Author(s): C.Muthu Ramakrishnan, M.A.Haniffa, P.Jeya Sheela

Abstract: Heteropneustes fossilis, commonly called singhi is an obligatory air- breathing fish occurring shallow inland waters of India. For the past two decades this species is declining due to habitat loss, high fishing pressure and easy prone to Epizootic Ulcerative Syndrome (EUS). The infected individuals showing external symptoms like unresponsiveness, wounds, superficial lesions, swelling, discoloration, and deep ulcerative hemorrhages were subjected to bacteriological examination and the pathogens associated with EUS were isolated. The highest microbial load 6.3 ± 0.4 × 107 cfu g-1 was observed in muscle followed by 5.7 ± 0.6 106 cfu g-1 in gills and 7.2 ± 0.9 × 105 cfu g-1 in liver whereas the lowest load 4.3 ± 0.7 × 104 cfu g-1 was found in intestine. Similarly, a higher percentage of A. invadans (15%) and A. hydrophila (12.5%) was determined from the muscle of the diseased H. fossilis whereas the same was found to below in the intestine (6% and 5.5% respectively). One fungal species, Aphanomyces invadans and nineteen bacterial species were isolated and identified. Among the 20 isolates, A. invadans was the onlyrnfungus and A. hydrophila was dominant among the bacterial isolates from muscle, gill, liver and intestine.

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