The species of this group of pathogens are obligate intracellular parasites with unicellular spores, single tubular polar filaments and without mitochondria. Molecular studies have shown that the group is related to the fungi and it is often placed within the kingdom of fungi. Microsporidia infect a large variety of organisms including arthropods, vertebrates and other groups. In insects, the infections are initiated through the gut wall. Although they are typically slow acting, they can cause significant mortality and are of interest as biological control agents.
This page covers microsporidian diseases of pest species only. For species harmful to beneficial insects like honey bees see the section on Microsporidia (of beneficial insects).
The following families are currently in the system: