ABSTRACT: Since 1989 the presence of organic brown deposits on the inner surface of the shells of cultured manila clams Tapes philippinarum associated with episodes of high mortality has been recorded on the southern Atlantic coast of Spain. The gross signs observed in diseased clams were identical to those previously described in France as brown ring disease (BRD), caused by strains of Vibrio tapetis sp. nov. This bacterial pathogen has been isolated in several French clam production areas, and recently in BRD-affected clams cultured in Galicia (NW Spain) and Portugal, using bacteriological procedures. However, this methodology has failed to detect the pathogen in microbiological studies carried out in southwestern Spain. In the present study, an immunodetection test, based on the indirect immunofluorescence (IIF) technique, was developed, using polyclonal antisera to V. tapetis whole cells and against outer membrane (OM). This method provided evidence for the presence of the bacterium in all the BRD-affected clams analysed. V. tapetis was also detected by the same method in healthy (i.e. asymptomatic) clams, which indicates its opportunistic character.

KEY WORDS: Brown ring disease · Vibrio tapetis · Immunodetection · Microbiological analyses

Published in DAO Vol. 29, No. 3 (1997) on June 19
ISSN: 0177-5103. Copyright © Inter-Research, Oldendorf/Luhe, 1997