Average Raman spectra of both viable and neutralized oocysts are very similar with no prominent peaks unique to either sample once the background is subtracted, however, a small peak at 1211 cm -1 is present among the neutralized oocysts but not the viable ones. Some relative peak intensities are different between neautralized and viable average spectra, with peaks of 867, 943, 1005, 1086 and 1270 cm -1 more prominent for neutralized oocysts, while the peak of 1301 cm -1 is more prominent for viable oocysts. There is support in published studies that oocysts treated with formalin have their surface chemically altered and this can explain the difference in Raman spectra. We suggest more studies aimed at assessing the impact of chemicals on oocysts Raman spectra since this is an unexplored field. For example, by trapping oocysts in an LTRS instrument and exposing them to chemicals, one can measure changes and shifts of Raman peaks with time. These experiments can provide relevant information on the chemicals' mode of action on oocysts, similarly to what has been done on bacterial spores . In addition, volume mapping using confocal Raman can provide more details of how sporozoites are organized inside the oocysts.