Comparison of thick blood smear and saponin haemolysis for the detection of Loa loa and Mansonella perstans infections.

In an endemic area, Loa loa and Mansonella perstans microfilariae were detected by the examination of 5 ml blood in respectively 7.4 and 26.2% of subjects who would have been erroneously considered amicrofilaraemic by the conventional method of two thick blood smears (40 microliters blood). Correction factors to be applied to the results obtained with thick blood films in order to approach the true parasitological prevalences were 1.5 for L. loa and 1.6 for M. perstans. In addition, the analysis of a large volume of blood provides a better estimation of microfilarial load of the parasitized population.