Application of a Recombinase Polymerase Amplification (RPA) assay and pilot field testing for Giardia duodenalis at Lake Albert, Uganda.

Giardia duodenalis is a common gastrointestinal protozoan causing 184 million cases of giardiasis worldwide annually. Detection is by microscopy or coproantigen assays, although diagnostic sensitivity is often compromised by intermittent shedding of cysts or trophozoites, as well as operator expertise. Therefore, for enhanced surveillance field-applicable, point-of-care (POC), molecular assays are needed. Our aims were to: 1) optimise the recombinase polymerase amplification (RPA) assay for the isothermal amplification of the G. duodenalis β-giardin gene from trophozoites and cysts, using published primer and probe sequences, and 2) perform a pilot field validation of RPA at a field station in a resource-poor setting, on DNA extracted from stool samples from schoolchildren in villages around Lake Albert, Uganda. Results were compared to an established laboratory small subunit ribosomal RNA (SSU rDNA) qPCR with additional testing using a specific assemblage qPCR targeting the triose phosphate isomerase (tpi) DNA regions that can distinguish G. duodenalis of two different assemblages (A and B), which are human specific.