A standardization of microfilarial densities for epidemiological comparisons in periodic bancroftian filariasis.

Microfilarial density in the peripheral blood changes with time. The average concentration in a population can only be calculated if the influence of circadian periodicity is eliminated from individual measurements. A transformation of the harmonic wave formula, describing the time dependent changes in density allows to calculate the number of microfilariae at the peak of the curve from the number observed at the time of examination. The equation was tested for strains of Wuchereria bancrofti from Liberia.