Strain differentiation of Onchocerca volvulus from Uganda using DNA probes.

Polymerase chain reaction (PCR) combined with non-radioactive DNA hybridization was applied for the detection and characterization of a 150 bp tandem repeat of Onchocerca volvulus. DNA of worms from western Uganda was amplified and then probed with a digoxygenin-labelled oligonucleotide, specific for the forest form of O. volvulus and compared to samples from various African countries. Hybridization was only observed with PCR products from the forest in Liberia, south-eastern Ghana, Benin and southern Cameroon, but not with worms from Uganda or the savannah in Burkina Faso and northern Ghana. A nested PCR using primers derived form the forest form-specific DNA sequence confirmed these results. Morphometric studies revealed length differences between the microfilariae of Ugandan O. volvulus to those of West Africa, especially to those of the savannah in Burkina Faso. It is concluded that the forest/savannah classification of O. volvulus from West Africa is not suitable for Simulium neavei-transmitted O. volvulus from Uganda.