The OV16 antigen, localizes to the hypodermis, cuticle, and uterus of female O. volvulus is regarded as a highly sensitive and specific antigen for detection of IgG4 in people with prior exposure to onchocerciasis. It has an open reading frame that encodes a 152- amino acid polypeptide containing a 16-amino acid putative signal peptide. Enzyme-linked Immunosorbent Assay serological testing of OV-16 antigen is a diagnostic tool for determining effective elimination of the parasite.