The experiment was conducted to evaluate the prevalence ofLernaea cyprinacea and its effects on growth, hematology and skin histopathology ofCatla catla in four experimental earthen ponds (P1, P2, P3 and P4) for 90 days. The growth performance, prevalence ofLernaeacyprinacea and ulceration was recorded on a fortnightly basis. The highest final body weight was observed in P4 (413.7 g) followed by P2 (378.7 g) and P1 (359.8 g) compared to P3 (357.8 g). Increase of Lernaeacyprinacea infection in the first half of the study was from 20.51% - 36.25% in P1, 17.75% -25.25% in P2, 6.5% - 10% in P3 and 14.75% - 13.1% in P4. Ulceration percentage in fish was significantly higher during August and September than May to July. Histopathological studies of skin showed a huge difference between healthy and infected fish skin. Hematological parameters such as hemoglobin (Hb), total erythrocytes count (TEC), total leukocyte counts (TLC) and packed cell volume (PCV%) of non-infected fish exhibited significantly higher values than that of infected fish. Other parameters like erythrocytes sedimentation rate (ESR), neutrophils, eosinophils, lymphocytes, basophils, monocytes and thrombocytes of infected fish showed significantly higher values than those of non-infected fish. In conclusion the exposure to parasites illustrated significant decrease in the Hb, TEC, TLC and PCV% and increase in ESR and other blood cells concentration showed significant severity of parasitic infection.

Keywords:Catla catla, Growth, Lernaea, Histopathology, Hematology.