Microfilaria survey methods and analysis of survey data in filariasis control programmes.

Based on studies carried out by the author and his associates in areas of Japan and South Asia where malayan and bancroftian filariasis is endemic, this paper recommends methods for use in microfilaria surveys and in the analysis of data obtained in such surveys. The author recommends the use of measured blood samples of 30 mm(3), with which 3 linear smears are made on slides. The blood films are then stained with azure II and eosin. Microfilarial counts made with such smears are, it is claimed, simpler, less expensive, and more reliable than those made with round, thick smears. Furthermore, the use of 3 smears from each person permits the calculation of correction factors, by means of which the detection rates that would be obtained by the use of different volumes of blood may be calculated.Information obtained by the use of this method has proved to be of great use in epidemiological studies of filariasis in endemic areas, in comparing the prevalence of the disease in different populations, and in evaluating the results of control measures. Different ways of recording and classifying the results are described, and the frequency distribution of microfilarial densities is analysed.