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Diseases of Aquatic Organisms

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DAO 41:105-113 (2000)  -  doi:10.3354/dao041105

Isolation of the pathogen Vibrio tapetis and defense parameters in brown ring diseased Manila clams Ruditapes philippinarum cultivated in England

Bassem Allam1,*, Christine Paillard1, Alan Howard2, Marcel Le Pennec1

1Institut Universitaire Européen de la Mer, UMR 6539, Université de Bretagne Occidentale, Technopôle Brest-Iroise, 29280 Plouzané, France
2CEFAS Weymouth Laboratory, Barrack Road, The Note, DT4 8UB Weymouth Dorset, United Kingdom
*Present address: Laboratoire d¹Ecologie Animale, Université d¹Angers, 2, Boulevard Lavoisier, 49045 Angers Cedex, France. E-mail:

ABSTRACT: The Manila clam Ruditapes philippinarum was introduced for aquacultural purposes to Europe in the 1970s. In 1987, brown ring disease (BRD), caused by Vibrio tapetis, appeared in clams cultivated in Brouënou (Finistère, France) and later became increasingly widespread and was reported in cultivated and wild clams existing on the Atlantic coasts of France and Spain. The present study reports, for the first time, the presence of BRD in clams cultivated in England. The etiologic bacterium was isolated and identified using bacteriological and serological techniques. The defence response of affected clams was also studied and significant changes in the hematological and biochemical characteristics of hemolymph and extrapallial fluids were demonstrated. Significant mobilization of hemocytes toward the extrapallial fluids, in contact with the main site of infection (mantle-periostracal lamina area), was observed, suggesting a role for these pseudo-internal compartments in the preservation of clam health.

KEY WORDS: Shell disease · Bivalve · Bacteria · Immune defense · Lysozyme · Hemocyte

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