Sensitive and specific serodiagnosis of river blindness using Onchocerca ochengi antigens

Despite the large-scale application of ivermectin for the treatment of human onchocerciasis, this filarial disease has remained a public health hazard, requiring rapid and sensitive diagnostic methods for more efficient management. Several serological methods based on homologous native or recombinant diagnostic antigens have been developed. However, these antigens have remained scarce in the endemic areas. We report herein the preparation and evaluation of an Onchocerca ochengi total worm extract together with its low molecular weight (< 31 kDa) and 14.4 kDa antigens for the diagnosis of human onchocerciasis. The 14.4 kDa antigen and the low molecular weight antigen fraction were identified by Western blot experiments. The antigens were employed for the detection of IgG4 in sera of 43 onchocerciasis patients, 35 normal Africans, 15 schistosomiasis patients, 11 ascariasis patients, 9 loaisis patients and 3 healthy Europeans. The diagnostic specificity values were 94.5, 87.5 and 100%, while the sensitivities were 90.7, 80 and 76.6% using the worm extract, low molecular weight antigen fraction and the 14.4 kDa antigen, respectively. We conclude that total worm extracts of O. ochengi can conveniently replace recombinant antigen cocktails in poor settings that do not have access to the latter.