This week we will talk about the unicellular parasite Spironucleus sp. that causes the infamous hole in the head disease, also known as Spironucleosis, which is dangerous for aquarium fish. Spironucleosis is caused by unicellular flagellated microorganisms of the family Diplomonadidae, named Spironucleus sp.. In the past Spironucleus was confused with Hexamita and Octomitus, and most aquarium literature still attributes hole in the head disease to Hexamita or sometimes Octomitus.
Infestation of the intestinal mucosa by Spironucleus vortens, leads to systemic infection in ornamental fish. Symptoms are, loss of appetite and weight, discharge of white stringy feces, destruction of epidermal tissue with the formation of erosions(holes) on the head and body, mainly in the area of the seismosensory system. Besides holes in the head, fish can have one-sided popeye disease (unilateral exophthalmia of the eyes), bloating (concurrent abdominal distension), lethargy and often extremely high mortality. Necropsy may show hemorrhages, peritonitis, catarrhal inflammations of the intestinal mucous membrane with exudate accumulations. Holes in the head and white stringy feces are the main signs most people will recognize when the fish have Spironucleosis.
Many aquarists who keep cichlid fish (angel fish / Pterophylum scalare, discus / Symphysodon discus, Oscars / Astronotus ocellatus, Dwarf cichlids like apistogramma, etc.), are familiar with this problem firsthand. However, Spironucleus sp. can affect other groups of fish – such as catfish, barbs, gourami and even neon tetra can be carriers of these parasites. Parasites spread in the aquarium through the feces of infected fish, and these parasites can survive without a host for more than 36 days, infecting the other fish directly, without the need for intermediate hosts. In small numbers, flagellates can be present in the intestines of many fish without causing any problems or disease. This condition is called endocommensalism. However, a deterioration of living conditions (such as an increase of nitrates, phosphates or organic waste), transport of fish, lack of nutrients, overcrowding or other stress factors that affect the immune system, can cause an outbreak of parasites and diseases.
Microscopic diagnosis of fish feces can help to determine whether the fish are indeed infected with intestinal flagellates. If you buy new fish, try to quarantine them, and if you notice symptoms of this disease in your fish, we recommend a treatment with eSHa HEXAMITA, which was specifically made to combat Spironucleosis and related symptoms in fish.