Furunculosis of the fish

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The furunculosis of the fish is at trout fishing occurring bacterial infection caused by Aeromonas salmonicida is caused. Char and brown trout are particularly hard hit . It occurs in all age groups and occurs more frequently in summer with high water temperatures, lack of oxygen, overfeeding and other stress factors. The clinical picture is very variable, eponymous was the subacute skin shape, which is accompanied by changes that are reminiscent of boils . Real boils, i.e. abscesses of the hair follicles, do not naturally occur in fish.

Pathogen and transmission

The furunculosis is caused by Aeromonas salmonicida ssp. salmonicida , a member of the genus Aeromonas . The infection occurs through direct contact with the contents of the bump, feces and urine of infected fish and indirectly through eggs, equipment, birds and blood-sucking parasites that are contaminated with the pathogen.

An analogous disease in carp is carp erythrodermatitis (CE), which is caused by a subspecies of Aeromonas salmonicida that specializes in carp . This disease was formerly known as the "ascites ulcer" and classified as part of the carp spring viremia complex .

Clinical picture

The acute form occurs mainly in juvenile fish. It is characterized by septicemia and manifests itself in sudden losses in up to 50% of the population. There are often bruises at the base of the fins and small, punctiform bleeding ( petechiae ) in the gills . Signs of septicemia such as petechiae, mushy kidneys, and swelling of the spleen also appear in the internal organs and muscles.

The subacute form is less dramatic and causes only minor losses. A distinction is made between two forms: the form with bulging and the intestinal furunculosis:

  • In the case of furunculosis with bulging , bulges appear in the muscles, which when opened release a typical wine-red, purulent-greasy content and leave deep ulcers . Young fish often only have dark patches of skin and reddening of the fins. A secondary infection with fungi can worsen the clinical picture.
  • The intestinal furunculosis manifests itself in a bloody inflammation of the intestine (hemorrhagic enteritis ) with protrusion of the anus.

The chronic form lasts for months and often shows itself as darkening of the skin, defects in the scales and fins, and blindness and general weakness. Typical whitish lightening occurs in the area of ​​the head and back.

treatment

A definite diagnosis can only be made through a bacteriological examination . If possible, an antibiogram should be drawn up with which an effective antibiotic can be determined.

Disease prophylactic measures such as reducing the stocking density, reducing the feed ration on warm summer days, quarantine and prior control examinations of purchased fish, disinfection of eggs and equipment and the harmless disposal of dead and diseased fish are of great importance .

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