Abstract

• Cirrhinus mrigala, Mrigal carp was sampled monthly and examined myxosporean parasitic infection in kidneys of fish, over 12 months of study period. Myxobolus sp. under the phylum Cnidarian was recorded. Spores of Myxobolus sp. elongated and ellipsoid in valvular view, measurement 11.6µm±1.1µm in length and 7.6µm±0.8µm in width. The highest prevalence of Myxobolus sp. infection were recorded in August (82%) with highest mean intensity of infection (3) when the fish was one year old. Among the infected fish, only 16.7% of infected fish showed cysts formation on the kidneys through the study period. The histology slides of infected tissues were examined under light microscope to understand the histopathological changes of infested tissues. Histopathological changes such as abnormalities of convoluted tubules, dilation of blood vessels, hypertrophy and deformities of glomerulus, and congestion of blood cells caused by Myxobolus infection were observed. Dilation in the capillaries and vacuolar degeneration in the epithelium of renal tubules were observed. The infested kidney tissue showed the prominent circular vacuolar spaces filled with damaged cells necrosis in the tissue. To improve quality fish fry production and successful harvesting, therefore, management practices and pond hygiene should be adopted in nursery operation systems and grow-out ponds.