Nephrocalcinosis in Fish – Gross pathology

Figure 1. Gross appearance of nephrocalcinosis. The kidney is swollen and grey with an irregular surface and white mineral deposits in the ureters.

Nephrocalcinosis (or urolithiasis) in fish is a chronic inflammatory condition of unknown aetiology in which calcium and other minerals precipitate as hydroxyapatite within the distal renal tubules and collecting ducts. The disease usually records low mortality and although food conversion efficiency is probably impaired, the major concern about the condition centres round a reduction in carcase quality at slaughter. In severe cases, the muscle dorsal to the kidney may also be affected. There are some predisposing factors for this condition like high levels of carbon...

SPINAL FRACTURE DUE TO ELECTRIC SHOCK

Atlantic salmon, presmolt, FW, exposed to electric shock. Note the spinal fracture associated haemorrhage. The cause of the electric shock was an energized cable that fell into the tank.

Bone is a highly anisotropic, viscoelastic material that has the ability to continually adapt to changes in its physiological or mechanical environment. The capacity of bone to resist mechanical forces and fractures depends not only on the quantity of bone tissue but also on its quality. Bone is a composite material, made from a collagenous matrix and from minerals. The collagenous matrix provides toughness (fracture resistance) and the minerals increase the bone’s stiffness (bending resistance). By itself, the mineral phase is brittle and fractures easily....

Gastric dilation & Air sacculitis or “Bloat” in salmonids – Gross Pathology

Chinook salmon with “Bloat”. Note the severe abdominal distention.

Bloat is a non-infectious condition of salmonids where the abdomen is abnormally distended by an enlarged, fluid-filled stomach. The wall of the enlarged stomach wall is thin and flaccid. Occasionally the swimbladder is also affected.   The condition is seen in salmonids reared in sea water and fed fishmeal-based pelleted rations. While it has been reported occasionally in Atlantic salmon (Salmo salar L.) members of the genus Oncorhynchus are more susceptible. These include Rainbow trout (O. mykiss), Chinook salmon (O. tshawytscha), and Coho salmon (O....

Cataracts in Salmonids – Gross Pathology

Atlantic salmon with cataract. Note that the opacity occupies more than 75% of the lens.

Cataracts are changes in the clarity of the lens so that it appears cloudy. Such changes are a clinical or gross diagnosis, and there may be no histopathological correlate. Nevertheless, opacity of the lens results in reduced ability to see. Cataracts may be divided into primary or secondary disease. In primary cataract, opacity of the lens is the only sign of disease in the eye, while in secondary cataract the lens changes occur as a consequence of other intraocular disease. A wide variety of causes...

Epitheliocystis in Cobia – Histopathology

Cobia, gill: abundant lamellar basophilic inclusions are observed, consistent with severe epitheliocystis infection H&E

Aquaculture of cobia (Rachycentrum canadum) has gained popularity in the last decade, and this species is now farmed in several countries in Latin America and Asia. Epitheliocystis is a chlamydia or rickettsia-like organism infecting the gills and skin of a variety of species in both fresh and saltwater. The disease has been reported in at least 90 species of marine and freshwater fish in both the southern and northern hemispheres. At least four bacterial species may be involved in this condition: Candidatus Piscichlamydia salmonis (Salvelinus...

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