Quantitative aspects of the infection of Simulium ochraceum by Onchocerca volvulus: the relation of skin microfilarial density to vector infection
Campbell, C.C.; Collins, R.C.; Huong, A.Y.; Marroquin, H.F.
Tropenmedizin und Parasitologie 31(4): 475-478
1980
ISSN/ISBN: 0303-4208 PMID: 7233543 Document Number: 167050
In Guatemala, 16 wild adults of Simulium ochraceum Wlk. were permitted to feed on a 15 X 15-in. grid delineated on the back of each of 13 persons infected with Onchocerca volvulus. Based on 6 skin biopsies, the mean microfilarial density in these study participants ranged from 1.256 to 111.824 microfilariae/mg of skin. The flies were dissected 6-10 h after feeding and the number of microfilariae in the blood-meal and escaping from the mid-gut into the thoracic musculature were counted. An almost linear relationship was found between the mean skin microfilarial density and the mean microfilarial uptake by S. ochraceum. An even stronger relationship existed between the mean microfilarial density and the mean number of microfilariae escaping from the mid-gut. Since the approximate 1:1 ratio observed between the number of microfilariae escaping from the mid-gut and the subsequent number of infective (third-stage) larvae had been previously demonstrated, it could be concluded that a similar linear relationship exists between microfilarial skin densities and the number of third-stage larvae available for transmission of O. volvulus by the Guatemalan vector.