Cryptosporidium oocysts and Giardia cysts—A practical and sensitive method for counting and manipulating small numbers

Abstract A rapid and inexpensive method is described for accurate and reproducible counting and manipulating small numbers of Cryptosporidium oocysts and Giardia cysts. From a suspension of oocysts or cysts at concentration from 1000 to 5000/mL (1–5/μL), replicate 5 μL droplets are micro pipetted onto the edge of a microscope slide. Unstained oocysts or cysts in each droplet can be counted in a few minutes and replicated for statistical strength. The concentration of the suspension can then be verified by pipetting desired volumes containing approximately desired numbers onto confined 13 mm membranes for IFA staining and counting with replication as desired. Requiring only a micropipette, analytical balance, and a microscope, this provides a useful tool accessible to virtually any microbiology laboratory.