Brown ring disease (BRD) in Ruditapes philippinarum and Ruditapes decussatus is a shell disease caused by Vibrio tapetis. This
disease has begun in 1987 in clams beds in Brittany (France) and then has
spread along the European Atlantic coast. Since about fifteen years,
research on BRD has progress a lot and the purpose of this review is to give
a short description of BRD in clams in retrospect and in addition of recent
and pertinent results. Diagnosis including isolation, biochemical,
serological and molecular characterization has been developed to identify
and detect the pathogen. Therefore, Vibrio tapetis-like strains has been detected in other host
specie, in cultured fishes during mortalities, such as the wrasse,
Symphodus melops in Norway and the halibut, Hippoglossus hippoglossus in Scotland. Mechanisms of host-pathogen
interactions modulated by environmental factors were studied using in vivo
bacterial challenge and in vitro bio-assays. According to these studies, adherence
and cytotoxic factors have been yet identified as virulence factors;
identification and characterization of virulence genes are in progress.
Field and experimental studies confirmed the significant effect of
temperature on the development of BRD and on clam defense related
activities. A significant increase in temperature over 21 °C may have a
preventive effect on the development of the disease.