NONSPECIFIC CELLULAR AND HUMORAL DEFENCE MECHANISMS IN SHEATFISH (Silurus glanis)

Early diagnosis of fish diseases by control of immunological parameters is one of the most important part of prophylactic in intensive fish culture. For the first time, the nonspecific cellular and humoral defence mechanisms were studied in farming sheatfish, using two size of fishes weighing 300-500 g and 2000-3000 g. For each group, the respiratory burst activity and the potential killing activity of blood and pronephric phagocytes, the proliferative ability of lymphocytes and the myeloperoxidase activity in PMN cells was measured. The lysozyme and ceruloplasmine activity as well as total proteins and immunoglobulins in serum are also presented. Those results will be used for control the defence mechanisms and protection against infection diseases of sheatfish raised in farming conditions. Sheatfish. aquaculture. nonspecific cellular and humoral immunity Successful commercial production of most cultured fish species has been facilitated by the intensification of larval and fingerling rearing techniques. Siluriformes species are no exception and early attempts at larval rearing in ponds were soon superseded by intensive hatchery production. Traditional aquaculture of Siluriformes in Europe and Asia is more directed towards whole fish products but some traditional processing has been developed, as is found in Africa, to allow for storage of the fish. Recent developments in silurid aquaculture, sheatfish (Silurus glanis) in Europe and catfish (lctalurus punctatus) in USA, have been associated with the future processing of fish (Biology and Aquaculture of Siluriformes, Montpellier 1994). There is, however, little information on the ability of Siluriformes to respond to such processing compared to rainbow trout or to carp, species which are often used as a model for experimental studies. A great deal of information about channel catfish physiology, defence mechanisms and diseases has been published, but concerning other Siluriformes species, we have only little information, especially concerning sheatfish (Silurus glanis). Among all of the viruses known to be pathogenic for fish, only a few are related to diseases of cultured sheatfish. These include: the sheatfish herpes virus (B e ke s i et al. 1981), and the sheatfish iridovirus (Ahne et al. 1989, Ahne et al. 1997, an irido-like agent associated with systemic infections was isolated in France Moreover, the only fish species-specific bacterial pathogen entailing high mortality in the sheatfish culture is Edwardsiella tarda. which has been isolated in LDA 39 (Laboratoir