Furunculosis is a bacterial disease of salmonids. It is usually characterized by boils or furuncles on the skin of affected fish although this is not always the case. If there are multiple heads, the lesion is called a ‘carbuncle’. Large boils form abscesses, defined as an accumulation of pus within a cavity. Cellulitis may also occur, i.e. infection of the surrounding tissues, and this may cause fever and illness. This disease infects salmon species worldwide, with both typical and atypical strains causing disease.
Furunculosis is an infection of hair follicles caused by a common skin bacterium. Individuals with diabetes are prone to recurrent episodes of furunculosis. Most people with boils are otherwise healthy and have good personal hygiene. They do however carry Staph. aureus on the surface of their skins (Staph. carrier state). Why this occurs is usually not known, but it is estimated that 10- 20% of the population are Staph.
The pain may be reported to extend up the side of the head or as far down as the neck. Detection of the furuncle is rather simple.
Common sign of this disease in animals are-
- furuncles (or boils) causing deep abscesses, usually in adult salmon in the acute phase of infection
- haemorrhages on skin, mouth and fin bases (mainly paired fins)
- darkening of body colour
Topical medication can be applied, such as hydrogen peroxide, or formalin/formaldehyde solutions, or used as a bath/dip. Antibiotics, particularly those that can be absorbed internally.
Your physician may incise and drain the furuncle when the skin over the furuncle becomes thin and the mass underneath is soft. Without treatment, the furuncle will heal in 10-20 days. With treatment, furuncles will heal in less time and symptoms will be less severe. A potential complication of treatment is that the pus that drains when the furuncle opens spontaneously may contaminate nearby skin, causing new furuncles.
Treatment with antibiotics and/or antibiotic nasal cream may clear Staphylococcus bacteria from 'carriers' and reduce the chance of boils, or other types of skin infection, from recurring.