificus and V. parahaemolyticus) in tissues of affected fish indicates that EUS-infected fish may pose a public health hazard if not handled properly. Lack of clinical evidence in the region during the last 3 decades, a high number of affected fishes, including 2 new fish species, the severity of skin lesions and very low water salinity (<2 ppt) during the outbreak in contrast to historical water salinity records suggest relatively recent invasion by A. invadans. Phylogenetic analysis based on the 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. We recommend strict surveillance and development of sound biosecurity measures against the disease.

KEY WORDS: Aphanomyces invadans · Epinephelus malabaricus · Planiliza macrolepis · Salinity

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Cite this article as: Sumithra TG, Kumar TVA, Swaminathan TR, Anusree VN and others (2020) Epizootics of epizootic ulcerative syndrome among estuarine fishes of Kerala, India, under post-flood conditions. Dis Aquat Org 139:1-13.

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