Abstract
The current study evaluated the effects of a methanol extract from Chaetomorpha aerea (a green alga) on non-specific immune responses and resistance against Edwardsiella tarda infection in Labeo rohita. Different doses of the extract (5, 50 and 500 mg/kg of body weight) were injected into the fish intraperitoneally while a control group was injected with 0.2 mL of sterile physiological salt solution. Variations in several immunostimulatory parameters (i.e., neutrophil, serum lysozyme, myeloperoxidase, serum antiprotease, and ceruloplasmin activity), reactive oxygen species (ROS) and reactive nitrogen species (RNS) were assessed after 7, 14, 21, and 28 days of post stimulation. E. tarda culture was injected into the fish after 28 days of post stimulation to induce infection to monitor fish mortality within 14 days. Interestingly, all doses of methanolic extract enhanced neutrophil, lysozyme, and myeloperoxidase activity, ROS and RNS, while a dose of 50 mg/kg was the most effective. Fish injected with this optimal dose were also protected against infection with virulent strain of E. tarda. The results of the study suggest that C. aerea extract is a potential prophylactic agent against bacterial infections in finfish.
Highlights
Aquaculture has drawn a great deal of attention during the last few decades due to the recognition on its potent role in meeting nutritional requirements, providing employment, and generating foreign trade [1]
Findings of the present study indicated that all doses of methanolic extract significantly increased neutrophil, lysozyme, and myeloperoxidase activity, as well as reactive oxygen species (ROS) and reactive nitrogen species (RNS)
Outcomes of the study suggest that the methanolic extract of C. aerea exerts a protective effect in L. rohita against E. tarda infection
Summary
Aquaculture has drawn a great deal of attention during the last few decades due to the recognition on its potent role in meeting nutritional requirements, providing employment, and generating foreign trade [1]. The incidence of infectious diseases in farmed fish has been increased. In line with such situation, research efforts on defense mechanisms against microbial attacks in fish are increasing [2]. A chemical, drug or action may be considered as an immunostimulant if it enhances the defense mechanisms or immune responses that improve resistance to diseases [6]. Both specific and non-specific defense mechanisms play crucial roles in control of microbial fish infections. Fish metabolism in particular depends on non-specific defense mechanisms [7]
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