Revue Scientifique et Technique-Office International Des Epizooties最新文献

The availability of rapid, highly sensitive and specific molecular and serologic diagnostic assays, such as competitive enzyme-linked immunosorbent assay (cELISA), has expedited the diagnosis of emerging transboundary animal diseases, including bluetongue (BT) and African horse sickness (AHS), and facilitated more thorough characterisation of their epidemiology. The development of assays based on real-time, reverse-transcription polymerase chain reaction (RT-PCR) to detect and identify the numerous serotypes of BT virus (BTV) and AHS virus (AHSV) has aided in-depth studies of the epidemiology of BTV infection in California and AHSV infection in South Africa. The subsequent evaluation of pan-serotype, real-time, RT-PCR-positive samples through the use of serotype-specific RT-PCR assays allows the rapid identification of virus serotypes, reducing the need for expensive and time-consuming conventional methods, such as virus isolation and serotype-specific virus neutralisation assays. These molecular assays and cELISA platforms provide tools that have enhanced epidemiologic surveillance strategies and improved our understanding of potentially altered Culicoides midge behaviour when infected with BTV. They have also supported the detection of subclinical AHSV infection of vaccinated horses in South Africa. Moreover, in conjunction with whole genome sequence analysis, these tests have clarified that the mechanism behind recent outbreaks of AHS in the AHS-controlled area of South Africa was the result of the reversion to virulence and/or genome reassortment of live attenuated vaccine viruses. This review focuses on the use of contemporary molecular diagnostic assays in the context of recent epidemiologic studies and explores their advantages over historic virus isolation and serologic techniques.

Any modification to a validated assay must be evaluated in terms of the impact on the assay's performance characteristics and whether the assay remains fit for the intended purpose. The comparison is referred to as a 'method comparison', 'method comparability', 'method change', or 'comparative validation'. This review presents recommendations and examples of studies found in the current literature as a means of assessing minor modifications. In addition, the authors discuss common statistical approaches used for these comparisons.

To provide a standardised approach to the diagnosis of diseases and to facilitate health certification for trade, the World Organisation for Animal Health (OIE) standards, described in the Manual of Diagnostic Tests and Vaccines for Terrestrial Animals (Terrestrial Manual), include internationally agreed laboratory diagnostic techniques. This review examines the type of tests recommended in the disease-specific chapters of the Terrestrial Manual for the six most common purposes of diagnostic techniques, including certification for movement, confirmation of clinical cases and disease surveillance. The most frequently recommended tests for all six purposes are enzyme-linked immunosorbent assay and/or polymerase chain reaction, for which there are detailed validation guidelines in the OIE Terrestrial Manual. This is true for all species and no species-specific barriers to validation related to test type were identified. Classical techniques continue to be well represented in the Terrestrial Manual recommendations whereas novel technologies are slow to gain acceptance. These classical tests can present challenges for validation as there may be a dearth of international standard reagents and harmonised protocols.

Analytical characteristics of diagnostic tests, encompassing estimates of repeatability, analytical specificity (ASp) and analytical sensitivity (ASe), are determined during Stage 1 of the OIE Assay Validation Pathway. Repeatability (an estimate of assay precision and robustness), ASp (measuring only what an assay is intended to measure) and ASe (synonymous with the lower limit of detection) are fundamental parameters that determine future test performance. Importantly, these parameters provide the basis for deciding whether a prototype assay progresses to the next stage of the OIE Assay Validation Pathway (determination of diagnostic characteristics) or is withdrawn in favour of alternate tests with better analytical performance characteristics. Implicit in the successful development and validation of any assay is a sound understanding of the target pathogen, the disease pathogenesis in susceptible hosts, the fundamental technical principles that underliey each test system, and its intended use. Factors that affect analytical characteristics of diagnostic assays are numerous and may vary according to each assay type. Using, as examples, development of an enzyme-linked immunosorbent assay for detection of antibodies to capripoxviruses, and the comparative assessment of three quantitative real-time polymerase chain reactions for detection of African swine fever virus DNA, the main factors affecting analytical characteristics of serological and molecular assays are considered. As reviewed within, comprehensive and well-designed experiments are required to develop and optimise assays with favourable analytical characteristics. The underlying principles are broadly applicable to all assay types and, when conducted with appropriate rigour, provide the foundations for high-quality diagnostic tests that are fit for their intended purpose(s).

In this paper, the authors: (a) list methods used to diagnose zoonotic diseases in humans and animals; (b) identify between-species differences in diagnostic approaches, providing commentary on the benefits that might arise from simultaneous interpretation of data from human and animal health surveillance systems; and (c) reiterate the importance of using species-specific, validated diagnostic tests for surveillance and disease outbreak investigations. Emerging and endemic zoonotic diseases are likely to provide a continued threat to global health in the short- to medium-term future. A good deal of knowledge about the drivers of infectious disease emergence has been developed based on numerous examples from the recent past. Sharing of diagnostic resources across human and animal health sectors, sharing of human and animal health surveillance data, development of skills in the interpretation of that data and awareness of issues related to the validation and interpretation of diagnostic test data are necessary prerequisites for an effective endemic disease surveillance system. A good understanding of the epidemiological patterns of endemic disease will allow human and animal health professionals be able to more quickly detect the presence of emerging disease threats.

The World Organisation for Animal Health (OIE) Manual of Diagnostic Tests and Vaccines for Terrestrial Animals describes a diverse array of assays that can be used to detect, characterise and monitor the presence of infectious agents of farmed livestock. These methods have been developed in different laboratories, at different times, and often include tests or kits provided by the commercial sector. Reference panels are essential tools that can be used during assay development and in validation exercises to compare the performance of these varied (and sometimes competing) diagnostic technologies. World Organisation for Animal Health Reference Laboratories already provide approved international standard reagents to help calibrate diagnostic tests for a range of diseases, but there remain important gaps in their availability for comparative purposes and the calibration of test results across different laboratories. Using foot and mouth disease (FMD) as an example, this review highlights four specific areas where new reference reagents are required. These are to: reduce bias in estimates of the diagnostic sensitivity and inter-serotypic specificity of tests used to detect diverse strains of FMD virus (FMDV), provide bio-safe positive controls for new point-of-care test formats that can be deployed outside high containment, harmonise FMDV antigens for post-vaccination serology, and address inter-laboratory differences in serological assays used to measure virus-specific FMD antibody responses. Since there are often limited resources to prepare and distribute these materials, sustainable progress in this arena will only be achievable if there is consensus and coordination of these activities among OIE Reference Laboratories.

A reliable laboratory assay is an essential tool for the diagnosis or surveillance of most animal diseases. Before routine use, assays should be appropriately validated to ensure that they have performance characteristics that provide reliable results and can be used for the intended purpose. It is inevitable that, over time, changes will need to be made to assay reagents, to the assay format, to test a different species or for implementation in a new laboratory. Whenever there is a change (whether it be components, application or location), it is essential to establish whether the new circumstances affect the biological basis and properties of the assay. If the modifications do not affect the biological basis of the assay, the changes might be considered minor and a verification study can be conducted to confirm that the performance characteristics have not been adversely affected. Major changes require a new validation to be carried out. A method comparability study, where original and modified assays are run concurrently to test the same sample panel, provides an extremely robust comparison. However, comparability studies are not always an option, especially for the introduction of a method to a new laboratory. Access to original validation data and suitable reference sample panels then becomes essential to provide evidence that the assay remains 'fit for the intended purpose'.

Biobanks represent a valuable resource in many areas of biomedical research and development. They function as repositories for well-documented and well-characterised biological material that can be used as the basis for this work. Virtual biobanks amplify the availability of this resource by linking multiple biobanks via a single interface. Test development and validation is an essential process that helps to provide confidence in diagnostic test results and, by extension, the disease and health status of animal populations demonstrated by such results. The quality of the development and validation pathway can be enhanced by the use of well-characterised material for standards and validation panels. Virtual biobanks represent a powerful mechanism for enhancing access to such material, and allow other parties to both have greater confidence in the work done, and to be able to repeat it themselves, as required.

In the field of diagnostic test validation, World Organisation for Animal Health (OIE) Reference Laboratories (RLs) have a pivotal role and provide the international community with impartial advice and support in the selection, development and validation of diagnostic tests, which can be applied to the specialist diseases for which they are designated. National RLs provide an invaluable function in supporting the introduction, ongoing validation and application of validated diagnostic tests in line with international standards. Experienced staff with extensive knowledge of such systems and access to specialist facilities for conducting work are available to monitor changes or advancements in technology. They consider their relevance and value to evolving diagnostic test requirements. Reference Laboratories often have a broad mandate of activity linking research or development programmes and surveillance activities to benefit the continual assessment and, if necessary, improvement of diagnostic tools. Reference Laboratories maintain or have access to unique biological archives (known positive and negative sample populations) and produce international reference standards, both of which are vital in establishing the necessary and detailed validation of any diagnostic test. Reference Laboratories act either singularly or in collaborative partnerships with other RLs or science institutes, but also, when required, and with impartiality, with the commercial sector, to ensure new tests are validated according to OIE standards. They promote and apply formal programmes of quality assurance (including proficiency testing programmes) for newly validated tests, ensuring ongoing monitoring and compliance with standards, or as required set out any limitations or uncertainties. Reference Laboratories publish information on test validation in the scientific literature and on relevant websites, as well as disseminating information at workshops and international conferences. Furthermore, they can offer training in the processes and systems underpinning test validation.