Giardia spp. is an intestinal parasite responsible for worldwide disease outbreaks. Guiding researchers and practitioners to choose among current methods for microscopy detection of the infectious forms may be directly beneficial to public health and the environment. This study provides an overall comparison of brightfield (BF), fluorescence and darkfield (DF) microscopies for detecting Giardia duodenalis and Giardia muris cysts, by illustrating micrographs of such protocols applied to purified samples, as well as discussing advantages and constraints based on secondary information and collected data. BF analysis included Lugol's iodine staining. In fluorescence microscopy, samples were processed by immunofluorescence assay (IFA) with DAPI and by standalone DAPI dye. Cyst suspensions were also analysed by DF microscopy using a recently developed low-cost system. The three techniques enabled detecting Giardia spp. cysts, although they did not provide species identification by morphology. The overview of each method points out some relevant aspects to consider when selecting common optical microscopy techniques, and includes challenges and advantages regarding each of them.
This work was supported by the São Paulo Research Foundation – FAPESP (Process 12/50522-0), The Royal Society (ICA\R1\201373 – International Collaboration Awards 2020), and National Council for Scientific and Technological Development (CNPq-Brazil, process no. 308070/2021-6). The Coordination for the Improvement of Higher Education Personnel (PNPD/CAPES) awarded a fellowship to M.J.R.d.C.
© 2023 The Authors.
- Lugol's iodine
- optical microscopy
- waterborne protozoa