title: Longitudinal studies of skin microfilaria and antibody conversion rates in children living in an endemic focus of onchocerciasis in Nigeria.
abstract: We monitored skin microfilarial conversion and antibody (serum) conversion rates to Onchocerca volvulus recombinant antigens (OC3.6 and OC9.3) over a 2-year period, in a cohort of 208 children aged 9-11 years and living in a mesoendemic focus of savannah-type onchocerciasis in Nigeria in order to detect prepatent onchocerciasis in children. Between time point A and time point B (9 months apart) the seroconversion rate was 19.4 per cent, and between time points B and C (15 months apart), a further 31.4 per cent of seronegative children had seroconverted. However, only a third of the seroconverted children became microfilaria-positive. From the time-lag between antibody conversion and skin snip conversion, we estimated that a 9-12 month interval was required for the detection of O. volvulus microfilariae following infection with viable third stage larva (L3s). The predictive value of antibody detection as a measure of skin microfilarial conversion was >90 per cent when the optical density (OD) at 490 nm was >0.80. We therefore propose a strategy for monitoring changes in transmission of onchocerciasis following vector control or chemotherapy through an evaluation of annual antibody seroconversion rates in a standardized sentinel population of children.
authors.affiliation: Department of Biochemistry, University of the Witwatersrand, Johannesburg, South Africa.
authors.forename: A F
authors.initials: AF
authors.lastname: Ogunrinade
authors.forename: S O
authors.initials: SO
authors.lastname: Awolola
authors.forename: O
authors.initials: O
authors.lastname: Rotimi
authors.forename: R
authors.initials: R
authors.lastname: Chandrashekar
mesh_terms: D000818:Animals; D000909:Antibodies, Helminth / Q000097:blood*; D000947:Antigens, Helminth / Q000276:immunology; D002648:Child; D019353:Endemic Diseases; D006801:Humans; D007559:Ivermectin / Q000627:therapeutic use; D008137:Longitudinal Studies; D008842:Microfilariae / Q000276:immunology*; D009549:Nigeria / Q000453:epidemiology; D017181:Onchocerca volvulus / Q000276:immunology* / Q000302:isolation & purification; D009855:Onchocerciasis / Q000175:diagnosis* / Q000453:epidemiology / Q000517:prevention & control / Q000635:transmission; D011237:Predictive Value of Tests; D012876:Skin Diseases, Parasitic / Q000175:diagnosis* / Q000453:epidemiology
chemical_list: D000909:Antibodies, Helminth; D000947:Antigens, Helminth; D007559:Ivermectin