Abstract:
Effects of short term administration of levamisole by immersion on immune responses
of the cultured food fish, Catla catla were investigated. Sub-adults of C. catla were
given two hr bath in 1.25 or 2.5 mg/L levamisole solutions and the immune responses
were assessed on 14, 21, 28, 42 and 56 days after the treatment in comparison to the
controls. Results revealed that leucocrit levels, total leucocyte counts, abundance of
leucocytes, total phagocytic activity, phagocytic index, myeloperoxidase activity and
oxygen radical production by phagocytes were increased significantly in levamisole
treated fish in comparison to the controls. No significant differences in the degree of
immuno-stimulation were seen between the fish groups exposed to the two concentrations
of levamisole tested. For both exposure levels, most of the parameters tested were greatly
elevated on 42 days post exposure to levamisole. Challenge experiments showed that
levamisole treated fingerlings of C. catla co-habitated with gold fish which had been
infected with Ichthyophthirius and Dactylogyrus exhibited lower infestation levels and
mortalities in comparison to the control fish. Levamisole treated C. catla which had
been challenged with Aeromonas hydrophila displayed comparatively less mortalities
compared to the controls. The results support the potential use of levamisole as an
immunostimulant in culturing this fish.