Categoría: Gills and Pseudobranchs

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...

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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...

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Short operculum – Gross Pathology

Gills and Pseudobranchs
by Carlos Sandoval
Figure 1. Severe opercular erosion in farmed rainbow trout.

Bone deformities occur regularly in fish farms around the world. The operculum is one of the earliest craniofacial bones to form embryologically and is subject to a range of developmental and acquired abnormalities. Opercular shortening is one of the most prevalent diseases in larval and juvenile salmonids (and other species), sometimes affecting up to 80% of fish in a population. In those species that rely on the operculum to help move water over the gills, loss of efficiency in this part of the pumping mechanism...

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Bacterial gill disease – Gross Pathology

Gills and Pseudobranchs
by Hugh Ferguson
This rainbow trout fingerling with BGD shows the typical flared opercula of respiratory distress. Note that the edge of the flared operculum is eroded. This erosion is typical of intensively-reared fish; its cause is unknown, but might be the result of higher-than-optimal bacterial enzymes in and around the branchial cavity. Whatever the cause, the consequence is a huge reduction in the ability of the animal to pump water due to elimination of the water-tight seal between the trailing edge of the operculum and the body of the fish (the cleithrum). Thus the negative pressure of the opercular pump is greatly reduced. And this in an animal that is trying to pump larger-than-normal volumes of water over its gills due to the hypoxaemia of BGD!

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...

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Epitheliocystis in Cobia – Histopathology

Gills and Pseudobranchs
by Carlos Sandoval
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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