Management of Hexamita in Ornamental Cichlids
Ruth Francis-Floyd and Peggy Reed May 27, 2002

Hexamita is a flagellated protozoan found in the gastrointestinal tracts of a variety of cold and warm water fish, including several species of Cichlids which are popular aquarium pets. It can be a serious health problem in angel fish and discus. Occasionally hexamita is found in healthy fish. Stress from malnutrition, shipping, over-crowding, or poor water quality may lead to rapid reproduction of the protozoan, resulting in disease.

Figure 1: Drawing of a free swimming protozoan organism known as Hexamita.

The genus hexamita was formerly called "Octomitus" because of eight hair-like flagella which project from the organism ( Figure 1 ). Three species of hexamita have been associated with disease in fish, Hexamita salmonis , Hexamita truttae and Hexamita intestinalis . It is unknown whether these species or new species which have not yet been identified are responsible for disease in ornamental fish.

Transmission of hexamita
Hexamita is probably transmitted through the water from contaminated fecal material. The flagellated stage makes its way to the lumen of the upper intestine. There it swims freely in the intestinal and cecal fluids. The organism may be present in small numbers under normal circumstances; however, for disease to develop the organism must reproduce rapidly resulting in a massive infestation. Generation time for the flagellated form is thought to be 24 hours.

Signs of hexamitiasis
Weak or stressed fishes seem to be most susceptible to heavy infestation. Physical signs of hexamitiasis include weight loss, decreased activity and refusal of food. Angel fish which are severely infected with hexamita may lie horizontally on the surface of the water with the abdomen visibly distended. Angel fish may remain in this condition for several days. These severely infested fish often recover following treatment with metronidazole. Infestations in adult breeding angel fish may be associated with decreased hatchability of eggs or death of young fry.

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