A prominent feature of chronic inflammation is the
presence of melanomacrophages or macrophage aggregates
that are normally located in the stroma of the haematopoietic
tissue of the kidney, liver and spleen. Chronic inflammation
is characterized by cellular proliferation rather than exudation, and comprises resorption, formation of granulation
tissue and fibrosis. Granulomatous inflammation, a distinctive pattern of chronic inflammation, and fibrinous
epicarditis are recurrent findings in conditions such as bacterial kidney disease and mycobacteriosis (Fig. 4.13).
Regardless of the origin of these inflammatory responses,
granulomatous inflammation tissue may have resemblance
to neoplastic changes.
Ulceration involves necrosis and an eroded epithelial
surface with underlying acute and chronic inflammation
following many types of tissue injury. Necrotic tissue takes
on a different colour and consistency and dependent upon
the age of the lesion and the quantity of blood. Focal necrosis
develops to an ulcer when tissue is sloughed from the area.
Once the epidermis is breached, loss of fluid, swelling,
haemorrhage necrosis and potential involvement of secondary pathogens occur. An ulcer that starts from the epithelium
often have a base-narrow shape, conversely an ulcer that
begins as a lesion below the surface tends to be ‘basewide’. The inflammatory response is the start of the healing
process and the skin shows a capacity for repair with hypertrophy, fibrosis and regeneration of the damaged tissue or
scar formation. Damaged scales seldom recover their original pattern and newly formed scales are usually smaller and
undulated and therefore easy to identify. In some cases of
extensive tissue loss, a cavity may simply remain at the site
of injury.
Exophthalmia refers to an excessive protrusion of the
posterior aspects of the ocular globe and occur in several
diseases. It is usually the result of increased intraocular
pressure, inflammation in the well-vascularised rete behind
the eye with resultant swelling, oedema and loss of connective tissue or granulomatous inflammation. These are common findings in moribund fish, occasionally with associated
haemorrhage but overall non-specific clinical signs
(Fig. 4.14). Histologically, oedema, infiltration of
macrophages in the retrobulbar area, swelling and necrosis
can be observed. A progressive panophthalmitis is primarily
associated with bacterial infections and refers to inflammation of all coats of the eye including intraocular structures.
Eosinophilic granular cells (EGCs), also known as mast
cells are present in most species of teleosts in a variety
of tissues, including the gut, gills (Fig. 4.15), skin, brain,
and surrounding major blood vessels. Acute tissue
Fig. 4.13 Idiopathic highly cellular epicarditis in adult farmed Atlantic salmon. Martius, scarlet blue (MSB) stain
Fig. 4.14 (a) Eye haemorrhage in adult farmed Atlantic salmon. (b) Exophthalmia in wild grayling
4.1 Inflammation and Proliferation
43
presence of melanomacrophages or macrophage aggregates
that are normally located in the stroma of the haematopoietic
tissue of the kidney, liver and spleen. Chronic inflammation
is characterized by cellular proliferation rather than exudation, and comprises resorption, formation of granulation
tissue and fibrosis. Granulomatous inflammation, a distinctive pattern of chronic inflammation, and fibrinous
epicarditis are recurrent findings in conditions such as bacterial kidney disease and mycobacteriosis (Fig. 4.13).
Regardless of the origin of these inflammatory responses,
granulomatous inflammation tissue may have resemblance
to neoplastic changes.
Ulceration involves necrosis and an eroded epithelial
surface with underlying acute and chronic inflammation
following many types of tissue injury. Necrotic tissue takes
on a different colour and consistency and dependent upon
the age of the lesion and the quantity of blood. Focal necrosis
develops to an ulcer when tissue is sloughed from the area.
Once the epidermis is breached, loss of fluid, swelling,
haemorrhage necrosis and potential involvement of secondary pathogens occur. An ulcer that starts from the epithelium
often have a base-narrow shape, conversely an ulcer that
begins as a lesion below the surface tends to be ‘basewide’. The inflammatory response is the start of the healing
process and the skin shows a capacity for repair with hypertrophy, fibrosis and regeneration of the damaged tissue or
scar formation. Damaged scales seldom recover their original pattern and newly formed scales are usually smaller and
undulated and therefore easy to identify. In some cases of
extensive tissue loss, a cavity may simply remain at the site
of injury.
Exophthalmia refers to an excessive protrusion of the
posterior aspects of the ocular globe and occur in several
diseases. It is usually the result of increased intraocular
pressure, inflammation in the well-vascularised rete behind
the eye with resultant swelling, oedema and loss of connective tissue or granulomatous inflammation. These are common findings in moribund fish, occasionally with associated
haemorrhage but overall non-specific clinical signs
(Fig. 4.14). Histologically, oedema, infiltration of
macrophages in the retrobulbar area, swelling and necrosis
can be observed. A progressive panophthalmitis is primarily
associated with bacterial infections and refers to inflammation of all coats of the eye including intraocular structures.
Eosinophilic granular cells (EGCs), also known as mast
cells are present in most species of teleosts in a variety
of tissues, including the gut, gills (Fig. 4.15), skin, brain,
and surrounding major blood vessels. Acute tissue
Fig. 4.13 Idiopathic highly cellular epicarditis in adult farmed Atlantic salmon. Martius, scarlet blue (MSB) stain
Fig. 4.14 (a) Eye haemorrhage in adult farmed Atlantic salmon. (b) Exophthalmia in wild grayling
4.1 Inflammation and Proliferation
43