Review of freshwater crayfish viral disease

Disease agents and pests associated with freshwater crayfish fall into seven main categories - viruses, bacteria,rickettsia-like organisms, fungi, protists and metazoans. Data and information on specific disease agents and pests from each of these categories are presented in this review. Each agent or group of agents is considered under seven headings - condition, causative agents(s), epizootiology, diagnosis, transmission and viability, remarks for risk assessment and references. Information for the review was obtained from the published literature and from personal contact with internationally recognised experts in freshwater crayfish aquaculture, biology and disease.A total of ۳۸ different organisms or groups of organisms has been reviewed and data of relevance for import risk analysis summarized.Viruses comprise a conspicuously understudied group of freshwater crayfish pathogens. In fact, the first natural viral infection of a freshwater crayfish was described only several years ago. Since this discovery, a further fournew freshwater crayfish viruses have been reported and there have been descriptions of viruses important in other aquaculture industries experimentally or naturally infecting freshwater crayfish species. Generally, the viruses found only in freshwater crayfish have not been studied beyond preliminary descriptions of their morphology.However, in some cases their morphogenesis, and in fewer cases, their nucleic acid composition, has been described. No freshwater crayfish virus has been purified to compare physicochemical characteristics with other viruses or to produce highly specific and sensitive molecular diagnostic tools. Therefore, much of the specific information required for the purposes of preparing an import risk assessment (IRA) is not yet available. Infectious pancreatic necrosis virus (IPNV) causes acute disease in salmonids. Consequently, IPN disease and virus viability was thoroughly reviewed in preparing the IRA for salmonids (DPIE ۱۹۹۷). Therefore, this review will be limited to information relevant to the virus in crayfish. Information for the IRA of freshwater crayfish product will be taken from both this review and the salmoniformes review. IPNV-infected A. astacus do not exhibit clinical disease. However, IPNV can be isolated from A. astacus haemolymph up to ۱ yr post experimental inoculation (injection, oral and water borne exposure).

Keywords:

freshwater , crayfish , viral disease , IPNV