Onchocerca volvulus: Genetic diversity of parasite isolates from Sudan

Onchocerciasis in Sudan exists in three distinct foci which exhibit differi ng clinical presentations. Previous studies have demonstrated that a tandem ly repeated Onchocerca sequence family with a unit repeat length of 150 bp (the O-150 family) is a useful marker for deducing relationships among diff erent O. volvulus populations. In the current study, the O-150 repeat famil ies of O. volvulus from Sudan were analyzed and compared to each other and to those of parasites from West Africa. Similar to West African and America n O. volvulus, the O-150 families of the Sudanese parasites could be divide d into clusters within which little or no intracluster variation was eviden t, suggesting that the O-150 family in these parasites was subject to the f orces of concerted evolution. Statistical analysis of the O-150 families fr om the different Sudanese parasite isolates, employing a nested algorithm b ased on an analysis of variance, revealed that O. volvulus endemic to the n orthern focus at Abu Hamed were significantly different from all other O. v olvulus populations examined to date. In contrast, parasites from the south ern and eastern foci of Sudan were indistinguishable from those endemic to the West African savanna. The significance of these data are discussed in l ight of knowledge of the biogeography and biology of transmission of O. vol vulus in Africa. (C) 2001 Academic Press.