Hormonal status and phagocytic activity in sea bream infected with vibriosis

Serum taken from female, sexually mature, silver sea bream (Sparus sarba) d isplaying either no symptoms of vibriosis, mild infection, severe infection or moribundity were assayed for a number of key hormones. Serum cortisol l evels were not significantly different among symptomless, mildly- and sever ely-infected groups, whereas moribund fish displayed hypercortisolemia with a 14-fold increase in serum cortisol in comparison to symptomless fish. Se rum estradiol levels were significantly reduced 19-fold in mildly-infected fish and remained at a low level as infection progressed, whereas serum tes tosterone increased gradually during vibriosis with a 1.8-fold increase in moribund groups in comparison to symptomless groups. Both serum thyroxine ( T-4) and triiodothyronine (T-3) gradually decreased during vibriosis being 26-and 2.8-fold lower, respectively, in moribund fish in comparison to symp tomless fish. The non-specific immune response, as determined by phagocytic activity, was also assessed using macrophages isolated from the pronephros and spleen of infected fish. Phagocytic indices significantly increased in mildly- and severely-infected fish and then decreased from these stimulate d levels in moribund fish. (C) 2001 Elsevier Science Inc. All rights reserv ed.