A unique human phage display library was used to successfully generate a scFv to the highly carcinogenic toxin aflatoxin B1. Such an antibody has major potential applications in therapy and diagnostics. To further exploit its analytical capacity, the scFv was genetically fused to alkaline phosphatase, thereby generating a novel and highly sensitive self-indicating reagent. The performance of this reagent was further characterized, demonstrating its efficacy. The sensitivity of scFv-AP fusion was three-fold better than that of the scFv form. The ability of this human library to generate antibodies to a small hapten was clearly demonstrated and this is linked to its intrinsic diversity, which exceeds many existing conventional human libraries. Our results indicate that demography may influence the diversity of the repertoire of the library in terms of its capacity to generate antibodies to specific targets. Equally, the approach demonstrated should also be applicable for other haptens and larger antigens.