WUCHERERIA-BANCROFTI IN TANZANIA - MICROFILARIAL PERIODICITY AND EFFECT OF BLOOD-SAMPLING TIME ON MICROFILARIAL INTENSITIES

The circadian periodicity of Wuchereria bancrofti microfilarial (mf) i ntensities in peripheral blood was analysed in a group of infected ind ividuals from an endemic community in north-eastern Tanzania. The mf d ensity was quantified at two-hourly intervals for 24 hours. A clear no cturnal periodic pattern was observed. Mathematical analysis of the da ta indicated a peak at 0152 h and a periodicity index of 117.5. A peri odicity equation was developed describing the average relation between mf intensity and hour of the day for the study area. Based on the obs erved periodicity pattern, the effect of blood sampling before peak ti me is discussed, and the importance of taking sampling time into consi deration when analysing data from epidemiological studies is emphasize d. A simple method is devised which can be used to adjust for the infl uence of time on mf intensities, in studies where accurate information on mf intensities is necessary, and where it is impossible to obtain all samples at peak time.