Effect of dietary chitosan on immune response and disease resistance in Cyprinus carpio

Abstract

BACKGROUND: Occurrence of resistance against antibiotics<br />and inadequate efficacy of some vaccines necessitates studies of<br />natural immunostimulators in aquaculture. Shrimps shell derived<br />from Chitosan can be used as immune stimulators in fish.<br />OBJECTIVES: In this study, the effects of oral administration of<br />chitosan, derived from shrimp shell, on some immune responses<br />and disease resistance in Cyprinus carpio were studied. METHODS:<br />Three hundred healthy fish weighing 42.4+8.1 g were divided into<br />4 equal groups: the first group (G10) was fed with food<br />supplemented with 10 mg kg-1 chitosan, the second (G5) and third<br />groups (G2.5) were fed with food supplemented with 5 mg kg-1 and<br />2.5 mg kg-1, respectively. The control group was fed with basal feed<br />(without chitosan). All groups were treated for 60 days. Blood<br />samples were taken on 0, 20, 40, and 60 days post- experiment; In<br />addition, some immunological indices, including serum lysozyme<br />activity, serum bactericidal activity, Nitro Blue Tetrazolium (NBT)<br />reduction activity, serum proteins, white blood cell count (WBC),<br />and differentiated count were measured. At the end of the treatment,<br />fish were challenged with live Aeromonas hydrophila and mortality<br />rate was recorded for 14 days. RESULTS: Oral administration of<br />chitosan (0.5 and 1%) significantly enhanced NBT reduction<br />activity and resistance to A. hydrophila infection (p=0.012). Serum<br />lysozyme and bactericidal activity, serum total protein and<br />globulin, WBC and leukocytes ratio showed no significant change<br />among the groups (p>0.05). CONCLUSIONS: This study indicates<br />that oral administration of shrimp shell chitosan may have a positive<br />effect on some immune parameters and resistance against bacterial<br />infection in Cyprinus carpio.