Tenacibaculosis Histopathology

Gills and Pseudobranchs, Multisystem, Skin
by Hugh Ferguson

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...

Read More

Copper toxicity in fish

Multisystem
by Carlos Sandoval
Liver from Atlantic salmon fingerling showing positive copper reaction in hepatocyte cytoplasm. Rhodamine stain. Note the intracytoplasmic granules (bright red or rust-red) that correspond to lysosomes with sequestered excess copper (arrow).

Copper is a significant trace element necessary for the normal growth and metabolism of living organisms. However, if there is overexposure, it can be toxic. Levels of dissolved copper are often increased from anthropogenic origins such as mine washings and direct applications of algicides, molluscicides or antifouling agents. The most toxic form of copper is the cupric ion (Cu2+). Fish and crustacea are 10 to 100 times more sensitive to the toxicity of copper than mammals. For salmonids, the upper recommended limit is < 0.03...

Read More

Bacterial Kidney Disease (BKD) in Salmonids – Gross Pathology

Multisystem
by Hugh Ferguson
Atlantic salmon (adult-1500 g) with BKD. Note the multiple granulomas in kidney. These severe lesions lead to renal failure

Bacterial kidney disease (BKD) is a chronic systemic infection of salmonid fish, the cause of which is the gram-positive diplobacillus, Renibacterium salmoninarum. Although BKD is most common in salmonids, both farmed and wild, R. salmoninarum is also found in other fish species, such as cyprinids and sablefish Anoplopoma fimbria. R. salmoninarum grows intracellularly in the phagocytic cells of the fish, resulting therefore in a largely granulomatous host response, although the early response to infection does involve significant numbers of neutrophils. Clinical signs and external lesions...

Read More

Tenacibaculosis in Fish – Gross Pathology

Gills and Pseudobranchs, Multisystem, Skin
by Carlos Sandoval
Figure 1. Rainbow trout displaying tail and peduncle lesions.

Tenacibaculosis is primarily a skin infection causing ulcerative dermatitis in a range of commercially important species worldwide. Three species belonging to the genus Tenacibaculum have been associated with the disease: T. dicentrarchi, T. finnmarkense, and T. maritimum.   These bacteria are all Gram-negative and filamentous.  In marine fish, the most common isolate is T. maritimum. There is variation in the external pathological signs of the disease, depending on the species and age of the fish involved. Different names have been used for this usually ulcerative dermatitis; they include salt water columnaris...

Read More

Gas Bubble Disease

Multisystem
by Hugh Ferguson
Figure 1. Rainbow trout with several gas bubbles in the anterior chamber. Note the haemorrhage both dorsally and ventrally, the latter “coning” through the ventral iris pore

Gas bubble disease (GBD) is the fish equivalent of the “bends” in human scuba divers. It is the result of gas coming out of solution in the bloodstream, thereby leading to the formation of emboli, especially in smaller blood vessels, including rete. Thus, lesions are common in gills, and the choroid gland of the eye. In water that is supersaturated, fish equilibriate with that supersaturated gas, just as human scuba divers equilibriate with gas at high pressures. It is not known precisely what prompts the...

Read More
totop