The experiment was conducted for the duration of three months in four earthen ponds each having dimension 21 xl 3. 5x2. I m (length x width x depth) to evaluate the prevalence of Lernaea spp. and its effects on the growth of Catla catla (Thaila) and hematology and skin. The data regarding the growth performance, Lernaea and ulceration prevalence of fish was recorded on fortnightly basis. The parasite was individually collected from each fish in all four ponds after fifleen days and a detailed microscopic examination of all individuals was done. The species found in the pond fish was identified as the Lernaea cyprincaea.
Our results show the highest weight gain was observed in the pond 4 (413.7 g) followed by pond 2 (378.7 g) and pond 1 (359.8 g), and pond 3 showed the lowest weight gain (357.8 g). There was no significant difference between weight gains of Catla catla irrespective of the prevalence of lernaea species. The highest length increment was observed in the pond 2 (17.5 cm) followed by pond 1 (14.04 cm) and pond 3 (12.1). The lowcst length increment was in pond 4 (11.89 cm). There was no significant difference between initial and final length gain of Catla caila irrespective of the prevalence of lernaea species infestation in all ponds.
At the start of studies there was no infestation of lernaea on thaila. Fish was healthy and fast growing but after fifteen days of stocking L. cyprincaea infestation was observed. infestation was observed in all ponds. There was gradual increase in the rate of infestation till half of the experimental duration irrespective of the environmental changes in all ponds. Increase in the L. cyprincaea percentage in first half of the study was from 20.51% - 36.25% in pond no.1, 17.75% -25.25% in pond no.2, 6.5% - 10% in pond no.3 and 14.75% - 13.1% in pond no.4. In the second half of the experiment fish was treated with KMnO4 @ 1 ppm and common salt @ 1% of total water volume in the second half of the experiment there was a gradual decrease in the lernaea percentage due to treatment. However, the proliferation of the lernaea remained after some time of the treatment, although the lernaea percentage was decreased at the end of study. Decrease in the second half of the study was from 6.9%-5% in pond no.1, 5% - 6.45% in pond no.2, 10.83% -5% in pond no.3 and 5.7% - 5% in pond no. 4. The percentage of L. cyprinacea infestation was compared and there was significant increase in the percentage of Lernaea with the passage of time. However, after the treatment there was a significant decrease in the Lernaea percentage at the end of study. The ulceration percentage in fish was also studied in relation to the Lernaea prevalence and it showed good correspondence and higher the prevalence with higher the ulceration was observed. The ulceration percentage showed a significant difference with respect to time.
The histopathological studies of thaila showed a vast difference b/w healthy and lernaeid fish skin. Healthy thaila skin has no change and variation in its structure while lernaeid thaila skin showed deep variation and ulceration. Skin burst from epidermis and cutis till lower connective tissues.
Study of hematological parameters of lernaeid and non lernaeid fish blood exhibited a significant decreased in Neutrophils, Eosinophils, Lymphocytes, Basophils, Monocytes and Thrombocytes count duration of the blood collection was four months. With respect to duration of exposure to parasites significant increase in the Hb and ESR and decrease in TEC, TLC, PCV and DLC show significant severity of parasitic infection.