Martin, just as a quick and "unreflected" answer [admitting not to have done either research on Nosema sp. ('microsporidian' parasites), or as you requested, staining such spores/parasites for their protein content]:

perhaps see: Thesis of YAN PENG - ‎2014 @ http://research-repository.uwa.edu.au/files/5296503/Peng_Yan_2014.pdf;

McGOWAN et al, 2016 @ https://www.ncbi.nlm.nih.gov/pubmed/27693753 ;

or: http://www.istic.ac.cn/suoguan/detailed.htm?dbname=zw_qk&wid=0120130101408609 (" Detection and identification of Nosema ceranae by dual fluorescent staining with Calcofluor White M2R and Sytox Green%Calcofluor White M2R与Sytox Green双重染色法鉴别蜜蜂微孢子虫 " Chinese, but: "Nosema ceranae is a microsporidian parasite of Apis cerana, Apis mellifera and bumblebees that has an adverse effect on pollination, especially of fruits and vegetables, and apiculture. In this study, Calcofluor White M2R and Sytox Green stains were used to discriminate between live and dead N. ceranae. The results show that dead N. ceranae spores had yellow-green fluorescence whereas live spores fluoresced white - blue. This method allows easy detection and identification of live and dead N, ceranae and should therefore contribute to further research on TV. ceranae and its treatment. "

or: http://www.istic.ac.cn/suoguan/detailed.htm?dbname=zw_qk&wid=0120111203035719 (Chinese, but: " .... the morphological observation of Nosema bombycis in drosophila body fluid was also analyzed by calcofluor white M2R fluorescent staining. "

Last but not least (these forementioned references might not be the least one) you could search Google or Scholar google for | "stain*, staining AND microsporidia | and another resource most obviously is to be found already on ResearchGate::

https://www.researchgate.net/post/What_is_the_best_stain_for_microsporidia.

Best of luck and wishes!