Causes of head perforation triggered by Spironucleus infections in fish

Signs of infection by Hexamita sp., Octomitus sp. - and Spironucleus sp.): affected fish first lose their appetite, then their colors darken, and they begin to swim unsteadily. Especially in discus, and sometimes in other fish, small holes appear on the head, parasites protrude from the holes like whitish material, and parasites can also be found in fresh excrement. As the disease progresses, the fish become emaciated, and the small holes enlarge as the flesh is eaten away.

Among affected fish, discus are the most feared for developing this disease, the so-called "head perforation" disease, or discus disease, which may also have other unidentified causes. In particular, it may appear in the same way in large angelfish and gouramis.

Infection details: Both Hexamita and Spironucleus sp. are visible under the microscope, single-celled parasites with eight flagella, and Spironucleus sp. is rounder in shape than Hexamita and not as slender. The two parasites have similar lifestyles, but Spironucleus sp. is usually less debilitating. Little is known about the reproductive cycle of these parasites. However, under crowded environmental conditions, the parasites may be introduced with food and spread. They reproduce in the intestine and spread through the blood to all the internal organs of the body. Heavily affected fish may become emaciated and die without showing any external damage. This situation is especially common in young cichlids and gouramis. Wounds on discus and other fish very quickly suffer secondary infections caused by fungi and bacteria.

Recommended treatments include agents specifically for treating Hexamita, but certain newer antiparasitic compounds are effective. This disease responds to metronidazole and dimetridazole administered through food and water (must be a veterinary formulation). Success requires ensuring early treatment and using suitable antifungal and antibacterial medications to resolve the secondary infections.