Infection of juvenile salmon Salmo salar with a Dermocystidium-like organism in Sweden

Abstract

Free spores of a Derrnocystidiurn-like organism were recovered from the epidermis and covering mucus of gills and fins of moribund farmed salmon Salmo salar. The parasite appeared in juvenile fish only and at low water temperatures (15°C). The most prominent external macroscopical clinical signs of disease were thickened fins that gave the tips a pronounced greyish opaque appearance often in combination with signs of fin rot/fin erosion. The gills were swollen and pale and could also be necrotic. Examination of fresh mounts and tissues prepared for light and electron microscopy showed vacuolated spherical spores typical for parasites of the genus Dermocystidium. Irregularly vacuolated spores with 1 or multiple nuclel were also observed. Histological examination of infected salmon indicated concurrent Flexibacter sp. infection that was venfied in Gram-negative stained imprints. The present findmg is the first observation of Dermocystidlum in Sweden. In addition, this is the first record of a Dermocystidiurn-hke agent that occurs freely in the mucus and epidermis of freshwater teleosts.

Dermocystidium sp. infection in cultured juvenile southern catfish Silurus meridionalis in China

“…Similar observations were made regarding concurrent infections of Dermocystidium spp. and bacteria by other authors (Pauley 1967, Höglund et al 1997), and Pauley (1967 thought that the bacterium was a secondary invader. Höglund et al (1997) did not determine whether the bacterium was the primary or secondary infectious pathogen.…”

“…and bacteria by other authors (Pauley 1967, Höglund et al 1997), and Pauley (1967 thought that the bacterium was a secondary invader. Höglund et al (1997) did not determine whether the bacterium was the primary or secondary infectious pathogen. However, the bacteria could be presumed to be secondary invaders in this study, because bacterial infections only occurred in the lesions caused by Dermocystidium sp.…”

“…Herr et al (1999) established a new clade called Mesomycetozoa for Rhinosporidium and DRIPs. Although controversy still exists about the taxonomic affinity of the species in the genus Dermocystidium, it is believed that the common feature of the genus is the existence of a spherical spore with a peripheral nucleus and a refractile body or large central vacuole as a stage of the developmental cycle (Höglund et al 1997, Lotman et al 2000. Dermocystidium spp.…”

Cultured Atlantic salmon in nature: a review of their ecology and interaction with wild fish

“…Damage to the rayed fins of cultured fish is caused primarily by aggressive encounters between fish involving the nipping of fins (Ellis et al, 2002), but may also result from abrasion on rough surfaces, nutritional deficiencies, and secondary bacterial infections (Höglund et al, 1997;Lellis and Barrows, 1997;Latremouille, 2003). Although such damage incurred during culture can influence fish performance, and is therefore undesirable, it can be helpful when studying social interaction in large groups of fish (MacLean et al, 2000).…”

“…damage in hatchery ParrAggressive encounters Fin damageHöglund et al, 1997;Lellis and Barrows, 1997;Ellis et al, 2002;Latremouille, 2003 Scale loss MacLean et al, 2000Lacroix and Knox, 2005 …”