The parasite of the week is a very small (7-15 μm long) but worldwide occurring unicellular parasitic flagellate from the class of Kinetoplastea, which is called Ichthyobodo necator. It causes the disease known as Ichthyobodosis. Ichthyobodosis affects fish both in their natural habitat as well as in aquaculture, and can be the cause of large numbers of fatalities. Ichthyobodo necator is infectious within a wide temperature range, from +2 °C for carp in ponds to more than +30 °C for fish in tropical aquariums. Ichthyobodo will even stay active and viable at temperatures of +38 °C.
The parasite attacks both the skin and gills of fish. On the body surface of infected fish, a gray-white coating is noticeable caused by excessive mucus secretion. Fish become “depressed”, start to swim and hover near the surface of the water or at the bottom of the aquarium with their fins pressed against their body, making slight oscillatory movements, mainly rocking left and right. Gill damage develops, resulting in respiratory distress. In severe cases, skin necrosis and rejection of the epithelium of the skin can be observed. Ichthyobodo necator feeds directly on epithelial cells by a cytopharyngeal canal that protrudes into the host cell, thus destroying the gill and skin epithelium.
For an accurate determination of Ichthyobodosis, it is recommended to conduct a microscopic examination of skin scrapings or gill samples. Keep in mind that parasites quickly disappear from dead or even dying fish, therefore, it is best to take samples from sick but viable fish. In tissue samples, parasites can be seen moving freely or being attached to epithelial cells. The shape of Ichthyobodo necator resembles a “comma”, they move in a characteristic oscillating and rotating fashion, which enables you to accurately identify the parasite. Once the diagnosis of Ichthyobodosis is confirmed, treatment of your fish should be started immediately, as the sooner the disease is recognized and treated, the greater the chance of success.