Aeromonas veronii is an emerging pathogen causing severe pathology and mortalities in European seabass aquaculture in the Aegean Sea, Mediterranean. More than 50 strains of the pathogen were characterized biochemically and genetically in order to study the epidemiology of the disease, as well as the phylogeny and virulence of the bacterium. Based on the phenotypic characteristics, the isolates form three groups consisting of: (a) the West Aegean Sea, non-motile, non-pigment-producing strains, (b) the West Aegean Sea, motile, and pigment-producing strains and (c) the East Aegean Sea motile strains that produce minute amounts of pigment. All strains were highly similar at the genomic level; however, the pattern of West/East geographic origin was reflected in biochemical properties, in general genomic level comparison and in the putative virulent factors studied. Type VI secretion system was not detected in the western strains. The outer membrane protein (OMP) profile which contains proteins that are putative antigenic factors, was very similar between strains from the different areas. Although most of the OMPs were detected in all strains with great sequence similarity, diversification according to geographic origin was evident in known antigenic factors such as the maltoporin LamB. A systematic comparative analysis of the strains is presented and discussed in view of the emergence of A. veronii as a significant pathogen for the Mediterranean aquaculture.
Intraperitoneal (i.p.) injection vaccination is considered effective to protect European sea bass (Dicentrarchus labrax) from economically important diseases. Water-based as well as oil-adjuvanted vaccine formulations are being widely used. The oil adjuvants used to potentiate antigen effects lead to higher and more prolonged immune response but also to chronic peritoneal inflammatory reactions, regarded as adverse or side-effects. During a three-year field study conducted throughout Greek mariculture, the intra-abdominal lesions were assessed on fish sampled prior to, and at different times post i.p. injection with different oil-adjuvanted vaccine formulations. The scope was to create a macroscopic side-effect intensity scale for sea bass in line with those applicable to salmonids (Salmo salar, Oncorhynchus mykiss) and cod (Gadus morhua). The diversity of lesions observed ranged from none (presumably non-injected; score 0) to widespread, strong adhesions with granuloma, pigmented or not (score 6). The occurrence of small nodules apparently containing vaccine remains, encapsulated by layers of connective tissue is described. The proposed scoring system is described and illustrated, intended to guide farm staff to evaluate the intensity of post-injection vaccination side-effects by necropsy on site.
Background
Henneguya Thélohan, 1892 (Myxobolidae) is one of the most species-rich genera of myxosporean parasites infecting fish. Although common in nature, there are few reports of these parasites causing important disease in aquaculture. In this paper, we describe a new species of Henneguya infecting Pagrus major (Temminck & Schlegel), a fish host introduced to the Mediterranean Sea from Japan in the late 1980s.
Results
Large plasmodia of the parasite were found in the bulbus arteriosus and in the ventricle of the infected fish. Spores were found mainly in the kidney and heart and were accompanied by melanized macrophages or vascular intimal proliferation mixed with a mild non-suppurative response, respectively. Comparisons of morphometric data for spore and polar capsule length and width, suggest a unique combination of features in the newly described species. Molecular analysis, based on 18S rDNA sequence of the parasite, followed by phylogenetic analysis, indicated that the parasite described here is a novel species of Henneguya, clustered with the marine congeneric species.
Conclusions
Henneguya aegea n. sp. infects in aquaculture P. major, a host introduced as eggs to the Mediterranean from Japan. Despite the high host specificity of the myxobolid parasites, H. aegea n. sp. seems to be able to use P. major as a host and propagate successfully, causing morbidity and mortality. This could result in spillback of the new species from high density cultured non-native P. major to native fish hosts.
Abstract. In order to assess the attitudes of fish farmers towards data management, and discover the major sources of influence upon planning production, a postal survey among 293 salmon and trout farmers was conducted in the summer of 1987. The degree of microcomputer use and the uptake of automation were examined in this perspective.
Salmon and trout fanners collected production records which, in most cases, were unsuitable for planning. Microcomputers were used mainly for accounting and word processing. Software was commonly purchased‘off‐the‐shelf’. Computerization when rejected was primarily on grounds of excessive costs and time requirements. Other automation comprised feeding systems and to a lesser extent water parameter monitoring. For decision making, directors and owners relied heavily on their site managers and foremen to provide feedback. When farms were members of marketing cooperatives or owned by larger firms the latter directed their production and outlets. Accountants were employed part‐time to draw the financial accounts, and the proportion of fish farms hiring experts and computer consultants was small. The findings showed that information technology is not a priority among fish farm managers.
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