Antigen detection in onchocerciasis: correlation with worm burden.

Detection of O. volvulus antigen by indirect ELISA test in the serum and the urine of 169 individuals with residence in the southeast onchocerciasis endemic focus in Chiapas, Mexico was performed. Every individual under study was physically examined for signs of onchocerciasis in particular for subcutaneous nodules, dermic lesions, ocular damage and history of Mazzotti reaction. Of the total cases, 91.7% were positive for skin microfilariae. Only 32.2% of the microfilariae positive cases carried at least one palpable nodule. The sensitivity of the ELISA test was 92.3% for serum and 85.9% for urine. A good correlation between the transformed numbers of skin microfilariae (square root of x + 1) and the positivity of the ELISA test for serum and for urine was found. It was also observed that the ELISA test values for the sera and for the urine showed a good correlation with r = 0.76 and Z0.95 less than 0.005. This serological test can be used for seroepidemiological surveys and for orientating the activity of massive onchocerciasis treatment campaigns.