In vitro bioassay
The in vitro test was performed as per (Ekanem et al. 2004) protocol. The lice (Argulus spp.) of heavily infested fish was gently picked with the help of plastic forceps and put into a Petri dish and actively moving parasites were selected with the help of a small hairbrush. Ten live active parasites were manually transferred into a Petri dish containing 20 ml of different concentrations of working Azadirachtin test solution. At every 30 min, the numbers of killed parasites were counted. Parasitic death was considered when the organism did not exhibit any movement after 5 min of observation and after a slight touch with a feather forceps. The experiment was conducted with working test solution in triplicate and compared with a control group under the same test conditions with 2% DMSO solution but with no Azadirachtin