Pancreatic acinar tissue is involved in most of the economically important virus diseases of salmonids, especially infectious pancreatic necrosis (IPN) (Sadasiv, 1995), pancreas disease (PD) ( Munro et al., 1984, Ferguson et al., 1986., Murphy et al., 1992, McLoughlin et al., 1996) infectious haematopoietic necrosis (IHN) (Yasutake & Amend 1972) and in catfish, channel catfish virus (CCV). Acinar tissue damage of varying severity has been described associated with all these viral infections. Herpes salmonis virus produces acinar cell syncytia which are pathognomonic for this infection. (Wolf & Smith, 1981). In all of these infections other organs may also be damaged during a disease outbreak. Focal or diffuse pancreatic necrosis is common in the above infections, with necrotic cells undergoing pyknosis, karyolysis and karyorrhexis, with release of cytoplasmic contents into the surrounding connective tissue. There can be a variable inflammatory response to the pancreatic acinar cell necrosis, varying from a mild mononuclear cell infiltrate to severe post-necrotic fibrosis involving all of the surrounding mesenteric fat. Depending on the extent of this fibrous reaction, acinar cell regeneration appears possible following many viral infections.

Infectious pancreatic necrosis (IPN) showing areas of focal
necrosis. Note the slight increase in a loose fibrous network
and the intact fat body. Atlantic salmon.

IPN causing pancreatic necrosis.


Salmon Pancreas disease leading to the absence of acinar tissue with
slight infiltration. Note depleted fat body. Farmed Atlantic salmon.

Salmon Pancreas disease. High magnification.
Farmed Atlantic salmon.


Sleeping disease causing pancreatic atrophy. Rainbow trout.

Sleeping disease. Note degeneration of pancreatic acini.

Acinar cells can also become atrophied as a result of prolonged starvation and in vitamin C deficiency. Atrophied pancreatic cells have markedly reduced numbers of zymogen granules and the cell size is diminished. However reduced numbers in zymogen granules m the absence of reduced cell size may simply indicate that the fish fed shortly before death. The clinical history of the fish needs to be considered in interpretation of this type of finding.

Winter disease. Note the dramatic atrophy of pancreatic acini around
portal vessels in the liver. Gilthead seabream (Sparus aurata).

Steatitis or pansteatitis is an inflammation of the visceral fatty tissue including the peripancreatic fat. Histologically the fat cell walls are thickened with a variable infiltration with inflammatory cells plus or minus pigment deposits. This lesion may occur as a sequel to pancreatitis and has been described associated with vitamin E and /or rancid fat in the diet. (Roberts et al .,1976).

Because of its rich blood supply the pancreas can also be colonized in bacteraemias such as furunculosis, bacterial kidney disease (BKD) and in granulomatous diseases such as mycobacteriosis.

Bacterial Kidney Disease (BKD). Natural systemic infection.
Gram Stain. Chinook Salmon.

Bacterial Kidney Disease (BKD). Natural systemic infection.
Gram Stain. Chinook Salmon.

Numerous parasitic infections may also involve the pancreas including, Eimeria species, Myxobolus and microsporidian species and digenic metacercaria to name but a few.

Granulomatous lesions in and around the pancreas have been associated with intra-peritoneal use of oil-adjuvanted vaccines for vibriosis and furunculosis infections in salmon. (Poppe and Breck 1997). These are characterized by the presence of numerous macrophages and eosinophilic granular cells within a severe peripancreatic inflammatory reaction. Oil deposits can often be distinguished as circular spaces within the inflammatory reaction.


Post vaccination lesions in post smolt Atlantic salmon. Pancreatic
atrophy and chronic inflammatory response, including giant
cells and melanin deposits, can be seen.


Post vaccination (ip injection against Aeromonas salmonicida,
Vibrio anguillarum, Vibrio salmonicida and IPN) lesions in
post smolt Atlantic salmon. Pancreatic atrophy
and melanin can be seen.

Pancreatic lesions have also been described associated with crude oil spills.

Sekoke disease of intensively reared carp results in a spontaneous diabetes which has been associated with rancidity due to the incorporation of significant levels of silkworm pupae in the diet. It is characterized by severe emaciation, skin haemorrhages, changes in the beta cells of the islets of Langerhans and kidney, muscle and liver changes. (Yokote, 1970).