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PubMed2004

[Diagnostic kits in parasitology: which controls?].

The development of new diagnostic tools particularly for some parasitic "neglected diseases", is slowed or even hindered by limited resources assigned for basic and applied research in public institution and private sector. Even if the time-line and costs needed for developing a new In Vitro Diagnostic (IVD) test are generally lower compared to vaccines or new drugs, industry is poorly engaged in investing resources due to the perception of limited markets. To accelerate the development of diagnostics for the world's most deadly diseases, the World Health Organization's (WHO) Special Programme for Research and Training in Tropical Diseases (TDR), the United Nations Development Programme, the World Bank and the Gates Foundation, last year launched a new initiative, FIND (Foundation for Innovative New Diagnostics, www.finddiagnostics.org). The aim is to "apply the latest biotechnology innovations to develop and validate affordable diagnostic tests for diseases of the developing world". Ideally, a new diagnostic test should be accurately evaluated prior to use in medical practice. The first step would be a pre-clinical evaluation, an analytic study to determine its laboratory performance. A crucial point in this phase is the calibration of reagents (antigens, antibodies, DNA probes, etc.) against a standard reference preparation. WHO, through the WHO International Laboratories for Biological Standards, "provides International Biological Reference Preparations which serve as reference sources of defined biological activity expressed in an internationally agreed unit" (www.who.int/biologicals/IBRP/index.htm). Standardization allows "comparison of biological measurements worldwide" and ensures the reliability of diagnostic procedures. These preparations are generally intended for use in the characterization of the activity of secondary reference preparations (regional, national or in-house working standards). Unfortunately, international reference standards for parasitic diseases are not available at present, except for Toxoplasma antibodies. The first international standard reagent for Anti-Toxoplasma Serum was established in 1968 and at present, an international standard reference serum, Anti-toxoplasma serum, human TOXM is available at the National Institute for Biological Standards and Control (NIBSC) in UK. Several collaborative, multicenter studies were carried out to assess the performance of different methods and commercial tests for the diagnosis of toxoplasmosis, by providing to participating laboratories a panel of well-defined sera to be tested. A four-phase process following well-accepted methodological standards for the development of diagnostics, analogous to those internationally accepted for drugs and vaccines was recently proposed. The pre-clinical evaluation, the analytic study to assess sensitivity, specificity, predictive values in laboratory (phase I), should be followed by a proof of principle study to distinguish diseased from healthy persons in easily accessible populations (phase II). The evaluation of test performance in populations of intended use (phase III), and finally the delineation of cost-effectiveness and societal impact of new tests in comparison with existing tools (phase IV) should complete the validation procedure. In this context, national regulatory agencies play a major role in pre-market approval and post-market surveillance of IVDs. The European Community in 1998 approved a directive (Directive 98/79/EC) which rules the marketing of IVD medical devices, in order to harmonise the performance levels and standards in European countries. But, among IVDs for parasitic diseases, only those to detect congenital toxoplasmosis are submitted to defined procedures to provide the verification of products before their placing on the market and the surveillance after their marketing by a notified body, which perform appropriate examinations, tests and inspections to production facilities to verify if the device meets the requirements of the directive. In U.S.A., the Food and Drug Administration (FDA), through the Office of In Vitro Diagnostic Device Evaluation and Safety (OIVD), provides a comprehensive and regulatory activity for IVDs through pre-market evaluation and post-market surveillance. In developing countries, the scarcity of resources limits the procedures through which the national control authority can assure safety, quality and efficacy of products marketed, both imported and locally manufactured.

Animals↗
PubMed2005

Geographical Information Systems in parasitology: a review of potential applications using the example of animal trypanosomosis in West Africa.

The epidemiology of vector-borne diseases is complex due to the variability in the ecology of the different actors involved, i.e. hosts, parasites and vectors. The transmission of African animal trypanosomosis in the West-African savannah region is an excellent example of this complexity: riverine tsetse flies have an heterogeneous distribution along the rivers, depending of suitable habitats, and transmit pathogenic trypanosomes were they use domestic animal as feeding hosts. Contrasting epidemiological situations may thus occur at the local scale, and a broad view of the overall environment is necessary to quantify the interfaces in time and space between hosts and vectors. Geographical Information Systems (GIS) can provide new insight into the study of such complex epidemiological processes. GIS is a powerful technology that has been used mainly in map-making, and an enormous amount of knowledge can be gained simply by geographical data projection. GIS also allows juxtaposition of different types of information, creation of new variables, testing of theories and correlation, and generating of predictive models. The purpose of the present paper is to exemplify the potential application of GIS using a recent study carried out on animal trypanosomosis in a cattle-raising area of Burkina Faso.

Africa, Western↗