effect of dietary chitosan on immune response and disease resistance in cyprinus carpio

background: occurrence of resistance against antibioticsand inadequate efficacy of some vaccines necessitates studies ofnatural immunostimulators in aquaculture. shrimps shell derivedfrom chitosan can be used as immune stimulators in fish.objectives: in this study, the effects of oral administration ofchitosan, derived from shrimp shell, on some immune responsesand disease resistance in cyprinus carpio were studied. methods:three hundred healthy fish weighing 42.4+8.1 g were divided into4 equal groups: the first group (g10) was fed with foodsupplemented with 10 mg kg-1 chitosan, the second (g5) and thirdgroups (g2.5) were fed with food supplemented with 5 mg kg-1 and2.5 mg kg-1, respectively. the control group was fed with basal feed(without chitosan). all groups were treated for 60 days. bloodsamples were taken on 0, 20, 40, and 60 days post- experiment; inaddition, some immunological indices, including serum lysozymeactivity, serum bactericidal activity, nitro blue tetrazolium (nbt)reduction activity, serum proteins, white blood cell count (wbc),and differentiated count were measured. at the end of the treatment,fish were challenged with live aeromonas hydrophila and mortalityrate was recorded for 14 days. results: oral administration ofchitosan (0.5 and 1%) significantly enhanced nbt reductionactivity and resistance to a. hydrophila infection (p=0.012). serumlysozyme and bactericidal activity, serum total protein andglobulin, wbc and leukocytes ratio showed no significant changeamong the groups (p>0.05). conclusions: this study indicatesthat oral administration of shrimp shell chitosan may have a positiveeffect on some immune parameters and resistance against bacterialinfection in cyprinus carpio.