Post 9: Marine Velvet Disease

Marine Velvet disease (Amyloodinium ocellatum) is a microscopic, parasitic protista in the phylum dinoflagellata (Brown & Hovasse 1946). Mass mortalities resulting from A. ocellatum have been documented since the 1930's with the parasite infecting fish in both fresh and salt water; tolerating salinity levels from 3-45 ppt (Paperna 1980).

A. ocellatum has a 3 stage life-cycle, beginning as a trophont (The feeding stage of its life cycle). The trophont then matures into a reproductive tomont which produces the third stage in the life cycle; the free swimming dinospores-which can survive up to a week whilst looking for a host organism (Paperna 1980).

A fish with A. occeltatum can be visually diagnosed in an aquarium or aquaculture environment by the infected fish 'flashing' against the substrate and/or gasping for air at the surface as it suffers from anoxia due to A. ocellatum occuring on the gills of the host fish (Lawler 1980). In the later stages, the skin of infected fish may appear powdery (appearing as if it has been rolled in flour) as the Marine Velvet disease can cause signficant damage to the hosts skin and fins (Lawler 1980).

Copper is an effective treatment to aquatic parasites and fungi and is popular for treatment of A. ocellatum, in the form of copper sulfate. A knowledge of the water chemistry such as pH levels in the hosts surrounding water body should be known to avoid potential copper toxicity (Cardeilhac & Whitaker 1988). Therefore knowing the concentrations of copper in the administering treatment and the volume of water in the tank is recommended for this treatment process.

Amyloodinium ocellatum can be diagnosed from observed powedery skin

  
     

References:

Brown, E. Hovasse, R 1946, 'Amyloodinium ocellatum (Brown), A Peridinian Parasitic on Marine Fishes. A Complementary Study', 'Journal of Zoology', vol. 116, pp. 33-46

Cardeilhac, P. Whitaker, B 1988, 'Copper Treatments: Uses and Precautions', 'Veterinary Clinics of North America: Small Animal Practice', vol. 18, pp. 435-448

Lawler, A 1980, 'Studies on Amyloodinium ocellatum (Dinoflagellata) in Mississippi Sound: Natural and Experimental Hosts', 'Gulf and Carribean Research', vol. 6, pp. 403-413

Paperna, I 1980, 'Amyloodinium ocellatum (Brown, 1931) (Dinoflagellida) Infestations in Cultured Marine Fish at Eilat, Red Sea: Epizootiology and Pathology', 'Journal of Fish Diseases', vol. 3, pp. 363-372