Here's a really comprehensive overview of Microsporidia -- https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5613672/

Still working through this and the original paper, but while it can cause encephalitis in humans, it seems to be ubiquitous already anyway, and we don't seem to typically get it from insects. Setting aside the fact that you could swap malaria for almost any other infectious disease and humanity would be massively better off.

(Caveat: IANA Microbiologist and welcome corrections.)