Cardiomyopathy syndrome in Atlantic salmon (CMS) – Histopathology

CMS in ventricle of Atlantic salmon showing severe myocarditis of spongy layer. Note that the compact layer (on the left) is largely unaffected.

Cardiomyopathy syndrome (CMS) is a severe cardiac disease affecting Atlantic salmon characterized by prolonged periods of usually low-level mortalities. The disease was first recognized in farmed Atlantic salmon in Norway in 1985 and subsequently in farmed salmon in the Faroe Islands, Scotland and Ireland. CMS is a transmissible disease that has been causally linked to the Piscine Myocarditis Virus (PMCV), closely allied to the Totiviridae. CMS usually causes mortality in adult or maturing fish after 12 to 18 months in seawater, resulting in substantial economic...

Bacterial gill disease – Gross Pathology

Figure 1. Intensively-reared goldfish with sub-acute/chronic BGD. Note the pale areas of hyperplasia and fusion within the gills (arrow). Although salmonids are most commonly affected, other species are also susceptible.

Bacterial gill disease (BGD) occurs in several species, but it is an especially serious problem of intensive salmonid culture, and in some parts of the world it is the most common disease, especially in fry and fingerlings. BGD is characterized by explosive morbidity and mortality rates, attributable to bacterial colonization of gill surfaces. Despite such pronounced clinical signs and high mortality, pathological changes are surprisingly few and hard to find in the acute disease. It is only when (if) the fish survive for a few...

Jellyfish Lesions in Fish – Histopathology

Figure 5. Phialella quadrata attached to gill raker of Atlantic salmon and showing necrosis of epithelium, loss of basement membrane, and underlying dermal haemorrhage. A close inspection of the interface between the jellyfish and the gill epithelium shows tube-like extensions reaching down through the epithelium – nematocysts?

The negative interactions between jellyfish and fish in aquaculture appear to be an increasing problem. This is partly due to increased numbers of jellyfish, associated with global warming, reduced numbers of their predators, and to the intensification of aquaculture operations in many coastal areas worldwide. Most reported problems have occurred in marine-farmed salmonids in northwest Europe. Nevertheless, aquaculture operations in other regions such as Asia, North America, and Australia have also been affected. Jellyfish involved are primarily cnidarians i.e. those species with stinging cells –...

Proliferative Kidney Disease in Salmonids (PKD) – Gross Pathology

Rainbow trout with PKD. There is a marked hyperplasia of interstitium with the kidney thrown into bulbous ridges. The reddening is tge result of secondary yersinia infection.

Proliferative kidney disease (PKD) is an endoparasitic disease of salmonid fish caused by Tetracapsuloides bryosalmonae (Myxozoa: Malacosporea).  This chronic, largely renal interstitial disease is caused by the extraporogonic but intracellular stages of the parasite, which cause a severe granulomatous host response. The severity of the disease is linked to water temperature, with roughly 15 degrees °C as the cut-off: below that temperature, lesions and clinical disease are minimal. Above that temperature, however, lesions can be severe and mortality high. Inevitably, global warming has resulted in...

Cardiomyopathy syndrome (CMS) – Gross Pathology

Figure 2. Salmon with CMS. Necrosis in the atrium of this fish has been so severe that it has ruptured. Note that the ventricle appears normal, due only to the fact that the compact layer remains largely unaffected.

Cardiomyopathy syndrome (CMS), is a severe heart disease of Atlantic salmon.  This transmissible condition has been diagnosed in several countries, especially Norway, where it was first reported, but also Scotland, Ireland and the Faroes. It is causally linked to the Piscine Myocarditis Virus (PMCV), closely allied to the Totiviridae. Typically, CMS occurs in the biggest, fastest-growing fish that never go off their feed – indeed their stomach is usually full of pellets when they suddenly die! Brood stock are also susceptible. This disease has an...

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