The differential dispersal of nulliparous and parous Simulium damnosum
Duke, B.O.
Tropenmedizin und Parasitologie 26(1): 88-97
1975
ISSN/ISBN: 0303-4208 PMID: 1145728 Document Number: 89841
Dissections of adults of Simulium damnosum Theo. caught in the Sudan-savanna zone of Cameroon on river banks or 1 or 3 km inland indicated that nulliparous females dispersed mainly inland away from their riverine breeding sites. Parous females also dispersed inland to the same distances as nulliparous ones, but mainly they stayed near, or moved along, the banks of the rivers in which breeding occurred. This tendency was most marked in the older parous females. As a result of this differential dispersal, the numbers of females of S. damnosum carrying infective larvae of Onchocerca volvulus were highest on the banks of the rivers in which breeding took place. This has an important bearing on the epidemiology of onchocerciasis. Tests at one place in the Guinea-savanna zone indicated that the dispersal pattern there was similar. In the forest zone, nulliparous females tended to stay near the rivers, and the proportions of parous and infective females were higher inland than along the river bank. Dissections of Simulium damnosum in the Sudan-savanna zone of Cameroon indicated that nulliparous flies dispersed mainly inland, away from their riverine breeding sites. Parous flies also dispersed inland to the same distance as nulliparous flies, but mainly they stayed close to, or moved along, the banks of the breeding rivers. This tendency was most marked in the older parous flies. As a result of this differential dispersal, the numbers of S. damnosum carrying infective larvae of Onchocerca volvulus were highest on the banks of breeding rivers. This has an important bearing on the epidemiology of onchocerciasis. Tests at one place in Guinea savanna indicated similar dispersal pattern there. In the forest zone nulliparous flies tended to stay near the rivers; and the proportions of parous and of infective flies were higher inland than on the river bank. [AS].