During recent years, investigations on decrease of rotifer density in culture tanks from several hatcheries have shown that infectious diseases might be associated with abnormal mortality. The first reported infection was caused by an unusual birnavirus referred as rotifer birnavirus (RBV). Viral lesions appeared in cells of gastric glands and spread to other epithelia. Virus particles were also found within ovarian cells. Highly infected rotifers exhibited abnormal behavior and died. The second important pathogen found in Brachionus plicatilis has been provisionally related to the Lagenidiaceae. The fungus developed in up to 85% of rotifers and caused sudden, precipitous decrease in animal density. The occurrence of these diseases shows that in the future infectious agents will have to be considered as important factors capable of reducing the productivity of rotifer mass cultures.
(IFREMER, GIE, RA, Chemin Maguelone, F-34250 Palavas Les Flots, France)
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