Effects of dietary aloe on chemiluminescent responses of peripheral blood phagocytes and resistance against Edwardsiella tarda Ewing and McWhorter 1965 in the cultured olive flounder, Paralichthys olivaceus (Temminck et Schlegel)

摘要

The non-specific defence is the first line of defence against microbial infection in vertebrates. Farmed fish are inevitably subjected to various kinds of stress that may lead to down-regulation of the non-specific immunity and outbreak of infections. Therefore, an enhanced ability to resist infection can be obtained by activation of the innate immune system (Anderson & Siwicki 1994). Recently, increasing attention has been paid to the use of immunostimulants in disease prevention, especially to those that elevate non-specific immunity of fish (Anderson 1992; Sakai 1999). Aloe leaves possess several important therapeutic properties such as accelerating wound healing, immune stimulation, anticancer, antiviral, bactericidal and bacteriostatic effects in mammals (Lorenzetti, Salisbury, Beal & Baldwin 1964; Solar, Zellwe, Rasolofonirina, Coulanges, Ralamboranto, Andriatsimahavandy, Rakotovao & Le Deaut 1980: Brossat, Ledeaut, Ralamboranto, Rakotovao, Solar, Gueguen & Coulanges 1981: Kahlon, Kemp, Carpenter, McAnalley, McDaniel & Shannon 1991; Zhang & Tizard 1996; Stuart, Lefkowitz, Lincoln, Howard, Gelderman & Lefkowitz 1997). Although Kim, Hwang & Bai (1999) reported a therapeutic effect of aloe-supplemented diets in juvenile rockfish (Sebastes schlegeli, Hilgendorf), which were infected with Vibrio alginolyticus, there is no information available on the immunostimulatory effects of aloe in fish. Therefore, in the present study, the effects of dietary aloe on the chemiluminescent responses of blood phagocytes and resistance against Edwardsiella tarda Ewing and McWhorter 1965 in cultured juvenile olive flounder, Paralichthys olivaceus (Temminck et Schlegel), were investigated.