Asia contributes more than 90% to the world's aquaculture production. Like other farming systems, aquaculture is plagued with disease problems resulting from its intensification and commercialization. This paper describes the various factors, providing specific examples, which have contributed to the current disease problems faced by what is now the fastest growing food-producing sector globally. These include increased globalization of trade and markets; the intensification of fish-farming practices through the movement of broodstock, postlarvae, fry and fingerlings; the introduction of new species for aquaculture development; the expansion of the ornamental fish trade; the enhancement of marine and coastal areas through the stocking of aquatic animals raised in hatcheries; the unanticipated interactions between cultured and wild populations of aquatic animals; poor or lack of effective biosecurity measures; slow awareness on emerging diseases; the misunderstanding and misuse of specific pathogen free (SPF) stocks; climate change; other human-mediated movements of aquaculture commodities. Data on the socio-economic impacts of aquatic animal diseases are also presented, including estimates of losses in production, direct and indirect income and employment, market access or share of investment, and consumer confidence; food availability; industry failures. Examples of costs of investment in aquatic animal health-related activities, including national strategies, research, surveillance, control and other health management programmes are also provided. Finally, the strategies currently being implemented in the Asian region to deal with transboundary diseases affecting the aquaculture sector are highlighted. These include compliance with international codes, and development and implementation of regional guidelines and national aquatic animal health strategies; new diagnostic and therapeutic techniques and new information technology; new biosecurity measures including risk analysis, epidemiology, surveillance, reporting and planning for emergency response to epizootics; targeted research; institutional strengthening and manpower development (education, training and extension research and diagnostic services).

Fish parasites of the Multivalvulida (Myxozoa, Myxosporea) are widespread and can be associated with mortality or poor flesh quality in their commercially important marine hosts. Traditional classifications divide members of this order into families based on spore valve and polar capsule numbers. Analyses of the small-subunit (SSU) ribosomal DNA (rDNA) sequences from all representative families in the order (Trilosporidae, Kudoidae, Pentacapsulidae, Hexacapsulidae, and Septemcapsulidae) indicate that a revision of the taxonomy and nomenclature is warranted. In our phylogenetic analysis of (SSU and large subunit) rDNA sequences, members of Pentacapsula, Hexacapsula, and Septemcapsula root within a clade of Kudoa species with Unicapsula (Trilosporidae) as an outlier to these genera. Therefore, we propose to synonymize Pentacapsulidae, Hexacapsulidae, and Septemcapsulidae with Kudoidae alter the diagnosis of Kudoidae and Kudoa to accommodate all marine myxozoan parasites having 4 or more shell valves and polar capsules.

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-Among mollusc pathogens, paramyxeans are an important group of protistan parasites belonging to the genera Marteilia and Marteilioides. Marteilia refringens and M. sydneyi are of particular concern given their potential impact on mollusc aquaculture world-wide. Aber disease and QX disease are currently listed by the OIE, the World Organisation for Animal Health. After more than thirty years of existence in the scientific literature, these organisms still pose questions and research challenges to investigators. This paper reviews current knowledge of the group and key references. The review was focused on taxonomy, epidemiology, pathology and potential control methods for these organisms in order to enhance understanding of paramyxean infection issues in mollusc aquaculture.Key words: Taxonomy / Epidemiology / Pathology / Diagnosis / Paramyxean parasites Résumé -Marteiliose des mollusques : une synthèse. Au nombre des agents pathogènes des mollusques, les paramyxéens, notamment les agents appartenant aux genres Marteilia et Marteilioides, sont des protistes parasites des plus importants. Marteilia refringens et M. sydneyi constituent un souci majeur compte tenu de leur impact potentiel sur la conchyliculture dans le monde. La maladie des Abers et la maladie du Queensland (QX) sont actuellement répertoriées par l'Office International des Epizooties. Après plus de trente années d'existence dans la littérature scientifique, ces organismes posent encore questions et défis aux investigateurs. Cet article fait l'état des connaissances sur le sujet en s'attachant plus particulièrement à la taxonomie, l'épidémiologie, la pathologie et les méthodes potentielles de contrôle de ces organismes dans l'optique d'une meilleure compréhension de la problématique des paramyxéens en conchyliculture.