Tactical Research Fund - Aquatic Animal Health Subprogram: determining the susceptibility of Australian species of prawns to infectious myonecrosis
Australian prawn production at around 22 kilotonnes is valued in excess of $250 million. Clearly, the prawn fishery is an important natural resource for Australia that is also the basis for a significant export industry. In addition, prawn aquaculture is a significant industry in northern Australia and accounts for around 14% of the total volume of Australian prawn production. Infectious myonecrosis is a viral disease that has caused significant disease outbreaks and mortalities in farmed Penaeus vannamei in Brazil and South-East Asia, including Indonesia. While P. vannamei is considered the principal host, experimental infection of P. stylirostris (Pacific blue shrimp) and P. monodon (black tiger shrimp) has been reported. The susceptibility of other shrimp/prawn species is unknown. Information on the susceptibility of prawn species important to Australia, including banana prawns (Fenneropenaeus merguiensis), brown tiger prawns (P. esculentus) is lacking. This project would provide information on the susceptibility of two important species of Australian prawns to exotic IMNV. Such information is important to policy-makers, regulators and primary producers with respect to relevant biosecurity issues at all levels of government.
Final report
Aquatic Animal Health Subprogram: Development of molecular diagnostic procedures for the detection and identification of herpes-like virus of abalone (Haliotis spp.)
Currently, diagnosis of abalone ganglioneuritis associated with infection by the recently discovered herpes-like virus is dependent on visualisation of gross clinical signs at the macroscopic level, of histological lesions at the light microscopic level and of virus particles at the electron microscopic level. Thus, while detection of diseased abalone is relatively straightforward it is labour-intensive and time-consuming. The purpose of this project is to develop molecular diagnostic procedures for the rapid, sensitive and specific detection and identification of abalone herpes-like virus infections in the presence, or absence, of clinical signs. Thus potential broodstock that are apparently healthy can be screened for the presence of herpes-like virus, sub-clinical, infections prior to on-farm use.
In addition to surveillance tools for detection and identification of sub-clinical infections, better procedures/reagents for overt disease diagnosis are required. While the presence of histological lesions provides a presumptive diagnosis, the development of in situ hybridisation probe(s) and/or diagnostic antiserum for the localisation of abalone herpes-like virus within histological lesions will provide a means for definitive diagnosis to be made with increased confidence.
Furthermore, in addition to providing an enhanced capability and capacity for disease diagnosis (detection and identification of herpes-like virus), development of molecular reagents and procedures will assist future research aimed at better understanding the pathogenesis (e.g. tissue distribution of the virus, effect of host factors such as age) and epidemiology (e.g. determination of host and geographic ranges, modes of transmission) of this disease. Such knowledge is crucial for efficient management of current and future disease outbreaks.
Final report
Design standards for experimental and field studies to evaluate diagnostic accuracy of tests for infectious diseases in aquatic animals
In aquatic animals, experimental studies are often used to study the pathogenicity of an etiologic agent; to study interactions between the host, pathogen, and environment; and to evaluate the comparative performance of existing and novel diagnostics. In the latter case, specimens are sometimes collected from animals at different stages of infection post-challenge to demonstrate temporal changes in diagnostic sensitivity post-challenge. Diagnostic accuracy studies should be designed to assess a test’s fitness for a designated purpose, and the design should also inform reporting in peer-reviewed journals. Reported studies should include clear descriptions of purpose and intended application, and authors should discuss the limitations of their results in the context of other available or currently-used tests to facilitate informed decisions by end-users. In human medical research, standards exist for various aspects of diagnostic test research, including guidelines for accurate and transparent reporting and for quality assessment of methodologies in systematic reviews of diagnostic-accuracy studies. Similar standards are required for animal, including aquatic animal, research. It is anticipated that the established criteria, from human clinical research for evaluating diagnostic accuracy studies, can be adapted to develop a standardized set of criteria for the design of field and experimental studies to assess diagnostic accuracy for infectious diseases in aquatic animals.
Final report
Design and reporting quality are important parameters for assessing aquatic animal studies on diagnostic test sensitivity and specificity however standards for experimental design are lacking. As part of this study, design guidelines to improve the quality of published studies on test specificity and sensitivity on natural disease events well as experimental infectivity trials.
Thus important metrics for consideration at the design phase of diagnostic accuracy studies (DAS) include study purpose, targeted disease state (clinically diseased vs infected but apparently healthy), selection of appropriate samples and specimens, laboratory analytical methods, statistical methods and data interpretation. Implementing standards for designing DAS will assist in appropriate test selection for specific testing purposes and minimize the risk of reporting biased estimates of diagnostic sensitivity and specificity. In addition, with respect to pool-level sensitivity, using the developed protocols in DAS will ensure that the effect of pooling samples for the specified disease agents and hosts on diagnostic sensitivity will be clearly defined.