Thelohanellus kitauei is a freshwater myxozoan parasite (family Myxobolidae) infecting the intestinal wall of common carp (Cyprinus carpio) in East Asia, causing intestinal thelohanellosis characterized by large, visible cysts in the gut wall that cause significant morbidity and mortality in infected fish, particularly in Chinese and Japanese carp aquaculture. Its genome revealed extensive gene loss and metabolic pathway reduction consistent with obligate intracellular parasitism.