Modulation of the innate immune response of rohu Labeo rohita (Hamilton) by experimental freshwater lice Argulus siamensis (Wilson) infection

The study was undertaken to determine the modulation in innate immune response of rohu (Labeo rohita) during experimental freshwater lice Argulus siamensis infection. Results showed that serum alpha-2 macroglobulin (alpha-2M) activity, ceruloplasmin level and alternative complement activity were significantly (P < 0.05) lower in fish at different degrees of lice infection in comparison with uninfected control. No significant difference (P > 0.05) in haemagglutination titre was observed in fish with low- and high-degree lice infections as compared with uninfected control. The serum lysozyme level was significantly (P < 0.05) lower in low degree of lice infection as compared with control fish. The total serum antiprotease, myeloperoxidase activity and total protein level were not significantly different (P > 0.05) in different degrees of lice-infected fish with respect to the control fish. The study indicated that A. siamensis infection modulated the immune system of rohu by suppressing the alpha-2M, serum complement activities and ceruloplasmin level and through induction of stress response. The baseline data obtained in the present study have tremendous importance in understanding the susceptibility of rohu to different degrees of parasitosis and might be useful in controlling this dreaded ectoparasitic infection in fish.