Ichthyophoniasis
The Ichthyophoniasis is a systemic mycosis mainly in salt water fish, in some cases also freshwater fish, occurs. In both cases it can lead to high losses among the infected animals. Because of the similarity of the histological changes, the diagnosis can be confused with fish tuberculosis .
Pathogen
The trigger is probably the fungus Ichthyosporidium hoferi or several closely related pathogens. In general, I. hoferi is assigned to the egg fungus, but it has not yet been conclusively clarified whether it is really a fungus.
The Atlantic herring is particularly susceptible to infections . Epidemics occur regularly on the North American east coast, especially in winter and spring . A variety of other marine fish can also be infested. Diseases of freshwater fish are mainly attributed to infected food, but copepods are also discussed as a possible source of infection.
Symptoms
Basically, the symptoms are very similar to those of fish tuberculosis. In organs and muscles there are granulomas encapsulated with connective tissue , the so-called spores, up to a size of 250 μm. Concomitant symptoms are emaciation, "bulging eyes", skin ulcers and ascites . In the case of very susceptible herring, a “sandpaper effect” of the skin occurs, especially on the sides, due to the formation of pods. The disease is chronic.
Diagnosis and therapy
The diagnosis is made on the basis of the histological changes, with the germination stages of the spores in particular enabling reliable detection.
An effective treatment is currently not known. Infested animals can only be killed and the housing conditions improved. In order to avoid the introduction into fish farms, unsterilized fish waste must never be fed.
Danger to people
A risk of infection for humans through Ichthyosporidium hoferi is not likely. The meat of infected fish gives off an unpleasant odor and should not be eaten.
literature
- Rudolf W. Hoffmann: Fischkrankheiten , Eugen Ulmer KG, Stuttgart 2005, ISBN 3-8252-8241-4
