These parasites primarily infect invertebrates. Spores are eaten, and within minutes their polar filaments penetrate the intestinal epithelium of the host. The sporoplasm travels through the polar filament to enter the host cell, and becomes a trophozoite. During the next week the trophozoites undergo two rounds of schizogony. After the second round they produce a large number of spores. These rupture the host cell and pass in the host's feces. Damage to the host's intestine is extensive and mortality is common.