Heterobothrium okamotoi infects the gills and branchial cavity wall of Japanese pufferfish Takifugu rubripes, feeding on blood from the gills. Infection of this monogenean can cause anemia, and adult worms on the branchial cavity wall induce inflammation and tissue necrosis by the action of haptoral clamps. Eggs deposited as a long string easily entangle on the culture net, which is prone to heavy infection of pufferfish cultured in net cages, as the oncomiracidium, hatched larva, can encounter the host fish at much higher chances than expected in natural waters. Prevention of infection is practically impossible as its life cycle has been established in culture farms. Chemotherapy with hydrogen peroxide or febantel, a benzimidazol, is effective but repeated treatment may be required, as immunity acquired by infected fish is not perfect. Biological data on H. okamotoi should be effectively incorporated in its control measures.
