CONCENTRATION OF MICROFILARIAE OF ONCHOCERCA-VOLVULUS BY SIMULIUM-SANGUINEUM DURING FEEDING - USE IN MAPPING PARASITE DISTRIBUTION IN THE SKIN

A comparison was made between the mean number of microfilariae of Onchocerca volvulus ingested by 10 Simulium sanguineum feeding on 2 different areas of the body of 4 infected Yanomama indians and the mean number of mf/mg in 10 skin snips taken from the same areas. Between 2.3 and 28 times as many microfilariae were recovered from the midguts of the flies as were found in the skin snips. Using both methods, the distribution of microfilariae in the skin of the same indians and an additional volunteer, who had been treated 2 years previously, was determined. In both cases the highest densities of the parasite were found in the torso, with dorsal surfaces of the body and extensor surfaces of the limbs being more heavily infected than the ventral and flexor surfaces. The possibility of using S. sanguineum for the detection of low-density infections of O. volvulus is discussed.