Aluminium Toxicity in Fish – Histopathological Findings

Deposition of aluminium in gills leads to chloride cell necrosis or at lower levels, to inhibition of the enzymes carbonic anhydrase and/or gill NA+, K+ – ATPase (NKA), required for seawater tolerance. Such changes impair osmoregulatory capacity and cause physiological stress due to disruption of gas and ion transport, altered blood chemistry and hormonal imbalance.

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Saprolegnia Infection in Fish – Gross Pathology and Histopathology

Saprolegnia often presents as a secondary infection that is diagnosed by the appearance of white or grey cotton-like tufts that, when out of water, have a somewhat mucoid appearance. Typical disease signs are visible circular or crescent-shaped, cotton-wool like, white or grey patches of filamentous mycelia on the fish skin. The lesions appear mainly around the head and the caudal, adipose and anal fins. Lesions may spread over the body until adjacent lesions coalesce.

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Cataracts in Fish – Gross Pathology and Histopathology

We have recently seen a high incidence of cataracts in farmed salmon in several European countries, Canada, and Chile. Salmonids depend on vision for normal feed intake and, not surprisingly, cataracts have been shown to reduce feed conversion efficiency and growth rates, which ultimately raise the cost of rearing fish. Consequently, cataracts can have a significant economic impact on salmonid aquaculture. It is important to note at the outset that “cataracts” is a clinical definition, and their presence does not necessarily mean that changes can...

Infectious Salmon Anaemia (ISA) – Gross Pathology

Infectious salmon anaemia (ISA) is a disease caused by infectious salmon anaemia virus (ISAV), genus Isavirus, family Orthomyxoviridae that affects primarily marine-farmed Atlantic salmon (Salmo salar). Recorded for the first time in 1984 in Norway, it still causes recurrent epidemic outbreaks in Chile. The disease is present in most countries that farm Atlantic salmon: Norway, Scotland, Ireland, Faroe Islands, Canada, USA, and Chile. The virus is adapted to cold-water salmonid fish and has an optimum growth at 15°C. Atlantic salmon is the only species known...

Tenacibaculosis Histopathology

Tenacibaculosis is a serious bacterial disease affecting a great variety of marine fish, especially those species under culture conditions, causing necrotic lesions on the body. Gross pathological signs vary according to the species and age of fish involved. Characteristic clinical signs are ulcerative skin lesions, mouth erosion and ulceration, and fraying of fins and tail. In general, it is mainly a superficial infection, but some isolates are highly toxigenic, and systemic disease can therefore result, involving different internal organs. Several species of Tenacibaculum can be...

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