Protective effect of chitin and chitosan enriched diets on immunity and disease resistance in Cirrhina mrigala against Aphanomyces invadans

• WBC, RBC, Ht increased in 1% chitin and chitosan diets from weeks 1 to 4.
• Total protein and albumin significantly increased in all diet on weeks 2 and 4.
• Phagocytic and lysozyme activities enhanced in both diet on weeks 2 and 4.
• Complement activity was enhanced in chitosan diet from weeks 1 to 4.
• Cumulative mortality was low in fish fed with 1% of chitin and chitosan diets.

The effect of diet enriched with 1% chitin or chitosan on innate immune response and disease resistance in Cirrhina mrigala against Aphanomyces invadans was investigated at weeks 1, 2, and 4. In the un-infected and infected groups the white blood cells (WBC), red blood cells (RBC), haematocrit (Ht), lympocytes, monocytes, and neutrophils significantly increased when fed with 1% chitin (CH) or chitosan (CT) enriched diet from weeks 1 to 4 when compared to control; however, the haemoglobin (Hb) and thrombocytes significantly increased only on weeks 2 and 4. The total protein and albumin levels also significantly increased with any enriched diet on weeks 2 and 4; but the globulin and albumin:globulin ratio increased on week 4 as compared to control; similarly the phagocytic activity significantly increased on weeks 2 and 4 while the lysozyme activity increased from weeks 1 to 4. The complement activity was significantly enhanced in CT and CTI fed groups on weeks 2 and 4. In un-infected fish fed with 1% CH and CT diets, the cumulative mortality was 10% and 5% whereas the infected fish suffered 20% and 25% mortality. The present results suggest that infected fish fed with 1% chitin or chitosan enriched diet modulates the immune system conferring disease resistance in C. mrigala against A. invadans.